Struct BoxConsumer 

pub struct BoxConsumer<T> { /* private fields */ }

BoxConsumer struct

Consumer implementation based on Box<dyn FnMut(&T)> for single ownership scenarios. When sharing is not needed, this is the simplest and most efficient consumer type.

Features

• Single Ownership: Not cloneable, transfers ownership when used
• Zero Overhead: No reference counting or lock overhead
• Mutable State: Can modify captured environment through FnMut
• Builder Pattern: Method chaining naturally consumes self

Use Cases

Choose BoxConsumer when:

• Consumer is used only once or in a linear flow
• Building pipelines where ownership flows naturally
• No need to share consumers across contexts
• Performance critical and cannot accept sharing overhead

Performance

BoxConsumer has the best performance among the three consumer types:

• No reference counting overhead
• No lock acquisition or runtime borrowing checks
• Direct function calls through vtable
• Minimal memory footprint (single pointer)

Examples

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let mut consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});
consumer.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

Author

Hu Haixing

Implementations

impl<T> BoxConsumer<T>

where T: 'static,

pub fn new<F>(f: F) -> Self

where F: FnMut(&T) + 'static,

Create a new BoxConsumer

Type Parameters

• F - Closure type

Parameters

• f - Closure to wrap

Return Value

Returns a new BoxConsumer<T> instance

Examples

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let mut consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x + 1);
});
consumer.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![6]);

Examples found in repository

examples/consumer_fn_usage.rs (lines 23-25)

fn main() {
    println!("=== Consumer into_fn/to_fn Usage Examples ===\n");

    // Example 1: Using BoxConsumer::into_fn to pass to standard library's map
    println!("1. BoxConsumer::into_fn used with Iterator::for_each");
    let log = Arc::new(Mutex::new(Vec::new()));
    let l = log.clone();
    let consumer = BoxConsumer::new(move |x: &i32| {
        l.lock().unwrap().push(*x * 2);
    });

    // Convert consumer to closure and pass to for_each
    [1, 2, 3, 4, 5].iter().for_each(consumer.into_fn());
    println!("   Result: {:?}\n", *log.lock().unwrap());

    // Example 2: Using ArcConsumer::to_fn can be used multiple times
    println!("2. ArcConsumer::to_fn can be used multiple times");
    let log2 = Arc::new(Mutex::new(Vec::new()));
    let l2 = log2.clone();
    let consumer2 = ArcConsumer::new(move |x: &i32| {
        l2.lock().unwrap().push(*x + 10);
    });

    // to_fn doesn't consume consumer, can be called multiple times
    [1, 2, 3].iter().for_each(consumer2.to_fn());
    println!("   First time: {:?}", *log2.lock().unwrap());

    [4, 5].iter().for_each(consumer2.to_fn());
    println!("   Second time: {:?}\n", *log2.lock().unwrap());

    // Example 3: Using RcConsumer::to_fn
    println!("3. RcConsumer::to_fn used for single-threaded scenarios");
    let log3 = Rc::new(RefCell::new(Vec::new()));
    let l3 = log3.clone();
    let consumer3 = RcConsumer::new(move |x: &i32| {
        l3.borrow_mut().push(*x * 3);
    });

    [1, 2, 3, 4].iter().for_each(consumer3.to_fn());
    println!("   Result: {:?}\n", *log3.borrow());

    // Example 4: Using in custom functions
    println!("4. Using in custom functions");
    fn process_items<F>(items: Vec<i32>, consumer: F)
    where
        F: FnMut(&i32),
    {
        items.iter().for_each(consumer);
    }

    let log4 = Arc::new(Mutex::new(Vec::new()));
    let l4 = log4.clone();
    let consumer4 = BoxConsumer::new(move |x: &i32| {
        l4.lock().unwrap().push(*x * 5);
    });

    // Use into_fn to convert Consumer to closure and pass to function
    process_items(vec![1, 2, 3], consumer4.into_fn());
    println!("   Result: {:?}\n", *log4.lock().unwrap());

    // Example 5: Using into_fn after chained operations
    println!("5. Using into_fn after chained operations");
    let log5 = Arc::new(Mutex::new(Vec::new()));
    let l5 = log5.clone();
    let l6 = log5.clone();

    let chained = BoxConsumer::new(move |x: &i32| {
        l5.lock().unwrap().push(format!("A: {}", x));
    })
    .and_then(move |x: &i32| {
        l6.lock().unwrap().push(format!("B: {}", x));
    });

    [1, 2].iter().for_each(chained.into_fn());
    println!("   Result: {:?}\n", *log5.lock().unwrap());

    println!("=== Demo Complete ===");
}

examples/consumer_demo.rs (lines 33-35)

fn main() {
    println!("=== Consumer Examples ===\n");
    println!("Note: Consumer only reads values, does not modify the original value");
    println!("If you need to modify values, please refer to mutator_demo.rs\n");

    // ========================================================================
    // Example 1: BoxConsumer basic usage
    // ========================================================================
    println!("Example 1: BoxConsumer basic usage");
    println!("{}", "-".repeat(50));

    let mut consumer = BoxConsumer::new(|x: &i32| {
        println!("Read and calculate: {} * 2 = {}", x, x * 2);
    });
    let value = 5;
    println!("Value: {}", value);
    consumer.accept(&value);
    println!("Value remains: {} (not modified)\n", value);

    // ========================================================================
    // Example 2: BoxConsumer method chaining
    // ========================================================================
    println!("Example 2: BoxConsumer method chaining");
    println!("{}", "-".repeat(50));

    let results = Arc::new(Mutex::new(Vec::new()));
    let r1 = results.clone();
    let r2 = results.clone();
    let r3 = results.clone();

    let mut chained = BoxConsumer::new(move |x: &i32| {
        r1.lock().unwrap().push(*x * 2);
    })
    .and_then(move |x: &i32| {
        r2.lock().unwrap().push(*x + 10);
    })
    .and_then(move |x: &i32| {
        r3.lock().unwrap().push(*x);
        println!("Processing value: {}", x);
    });

    let value = 5;
    println!("Initial value: {}", value);
    chained.accept(&value);
    println!("Collected results: {:?}", *results.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 3: Closure extension methods
    // ========================================================================
    println!("Example 3: Direct use of extension methods on closures");
    println!("{}", "-".repeat(50));

    let result = Arc::new(Mutex::new(0));
    let r1 = result.clone();
    let r2 = result.clone();

    let mut closure_chain = (move |x: &i32| {
        *r1.lock().unwrap() = *x * 2;
    })
    .and_then(move |_x: &i32| {
        *r2.lock().unwrap() += 10;
    });

    let value = 5;
    println!("Initial value: {}", value);
    closure_chain.accept(&value);
    println!("Calculation result: {}", *result.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 4: BoxConsumer factory methods
    // ========================================================================
    println!("Example 4: BoxConsumer factory methods");
    println!("{}", "-".repeat(50));

    // noop
    println!("noop - does nothing:");
    let mut noop = BoxConsumer::<i32>::noop();
    let value = 42;
    noop.accept(&value);
    println!("Value: {}\n", value);

    // print
    print!("print - prints value: ");
    let mut print = BoxConsumer::new(|x: &i32| println!("{}", x));
    let value = 42;
    print.accept(&value);
    println!();

    // print with prefix
    let mut print_with = BoxConsumer::new(|x: &i32| println!("Value is: {}", x));
    let value = 42;
    print_with.accept(&value);
    println!();

    // ========================================================================
    // Example 5: Conditional Consumer
    // ========================================================================
    println!("Example 5: Conditional Consumer");
    println!("{}", "-".repeat(50));

