provider 源码

import { Component, Children } from 'react'
import PropTypes from 'prop-types'
import storeShape from '../utils/storeShape'
import warning from '../utils/warning'
let didWarnAboutReceivingStore = falsefunction warnAboutReceivingStore() {if (didWarnAboutReceivingStore) {return}didWarnAboutReceivingStore = truewarning('<Provider> does not support changing `store` on the fly. ' +'It is most likely that you see this error because you updated to ' +'Redux 2.x and React Redux 2.x which no longer hot reload reducers ' +'automatically. See https://github.com/reactjs/react-redux/releases/' +'tag/v2.0.0 for the migration instructions.')
}export default class Provider extends Component {getChildContext() {return { store: this.store }}constructor(props, context) {super(props, context)this.store = props.store}render() {return Children.only(this.props.children)}
}if (process.env.NODE_ENV !== 'production') {Provider.prototype.componentWillReceiveProps = function (nextProps) {const { store } = thisconst { store: nextStore } = nextPropsif (store !== nextStore) {warnAboutReceivingStore()}}
}Provider.propTypes = {store: storeShape.isRequired,children: PropTypes.element.isRequired
}
Provider.childContextTypes = {store: storeShape.isRequired
}

首先学习react数据传递三种方法，props，state，context

props：一般用于将父组件数据传递到子组件，不能跨组件传递

state：state是内部状态或者局部状态
           es6数据解析操作，let {xxx ,xx, x} = this.state;

context: 和props相比，context可以跨组件传递信息

声明context步骤一：

constructor(props, context) {super(props, context)this.store = props.store}getChildContext() {return { store: this.store }}

更具react生命周期，首先constructor方法获取属性store，getChildContext()将store放入context中

步骤二：

Provider.propTypes = {store: storeShape.isRequired,children: PropTypes.element.isRequired
}

验证组件信息

步骤三：

Provider.childContextTypes = {store: storeShape.isRequired
}

声明了childrenContextTypes。如果不声明的话，将无法在组件中使用getChildContext()方法；

获取context：

子树中的任何组件都可以通过定义ContextTypes 去访问它。

connect中通过

  Connect.contextTypes = {store: storeShape}

然后通过constructor获取store

constructor(props, context) {super(props, context)this.version = versionthis.store = props.store || context.storeconst storeState = this.store.getState()this.state = { storeState }this.clearCache()}

最后执行render渲染，返回一个react子元素。Children.only是react提供的方法，this.props.children表示的是只有一个root的元素。