react-redux源碼解析

一、 react-redux 和 redux是兩個東西。在做react項目的時候，一般用react-redux和redux搭配起來開發。redux主要是做數據、狀態的管理，而react-redux主要是方便數據redux在react使用。

二、源碼解析

1)、 入口文件index.js

 1 import Provider, { createProvider } from './components/Provider'
 2 import connectAdvanced from './components/connectAdvanced'
 3 import connect from './connect/connect'
 4 
 5 /*
 6     對外暴露的API
 7     Provider,
 8     createProvider,
 9     connectAdvanced,
10     connect,
11     根據每個APi追溯其源頭
12  */
13 export { Provider, createProvider, connectAdvanced, connect }

2)、Provider.js 

 1 import { Component, Children } from 'react'
 2 import PropTypes from 'prop-types'
 3 import { storeShape, subscriptionShape } from '../utils/PropTypes'
 4 import warning from '../utils/warning'
 5 
 6 let didWarnAboutReceivingStore = false
 7 function warnAboutReceivingStore() {
 8   if (didWarnAboutReceivingStore) {
 9     return
10   }
11   didWarnAboutReceivingStore = true
12 
13   warning(
14     '<Provider> does not support changing `store` on the fly. ' +
15     'It is most likely that you see this error because you updated to ' +
16     'Redux 2.x and React Redux 2.x which no longer hot reload reducers ' +
17     'automatically. See https://github.com/reduxjs/react-redux/releases/' +
18     'tag/v2.0.0 for the migration instructions.'
19   )
20 }
21 // 對外暴露 createProvider 方法 。
22 export function createProvider(storeKey = 'store', subKey) {
23     const subscriptionKey = subKey || `${storeKey}Subscription`
24 
25     // 定義一個Provider類
26     class Provider extends Component {
27         getChildContext() {
28           return { [storeKey]: this[storeKey], [subscriptionKey]: null }
29         }
30 
31         constructor(props, context) {
32           super(props, context)
33           this[storeKey] = props.store;
34         }
35         // 其實就是頂層組件
36         render() {
37           return Children.only(this.props.children)
38         }
39     }
40 
41     if (process.env.NODE_ENV !== 'production') {
42       Provider.prototype.componentWillReceiveProps = function (nextProps) {
43         if (this[storeKey] !== nextProps.store) {
44           warnAboutReceivingStore()
45         }
46       }
47     }
48 
49     Provider.propTypes = {
50         store: storeShape.isRequired,
51         children: PropTypes.element.isRequired,
52     }
53     Provider.childContextTypes = {
54         [storeKey]: storeShape.isRequired,
55         [subscriptionKey]: subscriptionShape,
56     }
57 
58     return Provider
59 }
60 
61 // 對外暴露Provider 組件   createProvider() => Provider;
62 export default createProvider()

3)、connect.js

 1 import connectAdvanced from '../components/connectAdvanced'
 2 import shallowEqual from '../utils/shallowEqual'
 3 import defaultMapDispatchToPropsFactories from './mapDispatchToProps'
 4 import defaultMapStateToPropsFactories from './mapStateToProps'
 5 import defaultMergePropsFactories from './mergeProps'
 6 import defaultSelectorFactory from './selectorFactory'
 7 
 8 /*
 9   connect is a facade over connectAdvanced. It turns its args into a compatible
10   selectorFactory, which has the signature:
11 
12     (dispatch, options) => (nextState, nextOwnProps) => nextFinalProps
13   
14   connect passes its args to connectAdvanced as options, which will in turn pass them to
15   selectorFactory each time a Connect component instance is instantiated or hot reloaded.
16 
17   selectorFactory returns a final props selector from its mapStateToProps,
18   mapStateToPropsFactories, mapDispatchToProps, mapDispatchToPropsFactories, mergeProps,
19   mergePropsFactories, and pure args.
20 
21   The resulting final props selector is called by the Connect component instance whenever
22   it receives new props or store state.
23  */
24 
25 function match(arg, factories, name) {
26   for (let i = factories.length - 1; i >= 0; i--) {
27     const result = factories[i](arg)
28     if (result) return result
29   }
30 
31   return (dispatch, options) => {
32     throw new Error(`Invalid value of type ${typeof arg} for ${name} argument when connecting component ${options.wrappedComponentName}.`)
33   }
34 }
35 
36 function strictEqual(a, b) { return a === b }
37 
38 // createConnect with default args builds the 'official' connect behavior. Calling it with
39 // different options opens up some testing and extensibility scenarios
40 // 對外暴露crateConnect方法
41 export function createConnect({
42   connectHOC = connectAdvanced,
43   mapStateToPropsFactories = defaultMapStateToPropsFactories,
44   mapDispatchToPropsFactories = defaultMapDispatchToPropsFactories,
45   mergePropsFactories = defaultMergePropsFactories,
46   selectorFactory = defaultSelectorFactory
47 } = {}) {
48   // 返回一個connect函數。 接收 mapStateToProps, mapDispatchToProps, megeProps等等參數
49   return function connect(
50     mapStateToProps,
51     mapDispatchToProps,
52     mergeProps,
53     {
54       pure = true,
55       areStatesEqual = strictEqual,
56       areOwnPropsEqual = shallowEqual,
57       areStatePropsEqual = shallowEqual,
58       areMergedPropsEqual = shallowEqual,
59       ...extraOptions
60     } = {}
61   ) {
62     const initMapStateToProps = match(mapStateToProps, mapStateToPropsFactories, 'mapStateToProps')
63     const initMapDispatchToProps = match(mapDispatchToProps, mapDispatchToPropsFactories, 'mapDispatchToProps')
64     const initMergeProps = match(mergeProps, mergePropsFactories, 'mergeProps')
65     // 調用connectHOC方法
66     return connectHOC(selectorFactory, {
67       // used in error messages
68       methodName: 'connect',
69 
70        // used to compute Connect's displayName from the wrapped component's displayName.
71       getDisplayName: name => `Connect(${name})`,
72 
73       // if mapStateToProps is falsy, the Connect component doesn't subscribe to store state changes
74       shouldHandleStateChanges: Boolean(mapStateToProps),
75 
76       // passed through to selectorFactory
77       initMapStateToProps,
78       initMapDispatchToProps,
79       initMergeProps,
80       pure,
81       areStatesEqual,
82       areOwnPropsEqual,
83       areStatePropsEqual,
84       areMergedPropsEqual,
85 
86       // any extra options args can override defaults of connect or connectAdvanced
87       ...extraOptions
88     })
89   }
90 }
91 
92 export default createConnect()