Trait FnConsumerOps 

pub trait FnConsumerOps<T>: FnMut(&T) + Sized {
    // Provided method
    fn and_then<C>(self, next: C) -> BoxConsumer<T>
       where Self: 'static,
             C: Consumer<T> + 'static,
             T: 'static { ... }
}

Extension trait providing consumer composition methods for closures

Provides and_then and other composition methods for all closures implementing FnMut(&T), allowing direct method chaining on closures without explicit wrapper types.

Design Philosophy

This trait allows closures to be naturally composed using method syntax, similar to iterator combinators. Composition methods consume the closure and return BoxConsumer<T>, which can continue chaining.

Features

• Natural Syntax: Direct method chaining on closures
• Returns BoxConsumer: Composition results in BoxConsumer<T>, can continue chaining
• Zero Cost: No overhead when composing closures
• Automatic Implementation: All FnMut(&T) closures automatically get these methods

Examples

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

let log = Arc::new(Mutex::new(Vec::new()));
let l1 = log.clone();
let l2 = log.clone();
let mut chained = (move |x: &i32| {
    l1.lock().unwrap().push(*x * 2);
}).and_then(move |x: &i32| {
    l2.lock().unwrap().push(*x + 10);
});
chained.accept(&5);
assert_eq!(*log.lock().unwrap(), vec![10, 15]);
// (5 * 2), (5 + 10)

Author

Hu Haixing

Provided Methods

fn and_then<C>(self, next: C) -> BoxConsumer<T>

where Self: 'static, C: Consumer<T> + 'static, T: 'static,

Sequentially chain another consumer

Returns a new consumer that executes the current operation first, then the next operation. Consumes the current closure and returns BoxConsumer<T>.

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 combined BoxConsumer<T>

Examples

Direct value passing (ownership transfer)

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

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

// second is moved here
let mut chained = (move |x: &i32| {
    l1.lock().unwrap().push(*x * 2);
}).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, FnConsumerOps, BoxConsumer};
use std::sync::{Arc, Mutex};

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

// Clone to preserve original
let mut chained = (move |x: &i32| {
    l1.lock().unwrap().push(*x * 2);
}).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_demo.rs (lines 82-84)

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");
}

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<T, F> FnConsumerOps<T> for F

where F: FnMut(&T),

Implement FnConsumerOps for all closure types