Struct RcStatefulTransformer 

pub struct RcStatefulTransformer<T, R> { /* private fields */ }

RcStatefulTransformer - single-threaded transformer wrapper

A single-threaded, clonable transformer wrapper optimized for scenarios that require sharing without thread-safety overhead.

Features

• Based on: Rc<RefCell<dyn FnMut(T) -> R>>
• Ownership: Shared ownership via reference counting (non-atomic)
• Reusability: Can be called multiple times (each call consumes its input)
• Thread Safety: Not thread-safe (no Send + Sync)
• Clonable: Cheap cloning via Rc::clone
• Statefulness: Can modify internal state between calls

Implementations

impl<T, R> RcStatefulTransformer<T, R>

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

where F: FnMut(T) -> R + 'static,

Creates a new transformer.

Wraps the provided closure in the appropriate smart pointer type for this transformer implementation.

Examples found in repository

examples/transformers/stateful_transformer_demo.rs (lines 80-83)

fn main() {
    println!("=== StatefulTransformer Demo ===\n");

    // 1. Basic BoxStatefulTransformer with state
    println!("1. BoxStatefulTransformer with stateful counter:");
    let mut counter = 0;
    let mut mapper = BoxStatefulTransformer::new(move |x: i32| {
        counter += 1;
        format!("Item #{}: {}", counter, x)
    });

    println!("  {}", mapper.apply(100)); // Item #1: 100
    println!("  {}", mapper.apply(200)); // Item #2: 200
    println!("  {}", mapper.apply(300)); // Item #3: 300

    // 2. Composing mappers with and_then
    println!("\n2. Composing mappers with and_then:");
    let mut counter1 = 0;
    let mapper1 = BoxStatefulTransformer::new(move |x: i32| {
        counter1 += 1;
        x + counter1
    });

    let mut counter2 = 0;
    let mapper2 = BoxStatefulTransformer::new(move |x: i32| {
        counter2 += 1;
        x * counter2
    });

    let mut composed = mapper1.and_then(mapper2);
    println!("  First call:  {}", composed.apply(10)); // (10 + 1) * 1 = 11
    println!("  Second call: {}", composed.apply(10)); // (10 + 2) * 2 = 24
    println!("  Third call:  {}", composed.apply(10)); // (10 + 3) * 3 = 39

    // 3. Conditional mapping with when/or_else
    println!("\n3. Conditional mapping:");
    let mut high_count = 0;
    let mut low_count = 0;

    let mut conditional = BoxStatefulTransformer::new(move |x: i32| {
        high_count += 1;
        format!("High[{}]: {} * 2 = {}", high_count, x, x * 2)
    })
    .when(|x: &i32| *x >= 10)
    .or_else(move |x| {
        low_count += 1;
        format!("Low[{}]: {} + 1 = {}", low_count, x, x + 1)
    });

    println!("  {}", conditional.apply(15)); // High[1]: 15 * 2 = 30
    println!("  {}", conditional.apply(5)); // Low[1]: 5 + 1 = 6
    println!("  {}", conditional.apply(20)); // High[2]: 20 * 2 = 40

    // 4. RcStatefulTransformer for cloneable mappers
    println!("\n4. RcStatefulTransformer (cloneable, single-threaded):");
    let mut counter = 0;
    let mapper = RcStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x + counter
    });

    let mut mapper1 = mapper.clone();
    let mut mapper2 = mapper.clone();

    println!("  mapper1: {}", mapper1.apply(10)); // 11
    println!("  mapper2: {}", mapper2.apply(10)); // 12
    println!("  mapper1: {}", mapper1.apply(10)); // 13

    // 5. ArcStatefulTransformer for thread-safe mappers
    println!("\n5. ArcStatefulTransformer (thread-safe):");
    let mut counter = 0;
    let mapper = ArcStatefulTransformer::new(move |x: i32| {
        counter += 1;
        format!("Result[{}]: {}", counter, x * 2)
    });

    let mut mapper_clone = mapper.clone();
    println!("  Original: {}", mapper_clone.apply(5)); // Result[1]: 10
    println!("  Clone:    {}", mapper_clone.apply(7)); // Result[2]: 14

