自定义 Redux 中间件 - 派发到中间件链的开头？

Question

我正在编写一个需要分派 thunk 操作的自定义中间件。问题是中间件在中间件链中的 redux-thunk 之后被调用，所以在使用提供的 dispatch.

时出现错误 Uncaught Error: Actions must be plain objects. Use custom middleware for async actions.

export default function createMiddleware() {
    return ({dispatch, getState}) => next => (action) => {
        if(action.type !== 'FOO') {
            return next(action);
        }

        dispatch(thunkActionHere); // this is the issue
    }
}

我想将此 thunk 操作分派回中间件链的开头，以便 redux-thunk 可以处理它。这可能吗？

更新：

function createMiddleware(extraArgument) {
    return function ({dispatch, getState}) {
        return function (next) {
            return function (action) {
                switch (action.type) {
                    case 'FOO1':
                        dispatch({type: 'NORMAL_ACTION'}); // works fine
                        break;
                    case 'FOO2':
                        dispatch(function() {
                            return (dispatch, getState) => { // Error: Actions must be plain objects. Use custom middleware for async actions.
                                console.log('inside the thunk');
                            };
                        });
                        break;
                    default:
                        return next(action);
                }
            };
        };
    };
}

const middleware = createMiddleware();
middleware.withExtraArgument = createMiddleware;

export default middleware;

这是我的商店配置：

export default function configureStore(initialState) {
    const store = createStore(rootReducer, initialState, compose(
        // Add other middleware on this line...
        applyMiddleware(bugsnagErrorCatcherMiddleware()),
        applyMiddleware(thunk.withExtraArgument({APIFactory, PusherManager})),
        applyMiddleware(webrtcVideoMiddleware.withExtraArgument(PusherManager)), // this is the middleware above
        applyMiddleware(bugsnagbreadcrumbLoggerMiddleware()),
        )
    );

    return store;
}

我不能将我的中间件放在 redux-thunk 之前，因为那样它就不会收到 thunk 调度的操作。

Answer 1

中间件链内部的调度会将操作发送到中间件链的开头，并像往常一样调用 thunk（Demo - 查看控制台）。

为什么？

原来的store.dispatch()（在应用中间件之前）检查动作是否是普通的POJO，如果不是则抛出错误：

  function dispatch(action) {
    if (!isPlainObject(action)) {
      throw new Error(
        'Actions must be plain objects. ' +
        'Use custom middleware for async actions.'
      )
    }

当您 applyMiddleware() 时，dispatch 被一个新方法取代，该方法是中间件链，最终调用原始 store.dispatch()。在applyMiddleware方法中可以看到：

export default function applyMiddleware(...middlewares) {
  return (createStore) => (reducer, preloadedState, enhancer) => {
    const store = createStore(reducer, preloadedState, enhancer)
    let dispatch = store.dispatch // dispatch is now the original store's dispatch
    let chain = []

    const middlewareAPI = {
      getState: store.getState,
      dispatch: (action) => dispatch(action) // this refers to the dispatch variable. However, it's not the original dispatch, but the one that was created by compose
    }
    chain = middlewares.map(middleware => middleware(middlewareAPI))
    dispatch = compose(...chain)(store.dispatch) // dispatch is a composition of the chain, with the original dispatch in the end

    return {
      ...store,
      dispatch
    }
  }
}

顺便说一句 - 将您的中间件更改为此，因为第一个函数将阻止您的中间件工作。

export default const createMiddleware = ({dispatch, getState}) => next =>   (action) => {
    if(action.type !== 'FOO') {
        return next(action);
    }

    dispatch(thunkActionHere); // this is the issue
}

Answer 2

原来问题出在我的商店配置上。使用 redux 的 compose 导致了这个问题。

之前：

import {createStore, applyMiddleware, compose} from 'redux';
import thunk from 'redux-thunk';
import rootReducer from '../redux/reducers';
import webrtcVideoMiddleware from '../redux/middleware/webrtcVideo';
import bugsnagErrorCatcherMiddleware from '../redux/middleware/bugsnag/errorCatcher';
import bugsnagbreadcrumbLoggerMiddleware from '../redux/middleware/bugsnag/breadcrumbLogger';
import * as APIFactory from '../services/APIFactory';
import Pusher from '../services/PusherManager';

const PusherManager = new Pusher(false);

export default function configureStore(initialState) {
    return createStore(rootReducer, initialState, compose(
        applyMiddleware(bugsnagErrorCatcherMiddleware()),
        applyMiddleware(thunk.withExtraArgument({APIFactory, PusherManager})),
        applyMiddleware(webrtcVideoMiddleware(PusherManager)),
        applyMiddleware(bugsnagbreadcrumbLoggerMiddleware())
    ));
}

之后：

import {createStore, applyMiddleware} from 'redux';
import thunk from 'redux-thunk';
import rootReducer from '../redux/reducers';
import webRTCVideoMiddleware from '../redux/middleware/webrtcVideo';
import bugsnagErrorCatcherMiddleware from '../redux/middleware/bugsnag/errorCatcher';
import bugsnagBreadcrumbLoggerMiddleware from '../redux/middleware/bugsnag/breadcrumbLogger';
import * as APIFactory from '../services/APIFactory';
import Pusher from '../services/PusherManager';

const PusherManager = new Pusher(false);

export default function configureStore(initialState) {
    const middleware = [
        bugsnagErrorCatcherMiddleware(),
        thunk.withExtraArgument({APIFactory, PusherManager}),
        webRTCVideoMiddleware.withExtraArgument(PusherManager),
        bugsnagBreadcrumbLoggerMiddleware(),
    ];

    return createStore(rootReducer, initialState, applyMiddleware(...middleware));
}

Answer 3

我们使用 redux-devtools-extension 中的 composeWithDevTools。与上述相同的问题和相同的解决方案。只需要移动到使用 applyMiddleware(...middlewares) 而不是多个 applyMiddleware(middleware), applyMiddleware(middleware) 作为组合的参数。

自定义 Redux 中间件 - 派发到中间件链的开头？

Custom Redux Middleware - Dispatch to beginning of middleware chain?

node.js

reactjs

redux

react-redux

redux-thunk