输入'元素| undefined' 不能分配给类型 'ReactElement<any, string | （（道具：任意）

Question

我有一个看起来像这样的组件。这个版本完美运行：

export default function StatusMessage(isAdded: boolean, errorMessage: string) {
  if (isAdded) {
    return <ResultAlert severity="success" text="User Added" />;
  } else {
    if (errorMessage !== '') {
      if (
        errorMessage.includes('email')
      ) {
        return <ResultAlert severity="error" />;
      }
      if (
        errorMessage.includes('phone number')
      ) {
        return (
          <ResultAlert severity="error" text="" />
        );
      } 
    }
  }
}

现在，我正在尝试更改导出它的方式。我正在尝试这个：

type StatusMessageProps = {
  isAdded: boolean; 
  errorMessage: string;
}

export const StatusMessage: React.FunctionComponent<StatusMessageProps> = ({
  isAdded,
  errorMessage
}) => {

但我不断收到错误消息：

Type '({ isAdded, errorMessage }: PropsWithChildren<StatusMessageProps>) => Element | undefined' is not assignable to type 'FunctionComponent<StatusMessageProps>'.
  Type 'Element | undefined' is not assignable to type 'ReactElement<any, string | ((props: any) => ReactElement<any, string | ... | (new (props: any) => Component<any, any, any>)> | null) | (new (props: any) => Component<any, any, any>)> | null'.
    Type 'undefined' is not assignable to type 'ReactElement<any, string | ((props: any) => ReactElement<any, string | ... | (new (props: any) => Component<any, any, any>)> | null) | (new (props: any) => Component<any, any, any>)> | null'.

I am using the same method on different pages but the error is only here

编辑：

我正在像这样使用这个组件：

 const [isAdded, setIsAdded] = useState(false);

{isSubmitted && StatusMessage(isAdded, errorMessage)}

它给了我一个关于 isAdded 的错误

Argument of type 'boolean' is not assignable to parameter of type 'PropsWithChildren<StatusMessageProps>'.ts(2345)

Answer 1

就我而言，我有一个身份验证包装器组件，如果身份验证正在加载或用户未经身份验证，则将返回加载页面组件，否则将返回子属性。

问题是我需要将子元素包裹在空的 html 标签中。

return <>{children}</>;

Answer 2

您一定忘记了在组件中返回值。您是否忘记 return null 因为 void 0 是 React 组件的不可接受的结果？

export const StatusMessage: React.FunctionComponent<StatusMessageProps> = ({
  isAdded,
  errorMessage
}) => {
  if (isAdded) {
    return <ResultAlert severity="success" text="User Added" />;
  } else {
    if (errorMessage !== '') {
      if (
        errorMessage.includes('email')
      ) {
        return <ResultAlert severity="error" />;
      }
      if (
        errorMessage.includes('phone number')
      ) {
        return (
          <ResultAlert severity="error" text="" />
        );
      } 
    }

    // Here where you missed
    return null;
  }
}

Answer 3

就我而言return null;不起作用，所以我return <></>;