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    0.1.0 • Public • Published

    rx-ducks-middleware (alpha)

    ** WARNING: This module is purely experimental **

    Creates RxJS 5-based middleware for Redux.

    • Dispatch a function that returns an observable of actions, a promise of action or iterable of actions.
    • Function is provided a stream of all actions, useful for composition with the current dispatched observable (think things like takeUntil or zip)
    • Function is also provided a reference to the store which can be used to get the state or even dispatch.


    NOTE: This has a peer dependencies of rxjs@5.0.* and redux, which will have to be installed as well.

    npm i -S rx-ducks-middleware



    With rxDucksMiddleware, you can dispatch any function that returns an observable, a promise, an observable-like object or an iterable. The basic call looks like:

    // using RxJS
    dispatch(() => Rx.Observable.of({ type: 'ASYNC_ACTION_FROM_RX' }).delay(1000));
    // using a Promise
    dispatch(() => Promise.resolve({ type: 'ASYNC_ACTION_FROM_PROMISE'}));
    // using an Array of actions
    dispatch(() => [{ type: 'ACTION_1' }, { type: 'ACTION_2' }]);
    // using a generator of actions
    dispatch(() => (function* () {
      for (let i = 0; i < 10; i++) {
        yield { type: 'SOME_GENERATED_ACTION', value: i };


    It's recommended to dispatch an action to cancel your async action with Rx. This can be done by leveraging the first argument to your dispatched function, which returns all actions. With that you can use takeUntil to abort the async action cleanly and via composition.

    dispatch((actions) => Observable.timer(1000)
      .map(() => ({ type: 'TIMER_COMPLETE'}))
      .takeUntil(actions.filter(a => a.type === 'ABORT_TIMER')))
    // elsewhere in your code you can abort with a simple dispatch
    dispatch({ type: 'ABORT_TIMER' });

    You can also cancel an async dispatch by using the return value from your dispatch, which is an Rx Subscription. This works well for other types that don't have cancellation, like promises, but internally will really use "disinterest" to stop the resolved value from propagating.

    let subscription = dispatch(() => Promise.resolve({ type: 'DELAYED_ACTION' }));
    // will stop DELAYED_ACTION from firing

    Other API Notes

    The second argument to your dispatched function will be the store instance itself. This gives you the ability to getState() on your store in case you need to assert some condition before dispatching your next async message. It also gives you the ability to dispatch() explicitly.

    Basic Dispatch Type Signature

    If it helps to think about it this way, in a TypeScript-style type definition, the dispatch function would look like this when used to dispatch an action asynchronously:

    dispatch = ((actions?: Observable<Action>, store?: ReduxStore) => Observable<Action>) => Subscription;


    Below is a basic example of it how it might work in React.

    import { Component } from 'react';
    import { connect } from 'react-redux';
    import { createStore, applyMiddleware } from 'redux';
    import { rxDucksMiddleware } from 'rx-ducks-middleware';
    import * as Rx from 'rxjs';
    // Just the plain redux reducer.
    const reducer = (state = {}, action) => {
      switch (action.type) {
        case 'DATA_LOADING':
          return { ...state, loading: true };
        case 'DATA_LOADED':
          return { ...state, loading: false, data: };
        case 'ABORT_LOAD':
          return { ...state, loading: false };
      return state;
    // making a store
    const store = createStore(reducer, applyMiddleware(rxDucksMiddleware()));
    const loadData = () => (actions, store) => Observable.of('hello world')
                    .map(data => ({ type: 'DATA_LOADED', data })
                    .startWith({ type: 'DATA_LOADING' })
                    .takeUntil(actions.filter(a => a.type === 'ABORT_LOAD'));
    // plain old action
    const abortLoad = () => ({ type: 'ABORT_LOAD' });
    const mapStateToProps = ({ data, loading }) => ({ data, loading });
    const mapDispatchToProps = (dispatch) => ({
      loadData: () => dispatch(loadData()),
      abortLoad: () => dispatch(abortLoad())
    const MyComponent = ({ loading, data, loadData, abortLoad }) => (
        <button onClick={loadData}>load data</button>
        <button onClick={abortLoad}>abort load</button>
        <div>Loading: {loading}</div>
        <pre>{JSON.stringify(data, null, 2)}</pre>
    export default connect(mapStateToProps, mapDispatchToProps)(MyComponent);



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