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RequiredByKeys

介绍​

实现一个通用的RequiredByKeys<T, K>，它接收两个类型参数T和K。

K指定应设为必选的T的属性集。当没有提供K时，它就和普通的Required<T>一样使所有的属性成为必选的。

ts
interface User {
  name?: string
  age?: number
  address?: string
}
type UserRequiredName = RequiredByKeys<User, 'name'> // { name: string; age?: number; address?: string }
ts
interface User {
  name?: string
  age?: number
  address?: string
}
type UserRequiredName = RequiredByKeys<User, 'name'> // { name: string; age?: number; address?: string }
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起点​

ts
/* _____________ Your Code Here _____________ */
 
type RequiredByKeys<T, K> = any
 
/* _____________ Test Cases _____________ */
 
interface User {
  name?: string
  age?: number
  address?: string
}
 
interface UserRequiredName {
  name: string
  age?: number
  address?: string
}
 
interface UserRequiredNameAndAge {
  name: string
  age: number
  address?: string
}
 
type cases = [
  Expect<Equal<RequiredByKeys<User, 'name'>, UserRequiredName>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<RequiredByKeys<User, 'name' | 'age'>, UserRequiredNameAndAge>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<RequiredByKeys<User>, Required<User>>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'RequiredByKeys' requires 2 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'RequiredByKeys' requires 2 type argument(s).
  // @ts-expect-error
  Expect<Equal<RequiredByKeys<User, 'name' | 'unknown'>, UserRequiredName>>,
]
 
ts
/* _____________ Your Code Here _____________ */
 
type RequiredByKeys<T, K> = any
 
/* _____________ Test Cases _____________ */
 
interface User {
  name?: string
  age?: number
  address?: string
}
 
interface UserRequiredName {
  name: string
  age?: number
  address?: string
}
 
interface UserRequiredNameAndAge {
  name: string
  age: number
  address?: string
}
 
type cases = [
  Expect<Equal<RequiredByKeys<User, 'name'>, UserRequiredName>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<RequiredByKeys<User, 'name' | 'age'>, UserRequiredNameAndAge>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<RequiredByKeys<User>, Required<User>>>,
Type 'false' does not satisfy the constraint 'true'.
Generic type 'RequiredByKeys' requires 2 type argument(s).2344
2314Type 'false' does not satisfy the constraint 'true'.
Generic type 'RequiredByKeys' requires 2 type argument(s).
  // @ts-expect-error
  Expect<Equal<RequiredByKeys<User, 'name' | 'unknown'>, UserRequiredName>>,
]
 
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解决方案​

Spoiler warning // Click to reveal answer
ts
// most popular 
type RequiredByKeys<
  T, 
  K extends keyof T = keyof T,
  O = Omit<T, K> & { [P in K]-?: T[P] }
> = { [P in keyof O]: O[P] }
 
 
ts
// most popular 
type RequiredByKeys<
  T, 
  K extends keyof T = keyof T,
  O = Omit<T, K> & { [P in K]-?: T[P] }
> = { [P in keyof O]: O[P] }
 
 
ts
// 按照PartialByKeys的思路
type RequiredByKeys<T, K extends keyof T = keyof T> =Omit< {
  [P in keyof T as P extends K ? P : never]-?: T[P]
} & Omit<T, K>, never>
 
ts
// 按照PartialByKeys的思路
type RequiredByKeys<T, K extends keyof T = keyof T> =Omit< {
  [P in keyof T as P extends K ? P : never]-?: T[P]
} & Omit<T, K>, never>
 
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