    // when
    let mut check_positive =
        BoxConsumer::new(|x: &i32| println!("Positive: {}", x)).when(|x: &i32| *x > 0);

    let positive = 5;
    let negative = -5;
    print!("Check {}: ", positive);
    check_positive.accept(&positive);
    print!("Check {}: ", negative);
    check_positive.accept(&negative);
    println!("(negative numbers not printed)\n");

    // when().or_else()
    let mut categorize = BoxConsumer::new(|x: &i32| println!("Positive: {}", x))
        .when(|x: &i32| *x > 0)
        .or_else(|x: &i32| println!("Non-positive: {}", x));

    let positive = 10;
    let negative = -10;
    categorize.accept(&positive);
    categorize.accept(&negative);
    println!();

    // ========================================================================
    // Example 6: ArcConsumer - multi-threaded sharing
    // ========================================================================
    println!("Example 6: ArcConsumer - multi-threaded sharing");
    println!("{}", "-".repeat(50));

    let shared = ArcConsumer::new(|x: &i32| println!("Processing value: {}", x * 2));

    // Clone for another thread
    let shared_clone = shared.clone();
    let handle = thread::spawn(move || {
        let value = 5;
        let mut consumer = shared_clone;
        consumer.accept(&value);
        value
    });

    // Use in main thread
    let value = 3;
    let mut consumer = shared;
    consumer.accept(&value);

    let thread_result = handle.join().unwrap();
    println!("Thread result: {}\n", thread_result);

    // ========================================================================
    // Example 7: ArcConsumer composition (does not consume original consumer)
    // ========================================================================
    println!("Example 7: ArcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = ArcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = ArcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    // Composition does not consume original consumer
    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);

    // double and add_ten are still available
    let value3 = 10;
    let mut d = double;
    print!("Original double still available, processing 10: ");
    d.accept(&value3);
    println!();

    // ========================================================================
    // Example 8: RcConsumer - single-threaded sharing
    // ========================================================================
    println!("Example 8: RcConsumer - single-threaded sharing");
    println!("{}", "-".repeat(50));

    let rc_consumer = RcConsumer::new(|x: &i32| println!("Processing: {}", x * 2));

    // Clone multiple copies
    let clone1 = rc_consumer.clone();
    let clone2 = rc_consumer.clone();

    let value1 = 5;
    let mut c1 = clone1;
    print!("clone1 processing 5: ");
    c1.accept(&value1);

    let value2 = 3;
    let mut c2 = clone2;
    print!("clone2 processing 3: ");
    c2.accept(&value2);

    let value3 = 7;
    let mut c3 = rc_consumer;
    print!("Original processing 7: ");
    c3.accept(&value3);
    println!();

    // ========================================================================
    // Example 9: RcConsumer composition (borrowing &self)
    // ========================================================================
    println!("Example 9: RcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = RcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = RcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);
    println!();

    // ========================================================================
    // Example 10: Unified Consumer trait
    // ========================================================================
    println!("Example 10: Unified Consumer trait");
    println!("{}", "-".repeat(50));

    fn log_all<C: Consumer<i32>>(consumer: &mut C, values: &[i32]) {
        for value in values.iter() {
            consumer.accept(value);
        }
    }

    let values = vec![1, 2, 3, 4, 5];

    let mut box_con = BoxConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("BoxConsumer processing {:?}: ", values);
    log_all(&mut box_con, &values);
    println!();

    let mut arc_con = ArcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("ArcConsumer processing {:?}: ", values);
    log_all(&mut arc_con, &values);
    println!();

    let mut rc_con = RcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("RcConsumer processing {:?}: ", values);
    log_all(&mut rc_con, &values);
    println!();

    let mut closure = |x: &i32| print!("{} ", x * 2);
    print!("Closure processing {:?}: ", values);
    log_all(&mut closure, &values);
    println!("\n");

    // ========================================================================
    // Example 11: Data validation and logging
    // ========================================================================
    println!("Example 11: Data validation and logging");
    println!("{}", "-".repeat(50));

    let validator = BoxConsumer::new(|x: &i32| {
        let status = if *x >= 0 && *x <= 100 {
            "valid"
        } else {
            "out of range"
        };
        println!("Validate {}: {}", x, status);
    });

    let logger = BoxConsumer::new(|x: &i32| {
        println!("Log to file: value={}, square={}", x, x * x);
    });

    let mut pipeline = validator.and_then(logger);

    let test_values = vec![-50, 30, 200];
    for value in test_values {
        pipeline.accept(&value);
    }
    println!();

    // ========================================================================
    // Example 12: String analysis
    // ========================================================================
    println!("Example 12: String analysis");
    println!("{}", "-".repeat(50));

    let mut string_analyzer = BoxConsumer::new(|s: &String| {
        println!("Length: {}", s.len());
    })
    .and_then(|s: &String| {
        println!("Lowercase: {}", s.to_lowercase());
    })
    .and_then(|s: &String| {
        println!("Uppercase: {}", s.to_uppercase());
    })
    .and_then(|s: &String| {
        let word_count = s.split_whitespace().count();
        println!("Word count: {}", word_count);
    });

    let text = String::from("Hello World");
    println!("Analyzing text: \"{}\"", text);
    string_analyzer.accept(&text);
    println!("Original text: \"{}\" (not modified)\n", text);

    // ========================================================================
    // Example 13: Type conversion
    // ========================================================================
    println!("Example 13: Type conversion");
    println!("{}", "-".repeat(50));

    // Closure -> BoxConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut box_con = closure.into_box();
    let value = 5;
    print!("Closure -> BoxConsumer: ");
    box_con.accept(&value);
    println!();

    // Closure -> RcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut rc_con = closure.into_rc();
    let value = 5;
    print!("Closure -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // Closure -> ArcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut arc_con = closure.into_arc();
    let value = 5;
    print!("Closure -> ArcConsumer: ");
    arc_con.accept(&value);
    println!();

    // BoxConsumer -> RcConsumer
    let box_con = BoxConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut rc_con = box_con.into_rc();
    let value = 5;
    print!("BoxConsumer -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // RcConsumer -> BoxConsumer
    let rc_con = RcConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut box_con = rc_con.into_box();
    let value = 5;
    print!("RcConsumer -> BoxConsumer: ");
    box_con.accept(&value);
    println!("\n");

    // ========================================================================
    // Example 14: Custom types
    // ========================================================================
    println!("Example 14: Custom types");
    println!("{}", "-".repeat(50));

    #[derive(Debug, Clone)]
    struct Point {
        x: i32,
        y: i32,
    }

    let mut analyzer = BoxConsumer::new(|p: &Point| {
        println!("Point coordinates: ({}, {})", p.x, p.y);
    })
    .and_then(|p: &Point| {
        let distance = ((p.x * p.x + p.y * p.y) as f64).sqrt();
        println!("Distance from origin: {:.2}", distance);
    })
    .and_then(|p: &Point| {
        let quadrant = match (p.x >= 0, p.y >= 0) {
            (true, true) => "First quadrant",
            (false, true) => "Second quadrant",
            (false, false) => "Third quadrant",
            (true, false) => "Fourth quadrant",
        };
        println!("Quadrant: {}", quadrant);
    });

    let point = Point { x: 3, y: 4 };
    println!("Analyzing point: {:?}", point);
    analyzer.accept(&point);
    println!("Original point: {:?} (not modified)\n", point);

