redux-semaphore v1.0.3

redux-semaphore

Ever wanted to wait for some action to happen in redux? redux-semaphore is yet another way to do it.

Usage

Obviously, first thing you need to do is to install it:

npm install --save redux-semaphore

Then, in your store configuration script, you need to create and use semaphore middleware:

import {createStore, applyMiddleware} from 'redux';
import {createSemaphoreMiddleware} from 'redux-semaphore';

import reducer from './reducers';

// Create middleware
// For now middleware factory doesn't take any parameters 
const semaphoreMiddleware = createSemaphoreMiddleware();

export const store = createStore(
    reducer,
    applyMiddleware(semaphoreMiddleware)
);

And finally, somewhere in your code, you can do this:

import {
    INITIAL_PROCESS_ACTION,
    TERMINAL_PROCESS_ACTION
    // ...
} from './constants/actionTypes';
import {semaphore} from 'redux-semaphore';

// You don't have to use async/await.
// Good ol' semaphore().then will work too
async function theProcess() {
    // Start some async process by firing initial action
    // It can be some saga, or whatever you want
    store.dispatch({ type: INITIAL_PROCESS_ACTION });

    // Wait for terminal action to be dispatched
    const terminalAction = await semaphore(TERMINAL_PROCESS_ACTION);

    // Also you can pass a function to check actions
    const terminalAction = await semaphore(action => {
        return action.type === TERMINAL_PROCESS_ACTION && action.transactionId === transactionId;
    });

    // Furthermore, if you want for semaphore to fail, you can pass second action checker
    try {
        store.dispatch({ type: INITIAL_PROCESS_ACTION });    
        const success = await semaphore(PROCESS_SUCCESS_ACTION, PROCESS_FAIL_ACTION);
    } catch (error) {
        console.warn('Process failed with error: ' + error);
    }

    // Also composition goodies from native Promise class will work
    const result = await Promise.race([
        semaphore(TERMINAL_PROCESS_ACTION),
        semaphore(PROCESS_CANCEL_ACTION),
    ]);
}

And that's about it. Nothing special here. Open index.js and see for yourself.

Motivation

Original intention for this lib was to get some way to wait until some saga finishes. Given examples above, those who are familiar with redux-saga, already noticed that in fact, await semaphore(action) is a "lite" version of yield take(action) in sagas.