调度到中间件链的开始？
我正在编写一个需要调度thunk动作的定制中间件。 问题是中间件是在中间件链中的redux-thunk之后调用的，所以我得到错误Uncaught Error: Actions must be plain objects. Use custom middleware for async actions. Uncaught Error: Actions must be plain objects. Use custom middleware for async actions. 当使用提供的dispatch 。
export default function createMiddleware() {
return ({dispatch, getState}) => next => (action) => {
if(action.type !== 'FOO') {
return next(action);
}
dispatch(thunkActionHere); // this is the issue
}
}
我希望将这个thunk动作发回到中间件链的开头，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;
}
我无法在redux-thunk之前放置我的中间件，因为它不会收到thunk派发的操作。
在中间件链中进行调度会将操作发送到中间件链的开始，并像往常一样调用thunk（演示 - 查看控制台）。
为什么？
原始的store.dispatch() （在应用中间件之前）检查操作是否为普通POJO，如果不是，则会引发错误：
function dispatch(action) {
if (!isPlainObject(action)) {
throw new Error(
'Actions must be plain objects. ' +
'Use custom middleware for async actions.'
)
}
当你使用applyMiddleware() ， dispatch被一个新的方法取代，这个方法是中间件的链，最后调用原始的store.dispatch() 。 你可以在applyMiddleware方法中看到它：
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 - 改变你的中间件，因为第一个函数将阻止你的中间件工作。
export default const createMiddleware = ({dispatch, getState}) => next => (action) => {
if(action.type !== 'FOO') {
return next(action);
}
dispatch(thunkActionHere); // this is the issue
}
原来问题出在我的商店配置中。 使用redux的compose引起了这个问题。
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())
));
}
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));
}
我们使用redux-devtools-extension中的composeWithDevTools 。 与上述相同的问题和解决方案。 只需要移动到使用applyMiddleware(...middlewares)而不是多个applyMiddleware(middleware), applyMiddleware(middleware)作为参数的组成。