    // ========================================================================
    // Example 15: Data collection and statistics
    // ========================================================================
    println!("Example 15: Data collection and statistics");
    println!("{}", "-".repeat(50));

    let sum = Arc::new(Mutex::new(0));
    let count = Arc::new(Mutex::new(0));
    let sum_clone = sum.clone();
    let count_clone = count.clone();

    let mut collector = BoxConsumer::new(move |x: &i32| {
        *sum_clone.lock().unwrap() += *x;
        *count_clone.lock().unwrap() += 1;
    });

    let numbers = vec![10, 20, 30, 40, 50];
    println!("Numbers: {:?}", numbers);
    for num in &numbers {
        collector.accept(num);
    }

    let total = *sum.lock().unwrap();
    let cnt = *count.lock().unwrap();
    println!("Sum: {}", total);
    println!("Count: {}", cnt);
    println!("Average: {:.2}\n", total as f64 / cnt as f64);

    println!("=== All examples completed ===");
    println!("\nTip: For value modification functionality, please refer to mutator_demo.rs");
}

pub fn new_with_name<F>(name: impl Into<String>, f: F) -> Self

where F: FnMut(&T) + 'static,

Create a new named BoxConsumer

Type Parameters

• F - Closure type

Parameters

• name - Name of the consumer
• f - Closure to wrap

Return Value

Returns a new BoxConsumer<T> instance

Examples

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let mut consumer = BoxConsumer::new_with_name("my_consumer", move |x: &i32| {
    l.lock().unwrap().push(*x + 1);
});
assert_eq!(consumer.name(), Some("my_consumer"));
consumer.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![6]);

pub fn noop() -> Self

Create a no-op consumer

Returns a consumer that performs no operation.

Return Value

Returns a no-op consumer

Examples

use prism3_function::{Consumer, BoxConsumer};

let mut noop = BoxConsumer::<i32>::noop();
noop.accept(&42);
// Value unchanged

Examples found in repository

examples/consumer_demo.rs (line 100)

fn main() {
    println!("=== Consumer Examples ===\n");
    println!("Note: Consumer only reads values, does not modify the original value");
    println!("If you need to modify values, please refer to mutator_demo.rs\n");

    // ========================================================================
    // Example 1: BoxConsumer basic usage
    // ========================================================================
    println!("Example 1: BoxConsumer basic usage");
    println!("{}", "-".repeat(50));

    let mut consumer = BoxConsumer::new(|x: &i32| {
        println!("Read and calculate: {} * 2 = {}", x, x * 2);
    });
    let value = 5;
    println!("Value: {}", value);
    consumer.accept(&value);
    println!("Value remains: {} (not modified)\n", value);

    // ========================================================================
    // Example 2: BoxConsumer method chaining
    // ========================================================================
    println!("Example 2: BoxConsumer method chaining");
    println!("{}", "-".repeat(50));

    let results = Arc::new(Mutex::new(Vec::new()));
    let r1 = results.clone();
    let r2 = results.clone();
    let r3 = results.clone();

    let mut chained = BoxConsumer::new(move |x: &i32| {
        r1.lock().unwrap().push(*x * 2);
    })
    .and_then(move |x: &i32| {
        r2.lock().unwrap().push(*x + 10);
    })
    .and_then(move |x: &i32| {
        r3.lock().unwrap().push(*x);
        println!("Processing value: {}", x);
    });

    let value = 5;
    println!("Initial value: {}", value);
    chained.accept(&value);
    println!("Collected results: {:?}", *results.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 3: Closure extension methods
    // ========================================================================
    println!("Example 3: Direct use of extension methods on closures");
    println!("{}", "-".repeat(50));

    let result = Arc::new(Mutex::new(0));
    let r1 = result.clone();
    let r2 = result.clone();

    let mut closure_chain = (move |x: &i32| {
        *r1.lock().unwrap() = *x * 2;
    })
    .and_then(move |_x: &i32| {
        *r2.lock().unwrap() += 10;
    });

    let value = 5;
    println!("Initial value: {}", value);
    closure_chain.accept(&value);
    println!("Calculation result: {}", *result.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 4: BoxConsumer factory methods
    // ========================================================================
    println!("Example 4: BoxConsumer factory methods");
    println!("{}", "-".repeat(50));

    // noop
    println!("noop - does nothing:");
    let mut noop = BoxConsumer::<i32>::noop();
    let value = 42;
    noop.accept(&value);
    println!("Value: {}\n", value);

    // print
    print!("print - prints value: ");
    let mut print = BoxConsumer::new(|x: &i32| println!("{}", x));
    let value = 42;
    print.accept(&value);
    println!();

    // print with prefix
    let mut print_with = BoxConsumer::new(|x: &i32| println!("Value is: {}", x));
    let value = 42;
    print_with.accept(&value);
    println!();

    // ========================================================================
    // Example 5: Conditional Consumer
    // ========================================================================
    println!("Example 5: Conditional Consumer");
    println!("{}", "-".repeat(50));

    // when
    let mut check_positive =
        BoxConsumer::new(|x: &i32| println!("Positive: {}", x)).when(|x: &i32| *x > 0);

    let positive = 5;
    let negative = -5;
    print!("Check {}: ", positive);
    check_positive.accept(&positive);
    print!("Check {}: ", negative);
    check_positive.accept(&negative);
    println!("(negative numbers not printed)\n");

    // when().or_else()
    let mut categorize = BoxConsumer::new(|x: &i32| println!("Positive: {}", x))
        .when(|x: &i32| *x > 0)
        .or_else(|x: &i32| println!("Non-positive: {}", x));

    let positive = 10;
    let negative = -10;
    categorize.accept(&positive);
    categorize.accept(&negative);
    println!();

    // ========================================================================
    // Example 6: ArcConsumer - multi-threaded sharing
    // ========================================================================
    println!("Example 6: ArcConsumer - multi-threaded sharing");
    println!("{}", "-".repeat(50));

    let shared = ArcConsumer::new(|x: &i32| println!("Processing value: {}", x * 2));

    // Clone for another thread
    let shared_clone = shared.clone();
    let handle = thread::spawn(move || {
        let value = 5;
        let mut consumer = shared_clone;
        consumer.accept(&value);
        value
    });

    // Use in main thread
    let value = 3;
    let mut consumer = shared;
    consumer.accept(&value);

    let thread_result = handle.join().unwrap();
    println!("Thread result: {}\n", thread_result);

    // ========================================================================
    // Example 7: ArcConsumer composition (does not consume original consumer)
    // ========================================================================
    println!("Example 7: ArcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = ArcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = ArcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    // Composition does not consume original consumer
    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);

    // double and add_ten are still available
    let value3 = 10;
    let mut d = double;
    print!("Original double still available, processing 10: ");
    d.accept(&value3);
    println!();

    // ========================================================================
    // Example 8: RcConsumer - single-threaded sharing
    // ========================================================================
    println!("Example 8: RcConsumer - single-threaded sharing");
    println!("{}", "-".repeat(50));

    let rc_consumer = RcConsumer::new(|x: &i32| println!("Processing: {}", x * 2));

    // Clone multiple copies
    let clone1 = rc_consumer.clone();
    let clone2 = rc_consumer.clone();

    let value1 = 5;
    let mut c1 = clone1;
    print!("clone1 processing 5: ");
    c1.accept(&value1);

    let value2 = 3;
    let mut c2 = clone2;
    print!("clone2 processing 3: ");
    c2.accept(&value2);

    let value3 = 7;
    let mut c3 = rc_consumer;
    print!("Original processing 7: ");
    c3.accept(&value3);
    println!();

    // ========================================================================
    // Example 9: RcConsumer composition (borrowing &self)
    // ========================================================================
    println!("Example 9: RcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = RcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = RcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);
    println!();