    // 6. Using FnStatefulTransformerOps extension trait
    println!("\n6. Using FnStatefulTransformerOps extension trait:");
    let mut count = 0;
    let mut mapper = (move |x: i32| {
        count += 1;
        x + count
    })
    .and_then(|x| x * 2);

    println!("  {}", mapper.apply(10)); // (10 + 1) * 2 = 22
    println!("  {}", mapper.apply(10)); // (10 + 2) * 2 = 24

    // 7. Building a complex pipeline
    println!("\n7. Complex processing pipeline:");
    let mut step1_count = 0;
    let step1 = BoxStatefulTransformer::new(move |x: i32| {
        step1_count += 1;
        format!("Step1[{}]: {}", step1_count, x)
    });

    let mut step2_count = 0;
    let step2 = BoxStatefulTransformer::new(move |s: String| {
        step2_count += 1;
        format!("{} -> Step2[{}]", s, step2_count)
    });

    let mut step3_count = 0;
    let step3 = BoxStatefulTransformer::new(move |s: String| {
        step3_count += 1;
        format!("{} -> Step3[{}]", s, step3_count)
    });

    let mut pipeline = step1.and_then(step2).and_then(step3);

    println!("  {}", pipeline.apply(100));
    println!("  {}", pipeline.apply(200));

    // 7. TransformerOnce implementation - consuming transformers
    println!("\n7. TransformerOnce implementation - consuming StatefulTransformers:");

    // BoxStatefulTransformer can be consumed as TransformerOnce
    let mut counter = 0;
    let mut box_mapper = BoxStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x * counter
    });
    println!(
        "  BoxStatefulTransformer consumed once: {}",
        box_mapper.apply(10)
    ); // 10 * 1 = 10

    // RcStatefulTransformer can be consumed as TransformerOnce
    let mut counter = 0;
    let mut rc_mapper = RcStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x + counter
    });
    let rc_clone = rc_mapper.clone(); // Clone before consuming
    println!(
        "  RcStatefulTransformer consumed once: {}",
        rc_mapper.apply(10)
    ); // 10 + 1 = 11
    println!("  RcStatefulTransformer clone still works: {}", {
        let mut rc_clone_for_call = rc_clone.clone();
        rc_clone_for_call.apply(10)
    }); // 10 + 2 = 12

    // ArcStatefulTransformer can be consumed as TransformerOnce
    let mut counter = 0;
    let mut arc_mapper = ArcStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x * counter
    });
    let arc_clone = arc_mapper.clone(); // Clone before consuming
    println!(
        "  ArcStatefulTransformer consumed once: {}",
        arc_mapper.apply(10)
    ); // 10 * 1 = 10
    println!("  ArcStatefulTransformer clone still works: {}", {
        let mut arc_clone_for_call = arc_clone.clone();
        arc_clone_for_call.apply(10)
    }); // 10 * 2 = 20

    // 8. Converting to BoxTransformerOnce
    println!("\n8. Converting StatefulTransformers to BoxTransformerOnce:");

    let mut counter = 0;
    let mapper = BoxStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x * counter
    });
    let mut once_mapper = mapper.into_box();
    println!(
        "  BoxStatefulTransformer->BoxTransformerOnce: {}",
        once_mapper.apply(5)
    ); // 5 * 1 = 5

    // RcStatefulTransformer can use to_box() to preserve original
    let mut counter = 0;
    let rc_mapper = RcStatefulTransformer::new(move |x: i32| {
        counter += 1;
        x * counter
    });
    let mut once_mapper = rc_mapper.to_box();
    println!(
        "  RcStatefulTransformer->BoxTransformerOnce: {}",
        once_mapper.apply(5)
    ); // 5 * 1 = 5
    println!("  Original RcStatefulTransformer still works: {}", {
        let mut rc_original_for_call = rc_mapper.clone();
        rc_original_for_call.apply(5)
    }); // 5 * 2 = 10

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

pub fn new_with_name<F>(name: &str, f: F) -> Self

where F: FnMut(T) -> R + 'static,

Creates a new named transformer.

