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

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 />
    }
  }

其他回答

如何:

mySwitchFunction = (param) => {
   switch (param) {
      case 'A':
         return ([
            <div />,
         ]);
      // etc...
   }
}
render() {
    return (
       <div>
          <div>
               // removed for brevity
          </div>

          { this.mySwitchFunction(param) }

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

这个助手应该可以做到这一点。 使用示例:

{componentSwitch(3, (switcher => switcher
    .case(1, () =>
        <p>It is one</p>
    )
    .case(2, () =>
        <p>It is two</p>
    )
    .default(() =>
        <p>It is something different</p>
    )
))}

助手:

interface SwitchCases<T> {
    case: (value: T, result: () => React.ReactNode) => SwitchCases<T>;
    default: (result: () => React.ReactNode) => SwitchCases<T>;
}

export function componentSwitch<T>(value: T, cases: (cases: SwitchCases<T>) => void) {

    var possibleCases: { value: T, result: () => React.ReactNode }[] = [];
    var defaultResult: (() => React.ReactNode) | null = null;

    var getSwitchCases: () => SwitchCases<T> = () => ({
        case: (value: T, result: () => React.ReactNode) => {
            possibleCases.push({ value: value, result });

            return getSwitchCases();
        },
        default: (result: () => React.ReactNode) => {
            defaultResult = result;

            return getSwitchCases();
        },
    })
    
    // getSwitchCases is recursive and will add all possible cases to the possibleCases array and sets defaultResult.
    cases(getSwitchCases());

    // Check if one of the cases is met
    for(const possibleCase of possibleCases) {
        if (possibleCase.value === value) {
            return possibleCase.result();
        }
    }

    // Check if the default case is defined
    if (defaultResult) {
        // Typescript wrongly assumes that defaultResult is always null.
        var fixedDefaultResult = defaultResult as (() => React.ReactNode);

        return fixedDefaultResult();
    }

    // None of the cases were met and default was not defined.
    return undefined;
}

下面是一个使用按钮在组件之间切换的完整工作示例

可以按如下方式设置构造函数

constructor(props)
{
    super(props);
    this.state={
        currentView: ''
    }
}

然后您就可以像下面这样渲染组件了

  render() 
{
    const switchView = () => {

    switch(this.state.currentView) 
    {

      case "settings":   return <h2>settings</h2>;
      case "dashboard":   return <h2>dashboard</h2>;

      default:      return <h2>dashboard</h2>
    }
  }

    return (

       <div>

            <button onClick={(e) => this.setState({currentView: "settings"})}>settings</button>
            <button onClick={(e) => this.setState({currentView: "dashboard"})}>dashboard</button>

            <div className="container">
                { switchView() }
            </div>


        </div>
    );
}

}

正如你所看到的,我正在使用一个按钮来切换状态。

我将接受的答案转换为箭头功能组件解决方案,看到James提供了类似的答案,可以得到未定义的错误。这就是解决方案:

  const renderSwitch = (param) => {
    switch (param) {
      case "foo":
        return "bar";
      default:
        return "foo";
    }
  };

  return (
    <div>
      <div></div>

      {renderSwitch(param)}

      <div></div>
    </div>
  );

React组件中的Switch-Case语句可以如下使用:

<div  id="time-list">
{   
    (() => {
        switch (groupByFilterId) {
            case 0:/*Case 0 */
                return (
                    <div>Case 0</div>
                )
               break;
           case 1: /*Case 1 */
           return ( 
            <div>Case 1</div>
            )
            break;
           case 2:/*Case 2 */
           return ( 
            <div>Case 2</div>
            )
            break;
        }
     })()}

      
       
    
    </div>