    // ========================================================================
    // Example 10: Unified Consumer trait
    // ========================================================================
    println!("Example 10: Unified Consumer trait");
    println!("{}", "-".repeat(50));

    fn log_all<C: Consumer<i32>>(consumer: &mut C, values: &[i32]) {
        for value in values.iter() {
            consumer.accept(value);
        }
    }

    let values = vec![1, 2, 3, 4, 5];

    let mut box_con = BoxConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("BoxConsumer processing {:?}: ", values);
    log_all(&mut box_con, &values);
    println!();

    let mut arc_con = ArcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("ArcConsumer processing {:?}: ", values);
    log_all(&mut arc_con, &values);
    println!();

    let mut rc_con = RcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("RcConsumer processing {:?}: ", values);
    log_all(&mut rc_con, &values);
    println!();

    let mut closure = |x: &i32| print!("{} ", x * 2);
    print!("Closure processing {:?}: ", values);
    log_all(&mut closure, &values);
    println!("\n");

    // ========================================================================
    // Example 11: Data validation and logging
    // ========================================================================
    println!("Example 11: Data validation and logging");
    println!("{}", "-".repeat(50));

    let validator = BoxConsumer::new(|x: &i32| {
        let status = if *x >= 0 && *x <= 100 {
            "valid"
        } else {
            "out of range"
        };
        println!("Validate {}: {}", x, status);
    });

    let logger = BoxConsumer::new(|x: &i32| {
        println!("Log to file: value={}, square={}", x, x * x);
    });

    let mut pipeline = validator.and_then(logger);

    let test_values = vec![-50, 30, 200];
    for value in test_values {
        pipeline.accept(&value);
    }
    println!();

    // ========================================================================
    // Example 12: String analysis
    // ========================================================================
    println!("Example 12: String analysis");
    println!("{}", "-".repeat(50));

    let mut string_analyzer = BoxConsumer::new(|s: &String| {
        println!("Length: {}", s.len());
    })
    .and_then(|s: &String| {
        println!("Lowercase: {}", s.to_lowercase());
    })
    .and_then(|s: &String| {
        println!("Uppercase: {}", s.to_uppercase());
    })
    .and_then(|s: &String| {
        let word_count = s.split_whitespace().count();
        println!("Word count: {}", word_count);
    });

    let text = String::from("Hello World");
    println!("Analyzing text: \"{}\"", text);
    string_analyzer.accept(&text);
    println!("Original text: \"{}\" (not modified)\n", text);

    // ========================================================================
    // Example 13: Type conversion
    // ========================================================================
    println!("Example 13: Type conversion");
    println!("{}", "-".repeat(50));

    // Closure -> BoxConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut box_con = closure.into_box();
    let value = 5;
    print!("Closure -> BoxConsumer: ");
    box_con.accept(&value);
    println!();

    // Closure -> RcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut rc_con = closure.into_rc();
    let value = 5;
    print!("Closure -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // Closure -> ArcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut arc_con = closure.into_arc();
    let value = 5;
    print!("Closure -> ArcConsumer: ");
    arc_con.accept(&value);
    println!();

    // BoxConsumer -> RcConsumer
    let box_con = BoxConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut rc_con = box_con.into_rc();
    let value = 5;
    print!("BoxConsumer -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // RcConsumer -> BoxConsumer
    let rc_con = RcConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut box_con = rc_con.into_box();
    let value = 5;
    print!("RcConsumer -> BoxConsumer: ");
    box_con.accept(&value);
    println!("\n");

    // ========================================================================
    // Example 14: Custom types
    // ========================================================================
    println!("Example 14: Custom types");
    println!("{}", "-".repeat(50));

    #[derive(Debug, Clone)]
    struct Point {
        x: i32,
        y: i32,
    }

    let mut analyzer = BoxConsumer::new(|p: &Point| {
        println!("Point coordinates: ({}, {})", p.x, p.y);
    })
    .and_then(|p: &Point| {
        let distance = ((p.x * p.x + p.y * p.y) as f64).sqrt();
        println!("Distance from origin: {:.2}", distance);
    })
    .and_then(|p: &Point| {
        let quadrant = match (p.x >= 0, p.y >= 0) {
            (true, true) => "First quadrant",
            (false, true) => "Second quadrant",
            (false, false) => "Third quadrant",
            (true, false) => "Fourth quadrant",
        };
        println!("Quadrant: {}", quadrant);
    });

    let point = Point { x: 3, y: 4 };
    println!("Analyzing point: {:?}", point);
    analyzer.accept(&point);
    println!("Original point: {:?} (not modified)\n", point);

    // ========================================================================
    // Example 15: Data collection and statistics
    // ========================================================================
    println!("Example 15: Data collection and statistics");
    println!("{}", "-".repeat(50));

    let sum = Arc::new(Mutex::new(0));
    let count = Arc::new(Mutex::new(0));
    let sum_clone = sum.clone();
    let count_clone = count.clone();

    let mut collector = BoxConsumer::new(move |x: &i32| {
        *sum_clone.lock().unwrap() += *x;
        *count_clone.lock().unwrap() += 1;
    });

    let numbers = vec![10, 20, 30, 40, 50];
    println!("Numbers: {:?}", numbers);
    for num in &numbers {
        collector.accept(num);
    }

    let total = *sum.lock().unwrap();
    let cnt = *count.lock().unwrap();
    println!("Sum: {}", total);
    println!("Count: {}", cnt);
    println!("Average: {:.2}\n", total as f64 / cnt as f64);

    println!("=== All examples completed ===");
    println!("\nTip: For value modification functionality, please refer to mutator_demo.rs");
}

pub fn name(&self) -> Option<&str>

Get the consumer’s name

Return Value

Returns the consumer’s name, or None if not set

pub fn set_name(&mut self, name: impl Into<String>)

Set the consumer’s name

Parameters

• name - Name to set

pub fn and_then<C>(self, next: C) -> Self

where C: Consumer<T> + 'static,

Sequentially chain another consumer

Returns a new consumer that executes the current operation first, then the next operation. Consumes self.

Type Parameters

• C - Type of the next consumer

Parameters

• next - Consumer to execute after the current operation. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original consumer, clone it first (if it implements Clone). Can be:
  • A closure: |x: &T|
  • A BoxConsumer<T>
  • An RcConsumer<T>
  • An ArcConsumer<T>
  • Any type implementing Consumer<T>

Return Value

Returns a new combined BoxConsumer<T>

Examples

Direct value passing (ownership transfer)

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l1 = log.clone();
let l2 = log.clone();
let first = BoxConsumer::new(move |x: &i32| {
    l1.lock().unwrap().push(*x * 2);
});
let second = BoxConsumer::new(move |x: &i32| {
    l2.lock().unwrap().push(*x + 10);
});

// second is moved here
let mut chained = first.and_then(second);
chained.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![10, 15]);
// second.accept(&3); // Would not compile - moved

Preserving original with clone

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l1 = log.clone();
let l2 = log.clone();
let first = BoxConsumer::new(move |x: &i32| {
    l1.lock().unwrap().push(*x * 2);
});
let second = BoxConsumer::new(move |x: &i32| {
    l2.lock().unwrap().push(*x + 10);
});

// Clone to preserve original
let mut chained = first.and_then(second.clone());
chained.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![10, 15]);

// Original still usable
second.accept(&3);
assert_eq!(*log.lock().unwrap(), vec![10, 15, 13]);

Examples found in repository

examples/consumer_fn_usage.rs (lines 85-87)

fn main() {
    println!("=== Consumer into_fn/to_fn Usage Examples ===\n");

