React学习笔记高阶

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React官方文档也一直没看完，sigh

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Render Props

What is render prop

  • a technique for sharing code between React components using a prop whose value is a function

  • A component with a render prop takes a function that returns a React element and calls it instead of implementing its own render logic:

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    <DataProvider render={data => (<h1>Hello {data.target}</h1>)}

Why render prop?

  • in react, state of components does not share automatically

  • to make components reusable, sometimes, we have to pass the state of component A to component B, without embedding it in the component A, in order to use A’s state

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    class Cat extends React.Component {
      render() {
        const mouse = this.props.mouse
        return (
        	<img src='/cat.jpg' style={{ position: 'absolute', left: mouse.x, top: mouse.y }}
        )
      }
    }
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    class Mouse extends React.Component {
      constructor(props) {
        super(props)
        this.handleMouseMove = this.handleMouseMove.bind(this)
        this.state = { x: 0, y: 0 }
      }
      
      handleMouseMove(event) {
        this.setState({
          x: event.clientX,
          y: event.clientY,
        })
      }
      
      render() {
        return (
        	<div style={{ height: '100%' }} onMouseMove={this.handleMouseMove}>
        		{this.props.render(this.state)}
        	</div>
        )
      }
    }

    class MouseTracker extends React.Component {
      render() {
        return (
        	<div>
        		<h1>Move the mouse around!</h1>
        		<Mouse render={mouse => (
        			<Cat mouse={mouse} />
        		)}/>
        	</div>
        )
      }
    }

  • a render prop is a function prop that a component uses to know what to render

Using tips

  • any prop that is a function that a component uses to know what to render is technically a “render prop”, it does not necessarily need to be a prop named render