bindActionCreators就是给action创建函数绑定了dispatch,
可以直接以普通函数执行,而不用dispatch(actionCreator)这样写.
比如下面,bindActionCreators生成一个对象,对象里面的value值是function,
那么可以直接this.boundActionCreators.addTodo()执行**
function bindActionCreator(actionCreator, dispatch) {
return (...args) => dispatch(actionCreator(...args))
}
/**
* Turns an object whose values are action creators, into an object with the
* same keys, but with every function wrapped into a `dispatch` call so they
* may be invoked directly. This is just a convenience method, as you can call
* `store.dispatch(MyActionCreators.doSomething())` yourself just fine.
*
* 将一个value值是action创建函数的对象变成一个具有相同key值的对象,但是每个函数都被封装到
* `dispatch`回调里面,这样它们就有可能被直接触发. 这样只是比较方便,你也可以调用
* `store.dispatch(MyActionCreators.doSomething())`
*
* For convenience, you can also pass a single function as the first argument,
* and get a function in return.
*
* 为了方便,你也可以传单个函数作为第一个参数,然后返回一个函树
*
* @param {Function|Object} actionCreators An object whose values are action
* creator functions. One handy way to obtain it is to use ES6 `import * as`
* syntax. You may also pass a single function.
*
* actionCreators 是一个value值是action创建函数的对象,一个很方便获取到它的方法就是
* 使用ES6 的`import * as `语法.也可以传单个函数
*
* @param {Function} dispatch The `dispatch` function available on your Redux
* store.
*
* dispatch就是redux 里store的dispatch
*
* @returns {Function|Object} The object mimicking the original object, but with
* every action creator wrapped into the `dispatch` call. If you passed a
* function as `actionCreators`, the return value will also be a single
* function.
*
* 返回的对象和初始的对选象很像,但每一个action创建函数都给封装到`dispatch`回调里面
* 如果你传单个函数作为`actionCreators`,那返回值也是一个单个函数
*/
export default function bindActionCreators(actionCreators, dispatch) {
if (typeof actionCreators === 'function') {
return bindActionCreator(actionCreators, dispatch)
}
if (typeof actionCreators !== 'object' || actionCreators === null) {
throw new Error(
`bindActionCreators expected an object or a function, instead received ${actionCreators === null ? 'null' : typeof actionCreators}. ` +
`Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?`
)
//bindActionCreators的参数应该是对象或者函数,而不是空或其他类型,
//你是不是把"import * as ActionCreators from"写成了"import ActionCreators from"?
}
const keys = Object.keys(actionCreators)
const boundActionCreators = {}
for (let i = 0; i < keys.length; i++) {
const key = keys[i]
const actionCreator = actionCreators[key]
if (typeof actionCreator === 'function') {
boundActionCreators[key] = bindActionCreator(actionCreator, dispatch) //就是(...args) => dispatch(actionCreator(...args))
}
}
return boundActionCreators
} 