    // Example 1: Using BoxConsumer::into_fn to pass to standard library's map
    println!("1. BoxConsumer::into_fn used with Iterator::for_each");
    let log = Arc::new(Mutex::new(Vec::new()));
    let l = log.clone();
    let consumer = BoxConsumer::new(move |x: &i32| {
        l.lock().unwrap().push(*x * 2);
    });

    // Convert consumer to closure and pass to for_each
    [1, 2, 3, 4, 5].iter().for_each(consumer.into_fn());
    println!("   Result: {:?}\n", *log.lock().unwrap());

    // Example 2: Using ArcConsumer::to_fn can be used multiple times
    println!("2. ArcConsumer::to_fn can be used multiple times");
    let log2 = Arc::new(Mutex::new(Vec::new()));
    let l2 = log2.clone();
    let consumer2 = ArcConsumer::new(move |x: &i32| {
        l2.lock().unwrap().push(*x + 10);
    });

    // to_fn doesn't consume consumer, can be called multiple times
    [1, 2, 3].iter().for_each(consumer2.to_fn());
    println!("   First time: {:?}", *log2.lock().unwrap());

    [4, 5].iter().for_each(consumer2.to_fn());
    println!("   Second time: {:?}\n", *log2.lock().unwrap());

    // Example 3: Using RcConsumer::to_fn
    println!("3. RcConsumer::to_fn used for single-threaded scenarios");
    let log3 = Rc::new(RefCell::new(Vec::new()));
    let l3 = log3.clone();
    let consumer3 = RcConsumer::new(move |x: &i32| {
        l3.borrow_mut().push(*x * 3);
    });

    [1, 2, 3, 4].iter().for_each(consumer3.to_fn());
    println!("   Result: {:?}\n", *log3.borrow());

    // Example 4: Using in custom functions
    println!("4. Using in custom functions");
    fn process_items<F>(items: Vec<i32>, consumer: F)
    where
        F: FnMut(&i32),
    {
        items.iter().for_each(consumer);
    }

    let log4 = Arc::new(Mutex::new(Vec::new()));
    let l4 = log4.clone();
    let consumer4 = BoxConsumer::new(move |x: &i32| {
        l4.lock().unwrap().push(*x * 5);
    });

    // Use into_fn to convert Consumer to closure and pass to function
    process_items(vec![1, 2, 3], consumer4.into_fn());
    println!("   Result: {:?}\n", *log4.lock().unwrap());

    // Example 5: Using into_fn after chained operations
    println!("5. Using into_fn after chained operations");
    let log5 = Arc::new(Mutex::new(Vec::new()));
    let l5 = log5.clone();
    let l6 = log5.clone();

    let chained = BoxConsumer::new(move |x: &i32| {
        l5.lock().unwrap().push(format!("A: {}", x));
    })
    .and_then(move |x: &i32| {
        l6.lock().unwrap().push(format!("B: {}", x));
    });

    [1, 2].iter().for_each(chained.into_fn());
    println!("   Result: {:?}\n", *log5.lock().unwrap());

    println!("=== Demo Complete ===");
}

examples/consumer_demo.rs (lines 55-57)

fn main() {
    println!("=== Consumer Examples ===\n");
    println!("Note: Consumer only reads values, does not modify the original value");
    println!("If you need to modify values, please refer to mutator_demo.rs\n");

    // ========================================================================
    // Example 1: BoxConsumer basic usage
    // ========================================================================
    println!("Example 1: BoxConsumer basic usage");
    println!("{}", "-".repeat(50));

    let mut consumer = BoxConsumer::new(|x: &i32| {
        println!("Read and calculate: {} * 2 = {}", x, x * 2);
    });
    let value = 5;
    println!("Value: {}", value);
    consumer.accept(&value);
    println!("Value remains: {} (not modified)\n", value);

    // ========================================================================
    // Example 2: BoxConsumer method chaining
    // ========================================================================
    println!("Example 2: BoxConsumer method chaining");
    println!("{}", "-".repeat(50));

    let results = Arc::new(Mutex::new(Vec::new()));
    let r1 = results.clone();
    let r2 = results.clone();
    let r3 = results.clone();

    let mut chained = BoxConsumer::new(move |x: &i32| {
        r1.lock().unwrap().push(*x * 2);
    })
    .and_then(move |x: &i32| {
        r2.lock().unwrap().push(*x + 10);
    })
    .and_then(move |x: &i32| {
        r3.lock().unwrap().push(*x);
        println!("Processing value: {}", x);
    });

    let value = 5;
    println!("Initial value: {}", value);
    chained.accept(&value);
    println!("Collected results: {:?}", *results.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 3: Closure extension methods
    // ========================================================================
    println!("Example 3: Direct use of extension methods on closures");
    println!("{}", "-".repeat(50));

    let result = Arc::new(Mutex::new(0));
    let r1 = result.clone();
    let r2 = result.clone();

    let mut closure_chain = (move |x: &i32| {
        *r1.lock().unwrap() = *x * 2;
    })
    .and_then(move |_x: &i32| {
        *r2.lock().unwrap() += 10;
    });

    let value = 5;
    println!("Initial value: {}", value);
    closure_chain.accept(&value);
    println!("Calculation result: {}", *result.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 4: BoxConsumer factory methods
    // ========================================================================
    println!("Example 4: BoxConsumer factory methods");
    println!("{}", "-".repeat(50));

    // noop
    println!("noop - does nothing:");
    let mut noop = BoxConsumer::<i32>::noop();
    let value = 42;
    noop.accept(&value);
    println!("Value: {}\n", value);

    // print
    print!("print - prints value: ");
    let mut print = BoxConsumer::new(|x: &i32| println!("{}", x));
    let value = 42;
    print.accept(&value);
    println!();

    // print with prefix
    let mut print_with = BoxConsumer::new(|x: &i32| println!("Value is: {}", x));
    let value = 42;
    print_with.accept(&value);
    println!();

    // ========================================================================
    // Example 5: Conditional Consumer
    // ========================================================================
    println!("Example 5: Conditional Consumer");
    println!("{}", "-".repeat(50));

    // when
    let mut check_positive =
        BoxConsumer::new(|x: &i32| println!("Positive: {}", x)).when(|x: &i32| *x > 0);

    let positive = 5;
    let negative = -5;
    print!("Check {}: ", positive);
    check_positive.accept(&positive);
    print!("Check {}: ", negative);
    check_positive.accept(&negative);
    println!("(negative numbers not printed)\n");

    // when().or_else()
    let mut categorize = BoxConsumer::new(|x: &i32| println!("Positive: {}", x))
        .when(|x: &i32| *x > 0)
        .or_else(|x: &i32| println!("Non-positive: {}", x));

    let positive = 10;
    let negative = -10;
    categorize.accept(&positive);
    categorize.accept(&negative);
    println!();

    // ========================================================================
    // Example 6: ArcConsumer - multi-threaded sharing
    // ========================================================================
    println!("Example 6: ArcConsumer - multi-threaded sharing");
    println!("{}", "-".repeat(50));

    let shared = ArcConsumer::new(|x: &i32| println!("Processing value: {}", x * 2));

    // Clone for another thread
    let shared_clone = shared.clone();
    let handle = thread::spawn(move || {
        let value = 5;
        let mut consumer = shared_clone;
        consumer.accept(&value);
        value
    });

    // Use in main thread
    let value = 3;
    let mut consumer = shared;
    consumer.accept(&value);

    let thread_result = handle.join().unwrap();
    println!("Thread result: {}\n", thread_result);

