Struct BoxConditionalStatefulConsumer 

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

BoxConditionalStatefulConsumer struct

A conditional consumer that only executes when a predicate is satisfied. Uses BoxStatefulConsumer and BoxPredicate for single ownership semantics.

This type is typically created by calling BoxStatefulConsumer::when() and is designed to work with the or_else() method to create if-then-else logic.

Features

• Single Ownership: Not cloneable, consumes self on use
• Conditional Execution: Only consumes when predicate returns true
• Chainable: Can add or_else branch to create if-then-else logic
• Implements Consumer: Can be used anywhere a Consumer is expected

Examples

Basic Conditional Execution

use qubit_function::{Consumer, StatefulConsumer, BoxStatefulConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l = log.clone();
let consumer = BoxStatefulConsumer::new(move |x: &i32| {
    l.lock().expect("mutex should not be poisoned").push(*x);
});
let mut conditional = consumer.when(|x: &i32| *x > 0);

conditional.accept(&5);
assert_eq!(*log.lock().expect("mutex should not be poisoned"), vec![5]); // Executed

conditional.accept(&-5);
assert_eq!(*log.lock().expect("mutex should not be poisoned"), vec![5]); // Not executed

With or_else Branch

use qubit_function::{Consumer, StatefulConsumer, BoxStatefulConsumer};
use std::sync::{Arc, Mutex};

let log = Arc::new(Mutex::new(Vec::new()));
let l1 = log.clone();
let l2 = log.clone();
let mut consumer = BoxStatefulConsumer::new(move |x: &i32| {
    l1.lock().expect("mutex should not be poisoned").push(*x);
})
.when(|x: &i32| *x > 0)
.or_else(move |x: &i32| {
    l2.lock().expect("mutex should not be poisoned").push(-*x);
});

consumer.accept(&5);
assert_eq!(*log.lock().expect("mutex should not be poisoned"), vec![5]); // when branch executed

consumer.accept(&-5);
assert_eq!(*log.lock().expect("mutex should not be poisoned"), vec![5, 5]); // or_else branch executed

Implementations

impl<T> BoxConditionalStatefulConsumer<T>

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

where T: 'static, C: StatefulConsumer<T> + 'static,

Chains another consumer in sequence

Combines the current conditional consumer with another consumer into a new consumer that implements the following semantics:

When the returned consumer is called with an argument:

1. First, it checks the predicate of this conditional consumer
2. If the predicate is satisfied, it executes the internal consumer of this conditional consumer
3. Then, regardless of whether the predicate was satisfied, it unconditionally executes the next consumer

In other words, this creates a consumer that conditionally executes the first action (based on the predicate), and then always executes the second action.

Parameters

• next - The next consumer to execute (always executed)

Returns

Returns a new combined consumer

Examples

use std::sync::atomic::{AtomicI32, Ordering};
use std::sync::Arc;
use qubit_function::BoxConsumer;
use qubit_function::Consumer;

let result = Arc::new(AtomicI32::new(0));
let result1 = result.clone();
let result2 = result.clone();

let consumer1 = BoxConsumer::new(move |x: &i32| {
    result1.fetch_add(*x, Ordering::SeqCst);
});

let consumer2 = BoxConsumer::new(move |x: &i32| {
    result2.fetch_add(2 * (*x), Ordering::SeqCst);
});
let result3 = result.clone();

let conditional = consumer1.when(|x: &i32| *x > 0);
let chained = conditional.and_then(consumer2);

chained.accept(&5);  // result = 5 + (2*5) = 15
result3.store(0, Ordering::SeqCst);  // reset
chained.accept(&-5); // result = 0 + (2*-5) = -10 (not -15!)

pub fn or_else<C>(self, else_consumer: C) -> BoxStatefulConsumer<T>

where T: 'static, C: StatefulConsumer<T> + 'static,

Adds an else branch

Executes the original consumer when the condition is satisfied, otherwise executes else_consumer.

Parameters

• else_consumer - The consumer for the else branch

Returns

Returns a new consumer with if-then-else logic

Examples found in repository

examples/consumers/consumer_demo.rs (line 156)

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 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 chained = BoxConsumer::new(move |x: &i32| {
        r1.lock().expect("mutex should not be poisoned").push(*x * 2);
    })
    .and_then(move |x: &i32| {
        r2.lock().expect("mutex should not be poisoned").push(*x + 10);
    })
    .and_then(move |x: &i32| {
        r3.lock().expect("mutex should not be poisoned").push(*x);
        println!("Processing value: {}", x);
    });

    let value = 5;
    println!("Initial value: {}", value);
    chained.accept(&value);
    println!(
        "Collected results: {:?}",
        *results.lock().expect("mutex should not be poisoned")
    );
    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 closure_chain = (move |x: &i32| {
        *r1.lock().expect("mutex should not be poisoned") = *x * 2;
    })
    .and_then(move |_x: &i32| {
        *r2.lock().expect("mutex should not be poisoned") += 10;
    });

    let value = 5;
    println!("Initial value: {}", value);
    closure_chain.accept(&value);
    println!(
        "Calculation result: {}",
        *result.lock().expect("mutex should not be poisoned")
    );
    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 noop = BoxConsumer::<i32>::noop();
    let value = 42;
    noop.accept(&value);
    println!("Value: {}\n", value);

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

    // print with prefix
    let 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 = BoxStatefulConsumer::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 = BoxStatefulConsumer::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 consumer = shared_clone;
        consumer.accept(&value);
        value
    });

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

    let thread_result = handle.join().expect("thread should not panic");
    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.clone());
    let pipeline2 = add_ten.and_then(double.clone());

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

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

    // double and add_ten are still available
    let value3 = 10;
    let 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 c1 = clone1;
    print!("clone1 processing 5: ");
    c1.accept(&value1);

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

    let value3 = 7;
    let 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.clone());
    let pipeline2 = add_ten.and_then(double.clone());

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

    let value2 = 5;
    let 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 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 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 box_con = Consumer::into_box(closure);
    let value = 5;
    print!("Closure -> BoxConsumer: ");
    box_con.accept(&value);
    println!();

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

    // Closure -> ArcConsumer
    let closure = |x: &i32| print!("Processing: {} ", x * 2);
    let arc_con = Consumer::into_arc(closure);
    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 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 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 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 collector = BoxConsumer::new(move |x: &i32| {
        *sum_clone.lock().expect("mutex should not be poisoned") += *x;
        *count_clone.lock().expect("mutex should not be poisoned") += 1;
    });

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

    let total = *sum.lock().expect("mutex should not be poisoned");
    let cnt = *count.lock().expect("mutex should not be poisoned");
    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> Debug for BoxConditionalStatefulConsumer<T>

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

Formats the value using the given formatter.

impl<T> Display for BoxConditionalStatefulConsumer<T>

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

Formats the value using the given formatter.

impl<T> StatefulConsumer<T> for BoxConditionalStatefulConsumer<T>

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

Execute consumption operation

fn into_box(self) -> BoxStatefulConsumer<T>

where Self: 'static,

Convert to BoxStatefulConsumer

fn into_rc(self) -> RcStatefulConsumer<T>

where Self: 'static,

Convert to RcStatefulConsumer

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

Convert to closure

fn into_arc(self) -> ArcStatefulConsumer<T>

where Self: Sized + Send + 'static,

Convert to ArcStatefulConsumer

fn into_once(self) -> BoxConsumerOnce<T>

where Self: Sized + 'static,

Convert to ConsumerOnce