「重学TS 2.0 」TS 练习题第四十六题

[semlinker]

实现 RequireAllOrNone 工具类型，用于满足以下功能。即当设置 age 属性时，gender 属性也会变成必填。具体的使用示例如下所示：

interface Person {
  name: string;
  age?: number;
  gender?: number;
}

type RequireAllOrNone<T, K extends keyof T> = // 你的实现代码

const p1: RequireAllOrNone<Person, 'age' | 'gender'> = {
  name: "lolo"
};

const p2: RequireAllOrNone<Person, 'age' | 'gender'> = {
  name: "lolo",
  age: 7,
  gender: 1
};

请在下面评论你的答案

[zhaoxiongfei]

interface Person {
  name: string;
  age?: number;
  gender?: number;
}

type RequireAllOrNone<T, K extends keyof T> = Omit<T, K> & (Required<Pick<T, K>> | Partial<Record<K, never>>)

const p1: RequireAllOrNone<Person, "age" | "gender"> = {
  name: "lolo"
};

const p2: RequireAllOrNone<Person, "age" | "gender"> = {
  name: "lolo",
  age: 7,
  gender: 1
};

const p3: RequireAllOrNone<Person, "age" | "gender"> = {
// const p3: SetRequired<Person, "age" | "gender"> = {
// const p3: Omit<Person, "age" | "gender"> = {
  name: "lolo",
  age: 7,
};

思路: 巧妙利用 never 和 可选。

[s1pz]

秒啊，但是有个问题啊，partial会把值变成 never | undefined ， 最终就是undefined。因此{
name: "lolo",
age: undefined
} 这样写也不会报错

[jackwangwj]

type RequireAllOrNone<T, K extends keyof T> = Omit<T, K> & ({
[P in K]-?: T[P]
} | {
[P in K]?: never
})

[dentm]

type Readonly<T> = {
     readonly [P in keyof T] -?: T[P]
  }

  type RequireAllOrNone<T, K extends keyof T> = Readonly<Pick<T, K>> & Omit<T, K>
···

[zhengyimeng]

type RequireAllOrNone<T, K extends keyof T> =
  | (Omit<T, K> & Required<Pick<T, K>>)
  | { [Key in keyof T]: Key extends K ? never: T[Key] };