Redux源码createStore解读常用方法

传入参数

• reducer，reducer行为函数
• preloadedState，初始化state数据
• enhancer，使用（中间件等），不常用

const store = createStore(reducer, [preloadedState], enhancer);

getState

直接返回当前currentState，获取state值，@return state（我觉得应该深克隆一个新的对象返回，不然有可能会被外部修改）

function getState() {
     
    if (isDispatching) {
     
        throw new Error('....');
    }
    // console.log(currentState);

    return currentState;
}

dispatch派发行为

执行派发行为，就会在内部执行reducer并且执行之前准备发布的函数listener ，@params action行为，@return action行为

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

        if (typeof action.type === 'undefined') {
     
            throw new Error('Actions may not have an undefined "type" property. ' + 'Have you misspelled a constant?');
        }

        if (isDispatching) {
     
            throw new Error('Reducers may not dispatch actions.');
        }

        try {
     
            isDispatching = true;
            currentState = currentReducer(currentState, action);
            //执行reducer函数，会在创建的时候dispatch把刚开始的preloadedState传进来执行
        } finally {
     
            isDispatching = false;
        }

        var listeners = currentListeners = nextListeners;

        for (var i = 0; i < listeners.length; i++) {
     
            var listener = listeners[i];
            listener();//发布订阅
        }

        return action;
    }

subscribe函数

redux发布订阅

• 传入参数时@params function
• 并用闭包保存数据，最后可以删除，@return function unsubscribe

function subscribe(listener) {
     
        if (typeof listener !== 'function') {
     //判断s listener是否函数
            throw new Error('Expected the listener to be a function.');
        }

        if (isDispatching) {
     //判断是否派发
            throw new Error('You may not call store.subscribe() while the reducer is executing. ' + 'If you would like to be notified after the store has been updated, subscribe from a ' + 'component and invoke store.getState() in the callback to access the latest state. ' + 'See https://redux.js.org/api-reference/store#subscribelistener for more details.');
        }

        var isSubscribed = true;
        ensureCanMutateNextListeners();
        nextListeners.push(listener);//把函数压入栈
        return function unsubscribe() {
     
            if (!isSubscribed) {
     
                return;
            }

            if (isDispatching) {
     
                throw new Error('You may not unsubscribe from a store listener while the reducer is executing. ' + 'See https://redux.js.org/api-reference/store#subscribelistener for more details.');
            }

            isSubscribed = false;
            ensureCanMutateNextListeners();
            var index = nextListeners.indexOf(listener);
            nextListeners.splice(index, 1);
            //删除数组里面的函数，如果连续删除容易造成数组塌陷
            currentListeners = null;
        };
    }

如果有错，望大佬指出。。。