    // ========================================================================
    // Example 7: ArcConsumer composition (does not consume original consumer)
    // ========================================================================
    println!("Example 7: ArcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = ArcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = ArcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    // Composition does not consume original consumer
    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);

    // double and add_ten are still available
    let value3 = 10;
    let mut d = double;
    print!("Original double still available, processing 10: ");
    d.accept(&value3);
    println!();

    // ========================================================================
    // Example 8: RcConsumer - single-threaded sharing
    // ========================================================================
    println!("Example 8: RcConsumer - single-threaded sharing");
    println!("{}", "-".repeat(50));

    let rc_consumer = RcConsumer::new(|x: &i32| println!("Processing: {}", x * 2));

    // Clone multiple copies
    let clone1 = rc_consumer.clone();
    let clone2 = rc_consumer.clone();

    let value1 = 5;
    let mut c1 = clone1;
    print!("clone1 processing 5: ");
    c1.accept(&value1);

    let value2 = 3;
    let mut c2 = clone2;
    print!("clone2 processing 3: ");
    c2.accept(&value2);

    let value3 = 7;
    let mut c3 = rc_consumer;
    print!("Original processing 7: ");
    c3.accept(&value3);
    println!();

    // ========================================================================
    // Example 9: RcConsumer composition (borrowing &self)
    // ========================================================================
    println!("Example 9: RcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = RcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = RcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);
    println!();

    // ========================================================================
    // Example 10: Unified Consumer trait
    // ========================================================================
    println!("Example 10: Unified Consumer trait");
    println!("{}", "-".repeat(50));

    fn log_all<C: Consumer<i32>>(consumer: &mut C, values: &[i32]) {
        for value in values.iter() {
            consumer.accept(value);
        }
    }

    let values = vec![1, 2, 3, 4, 5];

    let mut box_con = BoxConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("BoxConsumer processing {:?}: ", values);
    log_all(&mut box_con, &values);
    println!();

    let mut arc_con = ArcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("ArcConsumer processing {:?}: ", values);
    log_all(&mut arc_con, &values);
    println!();

    let mut rc_con = RcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("RcConsumer processing {:?}: ", values);
    log_all(&mut rc_con, &values);
    println!();

    let mut closure = |x: &i32| print!("{} ", x * 2);
    print!("Closure processing {:?}: ", values);
    log_all(&mut closure, &values);
    println!("\n");

    // ========================================================================
    // Example 11: Data validation and logging
    // ========================================================================
    println!("Example 11: Data validation and logging");
    println!("{}", "-".repeat(50));

    let validator = BoxConsumer::new(|x: &i32| {
        let status = if *x >= 0 && *x <= 100 {
            "valid"
        } else {
            "out of range"
        };
        println!("Validate {}: {}", x, status);
    });

    let logger = BoxConsumer::new(|x: &i32| {
        println!("Log to file: value={}, square={}", x, x * x);
    });

    let mut pipeline = validator.and_then(logger);

    let test_values = vec![-50, 30, 200];
    for value in test_values {
        pipeline.accept(&value);
    }
    println!();

    // ========================================================================
    // Example 12: String analysis
    // ========================================================================
    println!("Example 12: String analysis");
    println!("{}", "-".repeat(50));

    let mut string_analyzer = BoxConsumer::new(|s: &String| {
        println!("Length: {}", s.len());
    })
    .and_then(|s: &String| {
        println!("Lowercase: {}", s.to_lowercase());
    })
    .and_then(|s: &String| {
        println!("Uppercase: {}", s.to_uppercase());
    })
    .and_then(|s: &String| {
        let word_count = s.split_whitespace().count();
        println!("Word count: {}", word_count);
    });

    let text = String::from("Hello World");
    println!("Analyzing text: \"{}\"", text);
    string_analyzer.accept(&text);
    println!("Original text: \"{}\" (not modified)\n", text);

    // ========================================================================
    // Example 13: Type conversion
    // ========================================================================
    println!("Example 13: Type conversion");
    println!("{}", "-".repeat(50));

    // Closure -> BoxConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut box_con = closure.into_box();
    let value = 5;
    print!("Closure -> BoxConsumer: ");
    box_con.accept(&value);
    println!();

    // Closure -> RcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut rc_con = closure.into_rc();
    let value = 5;
    print!("Closure -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // Closure -> ArcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut arc_con = closure.into_arc();
    let value = 5;
    print!("Closure -> ArcConsumer: ");
    arc_con.accept(&value);
    println!();

    // BoxConsumer -> RcConsumer
    let box_con = BoxConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut rc_con = box_con.into_rc();
    let value = 5;
    print!("BoxConsumer -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // RcConsumer -> BoxConsumer
    let rc_con = RcConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut box_con = rc_con.into_box();
    let value = 5;
    print!("RcConsumer -> BoxConsumer: ");
    box_con.accept(&value);
    println!("\n");

    // ========================================================================
    // Example 14: Custom types
    // ========================================================================
    println!("Example 14: Custom types");
    println!("{}", "-".repeat(50));

    #[derive(Debug, Clone)]
    struct Point {
        x: i32,
        y: i32,
    }

    let mut analyzer = BoxConsumer::new(|p: &Point| {
        println!("Point coordinates: ({}, {})", p.x, p.y);
    })
    .and_then(|p: &Point| {
        let distance = ((p.x * p.x + p.y * p.y) as f64).sqrt();
        println!("Distance from origin: {:.2}", distance);
    })
    .and_then(|p: &Point| {
        let quadrant = match (p.x >= 0, p.y >= 0) {
            (true, true) => "First quadrant",
            (false, true) => "Second quadrant",
            (false, false) => "Third quadrant",
            (true, false) => "Fourth quadrant",
        };
        println!("Quadrant: {}", quadrant);
    });

    let point = Point { x: 3, y: 4 };
    println!("Analyzing point: {:?}", point);
    analyzer.accept(&point);
    println!("Original point: {:?} (not modified)\n", point);

    // ========================================================================
    // Example 15: Data collection and statistics
    // ========================================================================
    println!("Example 15: Data collection and statistics");
    println!("{}", "-".repeat(50));

    let sum = Arc::new(Mutex::new(0));
    let count = Arc::new(Mutex::new(0));
    let sum_clone = sum.clone();
    let count_clone = count.clone();

    let mut collector = BoxConsumer::new(move |x: &i32| {
        *sum_clone.lock().unwrap() += *x;
        *count_clone.lock().unwrap() += 1;
    });

    let numbers = vec![10, 20, 30, 40, 50];
    println!("Numbers: {:?}", numbers);
    for num in &numbers {
        collector.accept(num);
    }

    let total = *sum.lock().unwrap();
    let cnt = *count.lock().unwrap();
    println!("Sum: {}", total);
    println!("Count: {}", cnt);
    println!("Average: {:.2}\n", total as f64 / cnt as f64);

    println!("=== All examples completed ===");
    println!("\nTip: For value modification functionality, please refer to mutator_demo.rs");
}

pub fn when<P>(self, predicate: P) -> BoxConditionalConsumer<T>

where P: Predicate<T> + 'static,

Creates a conditional consumer

Returns a consumer that only executes when a predicate is satisfied.

