![]() ![]() The most common async middleware is redux-thunk, which lets you write plain functions that may contain async logic directly. There are many kinds of async middleware for Redux, and each lets you write your logic using different syntax. This allows you to write code that can dispatch actions and check the store state, while keeping that logic separate from your UI. The most common reason to use middleware is to allow different kinds of async logic to interact with the store. Teach dispatch how to accept other values besides plain action objects, such as functions and promises, by intercepting them and dispatching real action objects instead.Write extra code that has access to dispatch and getState.Pause, modify, delay, replace, or halt dispatched actions.Execute extra logic when any action is dispatched (such as logging the action and state).Any asynchronicity has to happen outside the store.īut, what if you want to have async logic interact with the store by dispatching or checking the current store state? That's where Redux middleware come in. It only knows how to synchronously dispatch actions, update the state by calling the root reducer function, and notify the UI that something has changed. Thunks and Async Logic Using Middleware to Enable Async Logic īy itself, a Redux store doesn't know anything about async logic. See the CodeSandbox projects and the tutorial-steps branch in the project repo for the complete changes in the application. If you want to reset that, delete the 'randomTimestampSeed' value in your browser's Local Storage and reload the page, or you can turn that off by editing src/api/server.js and setting useSeededRNG to false.Īs a reminder, the code examples focus on the key concepts and changes for each section. We'll use the client object to make HTTP calls to our in-memory fake REST API for this section.Īlso, the mock server has been set up to reuse the same random seed each time the page is loaded, so that it will generate the same list of fake users and fake posts. The project also includes a small HTTP API client object that exposes client.get() and client.post() methods, similar to popular HTTP libraries like axios. The API uses /fakeApi as the base URL for the endpoints, and supports the typical GET/POST/PUT/DELETE HTTP methods for /fakeApi/posts, /fakeApi/users, and fakeApi/notifications. To keep the example project isolated but realistic, the initial project setup already includes a fake in-memory REST API for our data (configured using the Mock Service Worker mock API tool). We'll cover how to use RTK Query starting in Part 7: RTK Query Basics. We specifically teach RTK Query as the default approach for data fetching, and RTK Query is built on the same patterns shown in this page. RTK Query is a purpose built data fetching and caching solution for Redux apps, and can eliminate the need to write any thunks or reducers to manage data fetching. ![]() The above example uses compression streams to compress arbitrary data using gzip.Redux Toolkit includes the RTK Query data fetching and caching API. pipeThrough ( new CompressionStream ( 'gzip' ) ). getReader ( ) Ĭonst = new TransformStream ( ) ![]() ![]() They allow you to access parts of a response as they arrive from the server: const response = await fetch (url ) Ĭonst reader = response. Response streams have been available in all modern browsers for a while now. Yeah ok it isn't the most imaginative example, I just wanted to keep it simple, okay?Īnyway, how does this work? # Previously on the exciting adventures of fetch streams This shows how you can stream data from the user to the server, and send data back that can be processed in real time. ![]()
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