React-Redux源码解析（二） -- Provider

export function createProvider(storeKey = 'store', subKey) {
    const subscriptionKey = subKey || `${storeKey}Subscription`

    class Provider extends Component {
        getChildContext() {
          // 在这里将它赋值给this.context
          return { [storeKey]: this[storeKey], [subscriptionKey]: null }
        }

        constructor(props, context) {
          super(props, context)
          // 将外面传入的store赋值给this.store
          this[storeKey] = props.store;
        }

        render() {
         // Children.only用于获取仅有的一个子组件，多过或者少一一个都会报错
          return Children.only(this.props.children)
        }
    }

    if (process.env.NODE_ENV !== 'production') {
      Provider.prototype.componentWillReceiveProps = function (nextProps) {
        if (this[storeKey] !== nextProps.store) {
          warnAboutReceivingStore()
        }
      }
    }

    Provider.propTypes = {
        store: storeShape.isRequired,
        children: PropTypes.element.isRequired,
    }
    Provider.childContextTypes = {
        [storeKey]: storeShape.isRequired,
        [subscriptionKey]: subscriptionShape,
    }

    return Provider
}