React 高阶组件（HOC）

高阶组件（HOC）是 React 中用于复用组件逻辑的一种高级技巧。

1. 简单用法

import React, { Component } from "react";

const withMouse = (AppComponent) => {
  class HOC extends Component {
    constructor(props) {
      super(props);
      this.state = { x: 0, y: 0 };
    }

    bindMouseMove = (event) => {
      this.setState({
        x: event.clientX,
        y: event.clientY,
      });
    };

    render() {
      return (
        <div
          style={{ border: "1px solid #eee", height: 400,  400 }}
          onMouseMove={this.bindMouseMove}
        >
          <h5>高阶组件</h5>
          <AppComponent {...this.props} mousePosition={this.state} />
        </div>
      );
    }
  }
  return HOC;
};

const App = (props) => {
  const { x, y } = props.mousePosition;
  return (
    <p>
      mousePosition position is ({x}, {y})
    </p>
  );
};


<!--高阶组件 withMouse -->
export default withMouse(App);

redux 中 connect

import { connect } from "react-redux";

const TodoList = connect(mapStateToProps, mapDispatchToProps)(TodoList);

export default TodoList;

connect也是一个高阶组件：

export const connect = (mapStateToProps, mapDispatchToProps) => (
  WrappedComponent
) => {
  class Connect extends Component {
    constructor(props) {
      super(props);
      this.state = {
        allProps: {},
      };
    }

    /* 
    中间省略公共逻辑 
    mapStateToProps = (state) => {
        return { allProps: state.allProps };
    };

    mapDispatchToProps = (dispatch) => {
        return { ... };
    }; 
    */
    render() {
      return <WrappedComponent {...this.state.allProps} />;
    }
  }
  return Connect;
};