Redux-React 代码原理分析

Posted 2020-11-22

目标
react使用redux的主要目的是：
1）实现简洁统一的状态维护，提高代码可维护性；
2）实现简洁的注入依赖，避免重重传递参数；
Plug Any Data Into Any Component. This is the problem that Redux solves. It gives components direct access to the data they need.
3）实现自动化渲染。

index.js
应用的入口代码

import React from ‘react‘;
import { render } from ‘react-dom‘;
import Counter from ‘./Counter‘;
import { Provider } from ‘react-redux‘;
import { createStore } from ‘redux‘;

const initialState = {
count: 0
};

function reducer(state = initialState, action) {
switch(action.type) {
case ‘INCREMENT‘:
return {
count: state.count + 1
};
case ‘DECREMENT‘:
return {
count: state.count - 1
};
default:
return state;
}
}

/**

• 1） 创建全局存储对象 store,传入合适的reducer.
  */
  const store = createStore(reducer);

/**

• 2） 将store实例绑定到 App
  */

const App = () => (
<Provider store={store}>
<Counter/>
</Provider>
);

render(<App />, document.getElementById(‘root‘));
组件代码
import React from ‘react‘;
import { connect } from ‘react-redux‘;

/**

• index.js创建的store全局对象，会注入到所有下级对象中，因此这里才可以使用dispatch函数来改变属性。
  */
  class Counter extends React.Component {
  increment = () => {
  //实际上是调用全局store对象的dispatch函数
  this.props.dispatch({ type: ‘INCREMENT‘ });
  }

  decrement = () => {
  this.props.dispatch({ type: ‘DECREMENT‘ });
  }

  render() {
  return (
  <div>
  <h2>Counter</h2>
  <div>
  <button onClick={this.decrement}>-</button>
  <span>{this.props.count}</span>
  <button onClick={this.increment}>+</button>
  </div>
  </div>
  )
  }
  }

//具体的属性转换函数
function mapStateToProps(state) {
return {
count: state.count
};
}

//通过connect方法将store的state属性转换成本组件的属性
export default connect(mapStateToProps)(Counter);