Wraps the provided closure and assigns it a name, which is useful for debugging and logging purposes.

pub fn new_with_optional_name<F>(f: F, name: Option<String>) -> Self

where F: FnMut(T) -> R + 'static,

Creates a new named transformer with an optional name.

Wraps the provided closure and assigns it an optional name.

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

Gets the name of this transformer.

Returns

Returns Some(&str) if a name was set, None otherwise.

pub fn set_name(&mut self, name: &str)

Sets the name of this transformer.

Parameters

• name - The name to set for this transformer

pub fn clear_name(&mut self)

Clears the name of this transformer.

pub fn identity() -> RcStatefulTransformer<T, T>

Creates an identity transformer.

Creates a transformer that returns the input value unchanged. Useful for default values or placeholder implementations.

Returns

Returns a new transformer instance that returns the input unchanged.

pub fn when<P>(&self, predicate: P) -> RcConditionalStatefulTransformer<T, R>

where T: 'static, R: 'static, P: Predicate<T> + 'static,

pub fn and_then<S, F>(&self, after: F) -> RcStatefulTransformer<T, S>

where T: 'static, R: 'static, S: 'static, F: StatefulTransformer<R, S> + 'static,

impl<T, R> RcStatefulTransformer<T, R>

pub fn constant(value: R) -> RcStatefulTransformer<T, R>

where R: Clone + 'static,

Creates a constant transformer

Examples

/// rust /// use qubit_function::{RcStatefulTransformer, StatefulTransformer}; /// /// let mut constant = RcStatefulTransformer::constant("hello"); /// assert_eq!(constant.apply(123), "hello"); ///

Trait Implementations

impl<T, R> Clone for RcStatefulTransformer<T, R>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, R> Debug for RcStatefulTransformer<T, R>

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

Formats the value using the given formatter.

impl<T, R> Display for RcStatefulTransformer<T, R>

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

Formats the value using the given formatter.

impl<T, R> StatefulTransformer<T, R> for RcStatefulTransformer<T, R>

fn apply(&mut self, input: T) -> R

Applies the transformation to the input value to produce an output value

fn into_box(self) -> BoxStatefulTransformer<T, R>

where Self: 'static,

Converts to BoxStatefulTransformer

fn into_rc(self) -> RcStatefulTransformer<T, R>

Converts to RcStatefulTransformer

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

Converts to a closure implementing FnMut(T) -> R

fn to_box(&self) -> BoxStatefulTransformer<T, R>

where Self: 'static,

Non-consuming conversion to BoxStatefulTransformer.

fn to_rc(&self) -> RcStatefulTransformer<T, R>

Non-consuming conversion to RcStatefulTransformer.

fn to_fn(&self) -> impl FnMut(T) -> R

Non-consuming conversion to a closure (FnMut(T) -> R).

fn into_once(self) -> BoxTransformerOnce<T, R>

where Self: 'static,

Converts to BoxTransformerOnce.

fn to_once(&self) -> BoxTransformerOnce<T, R>

where Self: 'static,

Creates a BoxTransformerOnce from a cloned transformer

fn into_arc(self) -> ArcStatefulTransformer<T, R>

where Self: Sized + Send + 'static,

Converts to ArcStatefulTransformer

fn into_mut_fn(self) -> impl FnMut(T) -> R

where Self: Sized + 'static,

Converts transformer to a mutable closure (FnMut) with an explicit method name.

fn to_arc(&self) -> ArcStatefulTransformer<T, R>

where Self: Sized + Clone + Send + 'static,

Non-consuming conversion to ArcStatefulTransformer (thread-safe).

fn to_mut_fn(&self) -> impl FnMut(T) -> R

where Self: Sized + Clone + 'static,

Non-consuming conversion to a mutable closure (FnMut) with an explicit method name.