Parameters

• predicate - The condition to check. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Can be:
  • A closure: |x: &T| -> bool
  • A function pointer: fn(&T) -> bool
  • A BoxPredicate<T>
  • An RcPredicate<T>
  • An ArcPredicate<T>
  • Any type implementing Predicate<T>

Return Value

Returns BoxConditionalConsumer<T>

Examples

Using a closure

use prism3_function::{Consumer, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});
let mut conditional = consumer.when(|x: &i32| *x > 0);

conditional.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

conditional.accept(&-5);
assert_eq!(*log.lock().unwrap(), vec![5]); // Unchanged

Preserving predicate with clone

use prism3_function::{Consumer, BoxConsumer};
use prism3_function::predicate::{Predicate, RcPredicate};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let is_positive = RcPredicate::new(|x: &i32| *x > 0);
let consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});

// Clone to preserve original predicate
let mut conditional = consumer.when(is_positive.clone());

conditional.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

// Original predicate still usable
assert!(is_positive.test(&3));

Examples found in repository

examples/consumer_demo.rs (line 126)

fn main() {
    println!("=== Consumer Examples ===\n");
    println!("Note: Consumer only reads values, does not modify the original value");
    println!("If you need to modify values, please refer to mutator_demo.rs\n");

    // ========================================================================
    // Example 1: BoxConsumer basic usage
    // ========================================================================
    println!("Example 1: BoxConsumer basic usage");
    println!("{}", "-".repeat(50));

    let mut consumer = BoxConsumer::new(|x: &i32| {
        println!("Read and calculate: {} * 2 = {}", x, x * 2);
    });
    let value = 5;
    println!("Value: {}", value);
    consumer.accept(&value);
    println!("Value remains: {} (not modified)\n", value);

    // ========================================================================
    // Example 2: BoxConsumer method chaining
    // ========================================================================
    println!("Example 2: BoxConsumer method chaining");
    println!("{}", "-".repeat(50));

    let results = Arc::new(Mutex::new(Vec::new()));
    let r1 = results.clone();
    let r2 = results.clone();
    let r3 = results.clone();

    let mut chained = BoxConsumer::new(move |x: &i32| {
        r1.lock().unwrap().push(*x * 2);
    })
    .and_then(move |x: &i32| {
        r2.lock().unwrap().push(*x + 10);
    })
    .and_then(move |x: &i32| {
        r3.lock().unwrap().push(*x);
        println!("Processing value: {}", x);
    });

    let value = 5;
    println!("Initial value: {}", value);
    chained.accept(&value);
    println!("Collected results: {:?}", *results.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 3: Closure extension methods
    // ========================================================================
    println!("Example 3: Direct use of extension methods on closures");
    println!("{}", "-".repeat(50));

    let result = Arc::new(Mutex::new(0));
    let r1 = result.clone();
    let r2 = result.clone();

    let mut closure_chain = (move |x: &i32| {
        *r1.lock().unwrap() = *x * 2;
    })
    .and_then(move |_x: &i32| {
        *r2.lock().unwrap() += 10;
    });

    let value = 5;
    println!("Initial value: {}", value);
    closure_chain.accept(&value);
    println!("Calculation result: {}", *result.lock().unwrap());
    println!("Original value: {} (not modified)\n", value);

    // ========================================================================
    // Example 4: BoxConsumer factory methods
    // ========================================================================
    println!("Example 4: BoxConsumer factory methods");
    println!("{}", "-".repeat(50));

    // noop
    println!("noop - does nothing:");
    let mut noop = BoxConsumer::<i32>::noop();
    let value = 42;
    noop.accept(&value);
    println!("Value: {}\n", value);

    // print
    print!("print - prints value: ");
    let mut print = BoxConsumer::new(|x: &i32| println!("{}", x));
    let value = 42;
    print.accept(&value);
    println!();

    // print with prefix
    let mut print_with = BoxConsumer::new(|x: &i32| println!("Value is: {}", x));
    let value = 42;
    print_with.accept(&value);
    println!();

    // ========================================================================
    // Example 5: Conditional Consumer
    // ========================================================================
    println!("Example 5: Conditional Consumer");
    println!("{}", "-".repeat(50));

    // when
    let mut check_positive =
        BoxConsumer::new(|x: &i32| println!("Positive: {}", x)).when(|x: &i32| *x > 0);

    let positive = 5;
    let negative = -5;
    print!("Check {}: ", positive);
    check_positive.accept(&positive);
    print!("Check {}: ", negative);
    check_positive.accept(&negative);
    println!("(negative numbers not printed)\n");

    // when().or_else()
    let mut categorize = BoxConsumer::new(|x: &i32| println!("Positive: {}", x))
        .when(|x: &i32| *x > 0)
        .or_else(|x: &i32| println!("Non-positive: {}", x));

    let positive = 10;
    let negative = -10;
    categorize.accept(&positive);
    categorize.accept(&negative);
    println!();

    // ========================================================================
    // Example 6: ArcConsumer - multi-threaded sharing
    // ========================================================================
    println!("Example 6: ArcConsumer - multi-threaded sharing");
    println!("{}", "-".repeat(50));

    let shared = ArcConsumer::new(|x: &i32| println!("Processing value: {}", x * 2));

    // Clone for another thread
    let shared_clone = shared.clone();
    let handle = thread::spawn(move || {
        let value = 5;
        let mut consumer = shared_clone;
        consumer.accept(&value);
        value
    });

    // Use in main thread
    let value = 3;
    let mut consumer = shared;
    consumer.accept(&value);

    let thread_result = handle.join().unwrap();
    println!("Thread result: {}\n", thread_result);

    // ========================================================================
    // Example 7: ArcConsumer composition (does not consume original consumer)
    // ========================================================================
    println!("Example 7: ArcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = ArcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = ArcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    // Composition does not consume original consumer
    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);

    // double and add_ten are still available
    let value3 = 10;
    let mut d = double;
    print!("Original double still available, processing 10: ");
    d.accept(&value3);
    println!();

    // ========================================================================
    // Example 8: RcConsumer - single-threaded sharing
    // ========================================================================
    println!("Example 8: RcConsumer - single-threaded sharing");
    println!("{}", "-".repeat(50));

    let rc_consumer = RcConsumer::new(|x: &i32| println!("Processing: {}", x * 2));

    // Clone multiple copies
    let clone1 = rc_consumer.clone();
    let clone2 = rc_consumer.clone();

    let value1 = 5;
    let mut c1 = clone1;
    print!("clone1 processing 5: ");
    c1.accept(&value1);

    let value2 = 3;
    let mut c2 = clone2;
    print!("clone2 processing 3: ");
    c2.accept(&value2);

    let value3 = 7;
    let mut c3 = rc_consumer;
    print!("Original processing 7: ");
    c3.accept(&value3);
    println!();

    // ========================================================================
    // Example 9: RcConsumer composition (borrowing &self)
    // ========================================================================
    println!("Example 9: RcConsumer composition (borrowing &self)");
    println!("{}", "-".repeat(50));

    let double = RcConsumer::new(|x: &i32| println!("double: {}", x * 2));
    let add_ten = RcConsumer::new(|x: &i32| println!("add_ten: {}", x + 10));

    let pipeline1 = double.and_then(&add_ten);
    let pipeline2 = add_ten.and_then(&double);

    let value1 = 5;
    let mut p1 = pipeline1;
    print!("pipeline1 processing 5: ");
    p1.accept(&value1);

    let value2 = 5;
    let mut p2 = pipeline2;
    print!("pipeline2 processing 5: ");
    p2.accept(&value2);
    println!();

