反應 HOC 類型推斷

Question

我想創建一個返回高階組件的高階函數。

在下面的示例中，我創建了一個validateSearchParams函數，該函數創建了一個可用於包裝組件的函數。 但是，Typescript (3.7.2) 無法正確推斷類型。

export function validateSearchParams<Props extends { location: Location }>(
  test: (searchParams: URLSearchParams) => boolean,
  redirectTo: string,
): (Cmp: React.ComponentType<Props>) => React.ComponentType<Props> {
  return (Cmp) => (props) => {
    const searchParams = new URLSearchParams(props.location.search);

    if (!test(searchParams)) {
      return <Redirect to={redirectTo} />;
    }

    return <Cmp {...props} />;
  };
}

export const Test: React.FC<{ something: boolean; location: Location }> = () => null;

// This is OK
validateSearchParams<{ something: boolean; location: Location }>(
  (searchParams) => !!searchParams.get('foo'),
  'hxxp://somewhere',
)(Test);

// ...but without an explicit type it does not compile
validateSearchParams((searchParams) => !!searchParams.get('foo'), 'http://test.example')(Test);
                                                                                         ^^^^

在最后一行中，我收到以下錯誤：

Argument of type 'FC<{ something: boolean; location: Location; }>' is not assignable to
parameter of type 'ComponentType<{ location: Location; }>'.
  Type 'FC<{ something: boolean; location: Location; }>' is not assignable to type
'FunctionComponent<{ location: Location; }>'.
    Types of parameters 'props' and 'props' are incompatible.
      Type 'PropsWithChildren<{ location: Location; }>' is not assignable to type
'PropsWithChildren<{ something: boolean; location: Location; }>'.
        Property 'something' is missing in type 'PropsWithChildren<{ location: Location; }>' but
required in type '{ something: boolean; location: Location; }'.ts(2345)

通過將Cmp合並到參數列表中，我還能夠創建一個更簡單的 HOC 版本：

export function validateSearchParams2<Props extends { location: Location; match: match<any> }>(
  Cmp: React.ComponentType<Props>,
  test: (searchParams: URLSearchParams) => boolean,
  redirectTo: string,
): React.ComponentType<Props> {
  return (props) => {
    const searchParams = new URLSearchParams(props.location.search);

    if (!test(searchParams)) {
      return <Redirect to={redirectTo} />;
    }

    return <Cmp {...props} />;
  };
}
export const Test: React.FC<{ something: boolean; location: Location }> = () => null;

validateSearchParams2(Test, (searchParams) => !!searchParams.get('foo'), 'hxxp://somewhere');

...但是有沒有辦法讓validateSearchParams的第一個版本在沒有顯式類型的情況下工作？

Answer 1

現在泛型類型Props設置在函數validateSearchParams 。 您想將泛型移動到返回的函數。 基本上validateSearchParams不是一個通用函數，但它返回一個通用 HOC。

export function validateSearchParams(
  test: (searchParams: URLSearchParams) => boolean,
  redirectTo: string,
): <Props extends { location: Location }>(Cmp: React.ComponentType<Props>) => React.ComponentType<Props> {
...

現在您不需要設置顯式類型，因為它可以從您調用它的組件中推斷出來。

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