Async Actions In the basics guide, we built a simple todo application. It was fully synchronous. Every time an action was dispatched, the state was updated immediately. In this guide, we will build a different, asynchronous application. It will use the Reddit API to show the current headlines for a selected subreddit. How does asynchronicity fit into Redux flow? Actions When you call an asynchronous API, there are two crucial moments in time: the moment you start the call, and the moment when y

Troubleshooting This is a place to share common problems and solutions to them. The examples use React, but you should still find them useful if you use something else. Nothing happens when I dispatch an action Sometimes, you are trying to dispatch an action, but your view does not update. Why does this happen? There may be several reasons for this. Never mutate reducer arguments It is tempting to modify the state or action passed to you by Redux. Don't do this! Redux assumes that you never mut

replaceReducer(nextReducer) Replaces the reducer currently used by the store to calculate the state. It is an advanced API. You might need this if your app implements code splitting, and you want to load some of the reducers dynamically. You might also need this if you implement a hot reloading mechanism for Redux. Arguments reducer (Function) The next reducer for the store to use.

Usage with React From the very beginning, we need to stress that Redux has no relation to React. You can write Redux apps with React, Angular, Ember, jQuery, or vanilla JavaScript. That said, Redux works especially well with libraries like React and Deku because they let you describe UI as a function of state, and Redux emits state updates in response to actions. We will use React to build our simple todo app. Installing React Redux React bindings are not included in Redux by default. You need

Managing Normalized Data As mentioned in Normalizing State Shape, the Normalizr library is frequently used to transform nested response data into a normalized shape suitable for integration into the store. However, that doesn't address the issue of executing further updates to that normalized data as it's being used elsewhere in the application. There are a variety of different approaches that you can use, based on your own preference. We'll use the example of adding a new Comment to a Post. St

Example: Todo List This is the complete source code of the tiny todo app we built during the basics tutorial. Entry Point index.js import React from 'react' import { render } from 'react-dom' import { Provider } from 'react-redux' import { createStore } from 'redux' import todoApp from './reducers' import App from './components/App' let store = createStore(todoApp) render( <Provider store={store}> <App /> </Provider>, document.getElementById('root') ) Action Creato

Using combineReducers Core Concepts The most common state shape for a Redux app is a plain Javascript object containing "slices" of domain-specific data at each top-level key. Similarly, the most common approach to writing reducer logic for that state shape is to have "slice reducer" functions, each with the same (state, action) signature, and each responsible for managing all updates to that specific slice of state. Multiple slice reducers can respond to the same action, independently update t

Reducers Actions describe the fact that something happened, but don't specify how the application's state changes in response. This is the job of a reducer. Designing the State Shape In Redux, all application state is stored as a single object. It's a good idea to think of its shape before writing any code. What's the minimal representation of your app's state as an object? For our todo app, we want to store two different things: The currently selected visibility filter; The actual list of tod

Store In the previous sections, we defined the actions that represent the facts about “what happened” and the reducers that update the state according to those actions. The Store is the object that brings them together. The store has the following responsibilities: Holds application state; Allows access to state via getState(); Allows state to be updated via dispatch(action); Registers listeners via subscribe(listener); Handles unregistering of listeners via the function returned by subscri

dispatch(action) Dispatches an action. This is the only way to trigger a state change. The store's reducing function will be called with the current getState() result and the given action synchronously. Its return value will be considered the next state. It will be returned from getState() from now on, and the change listeners will immediately be notified. A Note for Flux Users If you attempt to call dispatch from inside the reducer, it will throw with an error saying “Reducers may not dispa