    // ========================================================================
    // Example 10: Unified Consumer trait
    // ========================================================================
    println!("Example 10: Unified Consumer trait");
    println!("{}", "-".repeat(50));

    fn log_all<C: Consumer<i32>>(consumer: &mut C, values: &[i32]) {
        for value in values.iter() {
            consumer.accept(value);
        }
    }

    let values = vec![1, 2, 3, 4, 5];

    let mut box_con = BoxConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("BoxConsumer processing {:?}: ", values);
    log_all(&mut box_con, &values);
    println!();

    let mut arc_con = ArcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("ArcConsumer processing {:?}: ", values);
    log_all(&mut arc_con, &values);
    println!();

    let mut rc_con = RcConsumer::new(|x: &i32| print!("{} ", x * 2));
    print!("RcConsumer processing {:?}: ", values);
    log_all(&mut rc_con, &values);
    println!();

    let mut closure = |x: &i32| print!("{} ", x * 2);
    print!("Closure processing {:?}: ", values);
    log_all(&mut closure, &values);
    println!("\n");

    // ========================================================================
    // Example 11: Data validation and logging
    // ========================================================================
    println!("Example 11: Data validation and logging");
    println!("{}", "-".repeat(50));

    let validator = BoxConsumer::new(|x: &i32| {
        let status = if *x >= 0 && *x <= 100 {
            "valid"
        } else {
            "out of range"
        };
        println!("Validate {}: {}", x, status);
    });

    let logger = BoxConsumer::new(|x: &i32| {
        println!("Log to file: value={}, square={}", x, x * x);
    });

    let mut pipeline = validator.and_then(logger);

    let test_values = vec![-50, 30, 200];
    for value in test_values {
        pipeline.accept(&value);
    }
    println!();

    // ========================================================================
    // Example 12: String analysis
    // ========================================================================
    println!("Example 12: String analysis");
    println!("{}", "-".repeat(50));

    let mut string_analyzer = BoxConsumer::new(|s: &String| {
        println!("Length: {}", s.len());
    })
    .and_then(|s: &String| {
        println!("Lowercase: {}", s.to_lowercase());
    })
    .and_then(|s: &String| {
        println!("Uppercase: {}", s.to_uppercase());
    })
    .and_then(|s: &String| {
        let word_count = s.split_whitespace().count();
        println!("Word count: {}", word_count);
    });

    let text = String::from("Hello World");
    println!("Analyzing text: \"{}\"", text);
    string_analyzer.accept(&text);
    println!("Original text: \"{}\" (not modified)\n", text);

    // ========================================================================
    // Example 13: Type conversion
    // ========================================================================
    println!("Example 13: Type conversion");
    println!("{}", "-".repeat(50));

    // Closure -> BoxConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut box_con = closure.into_box();
    let value = 5;
    print!("Closure -> BoxConsumer: ");
    box_con.accept(&value);
    println!();

    // Closure -> RcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut rc_con = closure.into_rc();
    let value = 5;
    print!("Closure -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // Closure -> ArcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let mut arc_con = closure.into_arc();
    let value = 5;
    print!("Closure -> ArcConsumer: ");
    arc_con.accept(&value);
    println!();

    // BoxConsumer -> RcConsumer
    let box_con = BoxConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut rc_con = box_con.into_rc();
    let value = 5;
    print!("BoxConsumer -> RcConsumer: ");
    rc_con.accept(&value);
    println!();

    // RcConsumer -> BoxConsumer
    let rc_con = RcConsumer::new(|x: &i32| print!("Processing: {} ", x * 2));
    let mut box_con = rc_con.into_box();
    let value = 5;
    print!("RcConsumer -> BoxConsumer: ");
    box_con.accept(&value);
    println!("\n");

    // ========================================================================
    // Example 14: Custom types
    // ========================================================================
    println!("Example 14: Custom types");
    println!("{}", "-".repeat(50));

    #[derive(Debug, Clone)]
    struct Point {
        x: i32,
        y: i32,
    }

    let mut analyzer = BoxConsumer::new(|p: &Point| {
        println!("Point coordinates: ({}, {})", p.x, p.y);
    })
    .and_then(|p: &Point| {
        let distance = ((p.x * p.x + p.y * p.y) as f64).sqrt();
        println!("Distance from origin: {:.2}", distance);
    })
    .and_then(|p: &Point| {
        let quadrant = match (p.x >= 0, p.y >= 0) {
            (true, true) => "First quadrant",
            (false, true) => "Second quadrant",
            (false, false) => "Third quadrant",
            (true, false) => "Fourth quadrant",
        };
        println!("Quadrant: {}", quadrant);
    });

    let point = Point { x: 3, y: 4 };
    println!("Analyzing point: {:?}", point);
    analyzer.accept(&point);
    println!("Original point: {:?} (not modified)\n", point);

    // ========================================================================
    // Example 15: Data collection and statistics
    // ========================================================================
    println!("Example 15: Data collection and statistics");
    println!("{}", "-".repeat(50));

    let sum = Arc::new(Mutex::new(0));
    let count = Arc::new(Mutex::new(0));
    let sum_clone = sum.clone();
    let count_clone = count.clone();

    let mut collector = BoxConsumer::new(move |x: &i32| {
        *sum_clone.lock().unwrap() += *x;
        *count_clone.lock().unwrap() += 1;
    });

    let numbers = vec![10, 20, 30, 40, 50];
    println!("Numbers: {:?}", numbers);
    for num in &numbers {
        collector.accept(num);
    }

    let total = *sum.lock().unwrap();
    let cnt = *count.lock().unwrap();
    println!("Sum: {}", total);
    println!("Count: {}", cnt);
    println!("Average: {:.2}\n", total as f64 / cnt as f64);

    println!("=== All examples completed ===");
    println!("\nTip: For value modification functionality, please refer to mutator_demo.rs");
}

Trait Implementations

impl<T> Consumer<T> for BoxConsumer<T>

fn accept(&mut self, value: &T)

Execute consumption operation

fn into_box(self) -> BoxConsumer<T>

where T: 'static,

Convert to BoxConsumer

fn into_rc(self) -> RcConsumer<T>

where T: 'static,

Convert to RcConsumer

fn into_fn(self) -> impl FnMut(&T)

where T: 'static,

Convert to closure

fn into_arc(self) -> ArcConsumer<T>

where Self: Sized + Send + 'static, T: Send + 'static,

Convert to ArcConsumer

impl<T> ConsumerOnce<T> for BoxConsumer<T>

fn accept_once(self, value: &T)

Execute one-time consumption operation

Executes the consumer operation once and consumes self. This method provides a bridge between the reusable Consumer interface and the one-time ConsumerOnce interface.

Parameters

• value - Reference to the value to be consumed

Examples

use prism3_function::{Consumer, ConsumerOnce, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});
consumer.accept_once(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

fn into_box_once(self) -> BoxConsumerOnce<T>

where T: 'static,

Convert to BoxConsumerOnce

⚠️ Consumes self: The original consumer will be unavailable after calling this method.

Converts the current consumer to BoxConsumerOnce<T> by wrapping the consumer’s accept method in a FnOnce closure.

Return Value

Returns the wrapped BoxConsumerOnce<T>

Examples

use prism3_function::{Consumer, ConsumerOnce, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});
let box_consumer_once = consumer.into_box_once();
box_consumer_once.accept_once(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

fn into_fn_once(self) -> impl FnOnce(&T)

where T: 'static,

Convert to closure

⚠️ Consumes self: The original consumer will be unavailable after calling this method.

Converts the consumer to a closure that can be used directly in places where the standard library requires FnOnce.

Return Value

Returns a closure implementing FnOnce(&T)

Examples

use prism3_function::{Consumer, ConsumerOnce, BoxConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let consumer = BoxConsumer::new(move |x: &i32| {
    l.lock().unwrap().push(*x);
});
let func = consumer.into_fn_once();
func(&5);
assert_eq!(*log.lock().unwrap(), vec![5]);

impl<T> Debug for BoxConsumer<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Display for BoxConsumer<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.