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Flow，可选泛型是给定类型但未定义错误中缺少get属性

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有 TAction 这样的类型

export type TAction<TPayload = any> = {
  +type: string,
  payload?: TPayload
};

在这里我给它 TPayload

(
  state: TSettings,
  action: TAction<{ key: any, value: any }>
) => ({
    ...state,
    [action.payload.key]: action.payload.value
}),

然而，流程给我错误

Cannot get action.payload.key because property key is missing in undefined [1].
javascript flowtype

1 回答

  • 0

    您已将 payload 标记为maybe type（问号），因此可能是 null 或 undefined . 或

    删除问号：

    export type TAction<TPayload = any> = {
  +type: string,
  payload: TPayload
};

    或添加 payload 定义的检查，即：

    (
  state: TSettings,
  action: TAction<{ key: any, value: any }>
) => action.payload ? ({
    ...state,
    [action.payload.key]: action.payload.value
}) : {...state},
    回复于

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