redux bindActionCreators

function bindActionCreator(actionCreator, dispatch) {
 //其实，bindActionCreators的核心代码就是在这里，让每一个action函数最外层都被store.dispatch包含。
 //这样就可以保障action函数在任何地方都可以被调用。
  return (...args) => dispatch(actionCreator(...args))
}

//在这里处理actionCreators中的每一个函数，将每一个函数的最外层都包一层store.dispatch
//一调用action函数实际调用的是store.dispatch（action（））进行处理。

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"?`
    )
  }

  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)
    }
  }
  return boundActionCreators
}