如何在 TypeScript 中创建 RequireOnlyOne 嵌套类型？

Question

我经常看到这个代码片段：

type RequireOnlyOne<T, Keys extends keyof T = keyof T> =
Pick<T, Exclude<keyof T, Keys>>
& {
    [K in Keys]-?:
        Required<Pick<T, K>>
        & Partial<Record<Exclude<Keys, K>, undefined>>
}[Keys]

在这里你可以找到我提出的问题。

它有效，但是，我有这样的结构：

export interface MenuItems {
  firstLevel: {
    secondLevel: ['one', 'two']
  };
  anotherFirstLevel: {
    anotherSecondLevel: ['one', 'two'],
    oneMoreSecondLevel: null
  };
}

我需要为第一级和第二级应用RequireOnlyOne ，但我无法确定RequireOnlyOne类型的更改内容，因此它适用于每个 firstLevel 键，但也适用于 secondLevel 键。 就像现在一样，我只能选择一个 firstLevel，但可以选择该 firstLevel 的多个 secondLevel。

我还尝试用一个对象组合一个新类型，该对象的键可以是RequireOnlyOne<keyof MenuItems>和一个也使用RequireOnlyOne作为值的值，但无法实现。

我想要的示例，将所需类型称为customType ：

const workingObject: customType = {
  firstLevel: { // Just one property of the first level
    secondLevel: ['one', 'two'] // Just one property of the second level
  };
}

const errorObject: customType = {
  firstLevel: {
    secondLevel: ['one', 'two']
  };
  anotherFirstLevel: { // Should not work as I am including 2 properties for the first level
    anotherSecondLevel: ['one', 'two']
  };
}

const anotherErrorObject: customType = {
  anotherFirstLevel: {
    anotherSecondLevel: ['one', 'two'],
    oneMoreSecondLevel: null // Should not work neither as I am including 2 properties for second level
  };
}

如果对象具有多个第一级属性和/或多个第二级属性，则该类型应引发错误。 使用建议的RequireOnlyOne类型，我可以实现这一点，但仅适用于第一级，但我需要第一级和第二级的相同效果。

有任何想法吗？

Answer 1

IMO 这是一个非常复杂的问题，我建议寻找替代方案并重构代码。

否则，您可能会发现这很有帮助：

type RequireOnlyOneUnion<T, Keys extends KeysOfUnion<T> = KeysOfUnion<T>> = Pick<T, Exclude<keyof T, Keys>> &
  {
    [K in Keys]-?: Required<Pick<T, K>> & Partial<Record<Exclude<Keys, K>, undefined>>;
  }[Keys];

export interface MenuItems {
  firstLevel: {
    secondLevel: ["one", "two"];
  };
  anotherFirstLevel: {
    anotherSecondLevel: ["one", "two"];
    oneMoreSecondLevel: null;
  };
}

type KeysOfUnion<T> = T extends T ? keyof T : never;

// ok
const a: RequireOnlyOneUnion<MenuItems[keyof typeof x], KeysOfUnion<MenuItems[keyof typeof x]>> = {
  anotherSecondLevel: ["one", "two"],
};
// error
const b: RequireOnlyOneUnion<MenuItems[keyof typeof x], KeysOfUnion<MenuItems[keyof typeof x]>> = {
  secondLevel: ["one", "two"],
  anotherSecondLevel: ["one", "two"],
};

Answer 2

我不知道如何更改RequireOnlyOne类型，但我知道如何创建新类型。

export interface MenuItems {
  firstLevel: {
    secondLevel: ['one', 'two']
  };
  anotherFirstLevel: {
    anotherSecondLevel: ['one', 'two']
    oneMoreSecondLevel: null
  };
}

type Primitives = string | number | boolean | null | undefined | bigint | symbol

type UnionKeys<T> = T extends T ? keyof T : never;
// credits goes to https://stackoverflow.com/questions/65805600/type-union-not-checking-for-excess-properties#answer-65805753
type StrictUnionHelper<T, TAll> =
  T extends any
  ? T & Partial<Record<Exclude<UnionKeys<TAll>, keyof T>, never>> : never;

type StrictUnion<T> = StrictUnionHelper<T, T>

type Transform<Obj, Keys extends keyof Obj = keyof Obj, Result = never> =
  StrictUnion<
    Keys extends string ? { // #1
      [Key in Keys]:
      Key extends keyof Obj
      ? (Obj[Key] extends Primitives
        ? Obj[Key]
        : (Obj[Key] extends any[]
          ? Obj[Key]
          : Transform<Obj[Key], keyof Obj[Key], Obj[Key]>)
      )
      : never
    } : Result>


type CustomType = Transform<MenuItems>

const workingObject: CustomType = {
  firstLevel: { // Just one property of the first level
    secondLevel: ['one', 'two'] // Just one property of the second level
  },
}


const errorObject: CustomType = {
  firstLevel: {
    secondLevel: ['one', 'two']
  },
  anotherFirstLevel: { // Should not work as I am including 2 properties for the first level
    anotherSecondLevel: ['one', 'two']
  },
}

const anotherErrorObject: CustomType= {
  anotherFirstLevel: {
    anotherSecondLevel: ['one', 'two'],
    oneMoreSecondLevel: null // Should not work neither as I am including 2 properties for second level
  },
}

Transform - 是一种主要的实用程序类型。 递归迭代键。 1# Keys extends string - 这一行确保Keys is distributet 。 这意味着该行之后的整个代码将应用于每个键。 请参阅文档了解更多信息。

我还添加了Obj[Key] extends any[] - 因为你不想（我想）遍历数组键。

操场