如何在React组件中使用switch语句?

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

我在render()方法中做了这个:

  render() {
    const project = () => {
      switch(this.projectName) {

        case "one":   return <ComponentA />;
        case "two":   return <ComponentB />;
        case "three": return <ComponentC />;
        case "four":  return <ComponentD />;

        default:      return <h1>No project match</h1>
      }
    }

    return (
      <div>{ project() }</div>
    )
  }

我试图保持render()返回干净，所以我把我的逻辑放在一个'const'函数上面。这样我也可以缩进我的开关盒整齐。

2018-10-03 02:21:51

其他回答

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>
  );
}

2017-10-05 19:02:01

我在render()方法中做了这个:

  render() {
    const project = () => {
      switch(this.projectName) {

        case "one":   return <ComponentA />;
        case "two":   return <ComponentB />;
        case "three": return <ComponentC />;
        case "four":  return <ComponentD />;

        default:      return <h1>No project match</h1>
      }
    }

    return (
      <div>{ project() }</div>
    )
  }

我试图保持render()返回干净，所以我把我的逻辑放在一个'const'函数上面。这样我也可以缩进我的开关盒整齐。

2018-10-03 02:21:51

改进了一点马特·韦的回答。

export const Switch = ({ test, children }) => { const defaultResult = children.find((child) => child.props.default) || null; const result = children.find((child) => child.props.value === test); return result || defaultResult; }; export const Case = ({ children }) => children; const color = getColorFromTheMostComplexFnEver(); <Switch test={color}> <Case value="Green">Forest</Case> <Case value="Red">Blood</Case> <Case default>Predator</Case> </Switch> <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>

2022-10-05 10:11:14

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>
)

2021-06-21 13:46:00

我不太喜欢当前的任何答案，因为它们要么太啰嗦，要么需要您在代码中跳跃才能理解发生了什么。

我更喜欢用一个更以react组件为中心的方式来做这件事，通过创建一个<Switch/>。这个组件的任务是获取一个道具，并且只呈现子道具与该道具匹配的子元素。所以在下面的例子中，我在开关上创建了一个测试道具，并将其与子节点上的值道具进行比较，只渲染匹配的值道具。

例子:

const Switch = props => { const { test, children } = props // filter out only children with a matching prop return children.find(child => { return child.props.value === test }) } const Sample = props => { const someTest = true return ( <Switch test={someTest}> <div value={false}>Will display if someTest is false</div> <div value={true}>Will display if someTest is true</div> </Switch> ) } 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>

您可以根据自己的需要进行简单或复杂的切换。不要忘记对子节点及其值道具执行更健壮的检查。

2020-02-20 05:40:18

如何在React组件中使用switch语句?

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