我有一个React组件,在组件的渲染方法中,我有这样的东西:

render() {
    return (
        <div>
            <div>
                // removed for brevity
            </div>

           { switch(...) {} }

            <div>
                // removed for brevity
            </div>
        </div>
    );
}

Now the point is that I have two div elements, one at the top and one at the bottom, that are fixed. In the middle I want to have a switch statement, and according to a value in my state I want to render a different component. So basically, I want the two div elements to be fixed always, and just in the middle to render a different component each time. I'm using this to implement a multi-step payment procedure). Though, as is the code currently it doesn't work, as it gives me an error saying that switch is unexpected. Any ideas how to achieve what I want?


当前回答

尽管这是另一种方法,但如果您已经完全使用了钩子,则可以利用useCallback来生成一个只在必要时重新创建的函数。

假设你有一个组件,它应该根据状态道具来呈现。使用钩子,你可以这样实现:

const MyComponent = ({ status }) => {
  const renderContent = React.useCallback(() => {
    switch(status) {
      case 'CONNECTING': 
        return <p className="connecting">Connecting...</p>;
      
      case 'CONNECTED': 
        return <p className="success">Connected Successfully!</p>

      default: 
        return null;
      
    }
  }, [status]);

  return (
    <div className="container">
      {renderContent()}
    </div>
  );
};

我喜欢这个是因为:

It's obvious what is going on - a function is created, and then later called (the immediately invoked anonymous function method looks a little odd, and can potentially confuse newer developers) The useCallback hook ensures that the renderContent callback is reused between renders, unless the depedency status changes The renderContent function uses a closure to access the necessary props passed in to the component. A separate function (like the accepted answer) requires the passing of the props into it, which can be burdensome (especially when using TypeScript, as the parameters should also be typed correctly)

其他回答

让它变得简单,只需使用许多if语句。

例如:

<Grid>
   {yourVar==="val1"&&(<> your code for val1 </>)}
   {yourVar==="val2"&&(<> your code for val2 </>)}
   .... other statments
</Grid>

试试这个,它也更干净:在一个函数中获得渲染的开关,并调用它传递你想要的参数。例如:

renderSwitch(param) {
  switch(param) {
    case 'foo':
      return 'bar';
    default:
      return 'foo';
  }
}

render() {
  return (
    <div>
      <div>
          // removed for brevity
      </div>
      {this.renderSwitch(param)}
      <div>
          // removed for brevity
      </div>
    </div>
  );
}

你可以这样做。

 <div>
          { object.map((item, index) => this.getComponent(item, index)) }
 </div>

getComponent(item, index) {
    switch (item.type) {
      case '1':
        return <Comp1/>
      case '2':
        return <Comp2/>
      case '3':
        return <Comp3 />
    }
  }

我知道我有点晚了,但我认为这个实现可能会有所帮助

您可以使用条件操作符来呈现组件

如果你有下面的switch语句

switch(value) {
    case CASE1:
        return <Case1Component/>

    case CASE2:
        return <Case2Component/>

    case CASE3:
        return <Case3Component/>

    default:
        return <DefaultComponent/>
}

你可以像这样把它转换成react组件

const cases = [CASE0, CASE1, CASE2]
// Reminds me of 'react-router-dom'
return (
    <div>
        {value === cases[0] && <Case0Component/>}
        {value === cases[1] && <Case1Component/>}
        {value === cases[2] && <Case2Component/>}
        {!cases.includes(value) && <DefaultComponent/>}
    </div>
)

我正在使用这个帮助器,它允许我在JSX中有开关语句

// in helpers folder const switchTrue = (object) => { const { default: defaultValue, ...rest } = object; const obj = { default: defaultValue, ...rest }; const result = Object.keys(obj).reduce((acc, cur) => { return { ...acc, [cur === 'default' ? 'true' : cur]: obj[cur], }; }, {}); return result['true']; }; const Sample = () => { const isDataLoading = false; return ( <div> { switchTrue({ [`${isDataLoading}`]: <div>Loading</div>, [`${!isDataLoading}`]: <div>Data Ready</div>, default: <div>Default</div>, }) } </div> ) } ReactDOM.render( <Sample/>, document.getElementById("react") ); <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script> <div id="react"></div>