中

接上一篇优化home.js与about.js中的代码:

思路.jpg

优化思路.jpg

优化后about.js

import React from "react";
import { connect } from "../utils/connect";

import { decAction, subAction } from "../store/actionCreators";

function About(props) {
  return (
    <div>
      <hr />
      <h1>About</h1>
      <h2>当前计数: {props.counter}</h2>
      <button onClick={(e) => props.decrement()}>-1</button>
      <button onClick={(e) => props.subNumber(5)}>-5</button>
    </div>
  );
}

const mapStateToProps = (state) => {
  return {
    counter: state.counter,
  };
};
const mapDispatchToProps = (dispatch) => {
  return {
    decrement: function () {
      dispatch(decAction());
    },
    subNumber: function (num) {
      dispatch(subAction(num));
    },
  };
};

export default connect(mapStateToProps, mapDispatchToProps)(About);

优化后home.js与about.js一样，只是调用的action不一样;

//类组件home
import React, { PureComponent } from 'react';

import {connect} from '../utils/connect';
import {  incAction,  addAction } from '../store/actionCreators'

class Home extends PureComponent {
  render() {
    return (
      <div>
        <h1>Home</h1>
        <h2>当前计数: {this.props.counter}</h2>
        <button onClick={e => this.props.increment()}>+1</button>
        <button onClick={e => this.props.addNumber(5)}>+5</button>
      </div>
    )
  }
}

const mapStateToProps = state => ({
  counter: state.counter
})

const mapDispatchToProps = dispatch => ({
  increment() {
    dispatch(incAction());
  },
  addNumber(num) {
    dispatch(addAction(num));
  }
})

export default connect(mapStateToProps, mapDispatchToProps)(Home);

utils/connect.js

import React, { PureComponent } from "react";

import  store  from '../store';

export function connect(mapStateToProps, mapDispachToProp) {
  return function enhanceHOC(WrappedComponent) {
   return class extends PureComponent {
      constructor(props) {
        super(props);
        this.state = {
          storeState: mapStateToProps(store.getState())
        }
      }

      componentDidMount() {
        this.unsubscribe = store.subscribe(() => {
          this.setState({
            storeState: mapStateToProps(store.getState())
          })
        })
      }

      componentWillUnmount() {
        this.unsubscribe();
      }

      render() {
        return <WrappedComponent {...this.props}
          {...mapStateToProps(store.getState())}
          {...mapDispachToProp(store.dispatch)} />
      }
    }
  }
}

至此，封装完成了
思考:不止当前项目需要connect函数,那么最好的办法是把它封装成库，然后上传到npm，但是,当前还不够独立,因为它依赖了外部引入的store,也就是对业务逻辑有了依赖。问题：依然需要拿到store,但是不能通过导入的方式了。

解决方案:

手动封装库文件

utils/context.js

import React from 'react';

const StoreContext = React.createContext(); 

export {
  StoreContext
}

utils/connect.js

import React, { PureComponent } from "react";

import { StoreContext } from './context';

export function connect(mapStateToProps, mapDispachToProp) {
  return function enhanceHOC(WrappedComponent) {
    class EnhanceComponent extends PureComponent {
      constructor(props, context) {
        super(props, context);

        this.state = {
          storeState: mapStateToProps(context.getState())
        }
      }

      componentDidMount() {
        this.unsubscribe = this.context.subscribe(() => {
          this.setState({
            storeState: mapStateToProps(this.context.getState())
          })
        })
      }

      componentWillUnmount() {
        this.unsubscribe();
      }

      render() {
        return <WrappedComponent {...this.props}
          {...mapStateToProps(this.context.getState())}
          {...mapDispachToProp(this.context.dispatch)} />
      }
    }

    EnhanceComponent.contextType = StoreContext;

    return EnhanceComponent;
  }
}

src/index.js

import React from 'react';
import ReactDOM from 'react-dom';

import store from './store';
import { StoreContext } from './utils/context';
import App from './App';

ReactDOM.render(
  <StoreContext.Provider value={store}>
    <App />
  </StoreContext.Provider>,
  document.getElementById('root')
);

至此，到时候封装库的话只需要导出context与connect就行。

直接用第三方库文件

yarn add react-redux

src/index.js
对比自己封装的，使用时候会有一点点不一样

import React from 'react';
import ReactDOM from 'react-dom';

import store from './store';

// import { StoreContext } from './utils/context';
import { Provider } from 'react-redux';

import App from './App';

ReactDOM.render(
  <Provider store={store}>
    <App />
  </Provider>,
  document.getElementById('root')
);

pages/about.js与pages/home.js，均使用第三方的connect就行

import React from "react";
// import { connect } from "../utils/connect";
import { connect } from 'react-redux';

import { decAction, subAction } from "../store/actionCreators";

function About(props) {
  return (
    <div>
      <hr />
      <h1>About</h1>
      <h2>当前计数: {props.counter}</h2>
      <button onClick={(e) => props.decrement()}>-1</button>
      <button onClick={(e) => props.subNumber(5)}>-5</button>
    </div>
  );
}

const mapStateToProps = (state) => {
  return {
    counter: state.counter,
  };
};
const mapDispatchToProps = (dispatch) => {
  return {
    decrement: function () {
      dispatch(decAction());
    },
    subNumber: function (num) {
      dispatch(subAction(num));
    },
  };
};

export default connect(mapStateToProps, mapDispatchToProps)(About);