Redux Observable Middleware is a lightweight Redux middleware designed for integrating RxJS-like observables directly into Redux action creators. It is currently in an early stage of development, with the latest stable version being `0.2.0`, published 10 years ago. While there isn't a defined release cadence, its purpose is to simplify handling asynchronous data streams by automatically subscribing to any object with a `subscribe` method found within an action's `observable` property. This package dispatches specific lifecycle actions (`_ON_NEXT`, `_ON_ERROR`, `_ON_COMPLETED` or custom types) as the observable emits values, completes, or errors. This approach differs from more comprehensive solutions like `redux-observable`, which utilizes "epics" for side effects, offering a simpler, direct method for incorporating observables into the Redux data flow.
npm install redux-observable-middlewareVerified import paths — ran on the pinned version, not inferred.
This quickstart demonstrates how to integrate an RxJS observable into a Redux action using `redux-observable-middleware`. It sets up a basic Redux store with the middleware, dispatches an action containing an observable that emits values every second, and logs the state changes as the observable progresses through its `ON_NEXT`, `ON_ERROR`, and `ON_COMPLETED` lifecycle actions.
Consider migrating to `redux-observable` (the actively maintained alternative) or extensively testing compatibility with a modern RxJS setup, adapting observable creation and operator chaining.
Review any existing logic that specifically depends on the timing or presence of the `onSubscribe` action relative to other lifecycle actions for an observable. Ensure your state updates or side effects correctly account for the `onSubscribe` action always being the first dispatched.
Always include `catchError` operators within your RxJS observable chains to handle errors gracefully before they propagate out of the observable. Dispatch an appropriate action within `catchError` to inform the Redux store of the error, as shown in `redux-observable` patterns. For example: `observable.pipe(map(data => ({ type: 'ON_NEXT', data })), catchError(err => of({ type: 'ON_ERROR', err })))`.Ensure that the `observable` property in your Redux action is an instance of an RxJS Observable or any object that implements a `subscribe` method. Double-check that `rxjs` is correctly imported and `Observable` instances are created correctly.
If using a string `type`, ensure your reducer handles both the original `ACTION_TYPE` and its suffixed variants (e.g., `ACTION_TYPE_ON_NEXT`). If using an object `type`, be explicit about which lifecycle actions you want to dispatch by defining `onSubscribe`, `onNext`, `onError`, `onCompleted` properties in the `type` object of your action.