Struct relm4::shared_state::Reducer

source ·
pub struct Reducer<Data: Reducible> { /* private fields */ }
Expand description

A type that allows you to share information across your application easily.

Reducers receive messages, update their state accordingly and notify their subscribers.

Unlike SharedState, this type doesn’t allow direct access to the internal data. Instead, it updates its state after receiving messages, similar to components. After the message is processed, all subscribers will be notified.

Example

use relm4::{Reducer, Reducible};

struct CounterReducer(u8);

enum CounterInput {
    Increment,
    Decrement,
}

impl Reducible for CounterReducer {
    type Input = CounterInput;

    fn init() -> Self {
        Self(0)
    }

    fn reduce(&mut self, input: Self::Input) -> bool {
        match input {
            CounterInput::Increment => {
                self.0 += 1;
            }
            CounterInput::Decrement =>  {
                self.0 -= 1;
            }
        }
        true
    }
}

// Create the reducer.
static REDUCER: Reducer<CounterReducer> = Reducer::new();

// Update the reducer.
REDUCER.emit(CounterInput::Increment);

// Create a channel and subscribe to changes.
let (sender, receiver) = relm4::channel();
REDUCER.subscribe(&sender, |data| data.0);

// Count up to 2.
REDUCER.emit(CounterInput::Increment);
assert_eq!(receiver.recv_sync().unwrap(), 2);

Implementations§

source§

impl<Data> Reducer<Data>where Data: Reducible + Send + 'static, Data::Input: Send,

source

pub const fn new() -> Self

Create a new Reducer variable.

The data will be initialized lazily on the first access.

source

pub fn subscribe<Msg, F>(&self, sender: &Sender<Msg>, f: F)where F: Fn(&Data) -> Msg + 'static + Send + Sync, Msg: Send + 'static,

Subscribe to a Reducer. Any subscriber will be notified with a message every time you modify the reducer (by calling Self::emit()).

source

pub fn subscribe_optional<Msg, F>(&self, sender: &Sender<Msg>, f: F)where F: Fn(&Data) -> Option<Msg> + 'static + Send + Sync, Msg: Send + 'static,

An alternative version of subscribe() that only send a message if the closure returns Some.

source

pub fn emit(&self, input: Data::Input)

Sends a message to the reducer to update its state.

If the Reducible::reduce() method returns true, all subscribers will be notified.

Trait Implementations§

source§

impl<Data: Debug + Reducible> Debug for Reducer<Data>

source§

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

Formats the value using the given formatter. Read more

Auto Trait Implementations§

§

impl<Data> RefUnwindSafe for Reducer<Data>

§

impl<Data> Send for Reducer<Data>where <Data as Reducible>::Input: Send,

§

impl<Data> Sync for Reducer<Data>where <Data as Reducible>::Input: Send,

§

impl<Data> Unpin for Reducer<Data>

§

impl<Data> UnwindSafe for Reducer<Data>

Blanket Implementations§

source§

impl<T> Any for Twhere T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<C> AsyncPosition<()> for C

source§

fn position(_index: usize)

Returns the position. Read more
source§

impl<T> Borrow<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> From<T> for T

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T> Instrument for T

source§

fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
source§

fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
source§

impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<C> Position<()> for C

source§

fn position(&self, _index: usize)

Returns the position. Read more
source§

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
source§

impl<T> WithSubscriber for T

source§

fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
source§

fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more