跳到主要内容

Pick

介绍​

不使用 Pick<T, K> ，实现 TS 内置的 Pick<T, K> 的功能。

从类型 T 中选出符合 K 的属性，构造一个新的类型。

例如: 

ts
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
type MyPick<T, K> = any;
type TodoPreview = MyPick<Todo, 'title' | 'completed'>;
const todo: TodoPreview = {
  title: 'Clean room',
  completed: false,
};
ts
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
type MyPick<T, K> = any;
type TodoPreview = MyPick<Todo, 'title' | 'completed'>;
const todo: TodoPreview = {
  title: 'Clean room',
  completed: false,
};
View on GitHub

起点​

ts
/* _____________ Your Code Here _____________ */
type MyPick<T, K> = any;
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<Expected1, MyPick<Todo, 'title'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<Expected2, MyPick<Todo, 'title' | 'completed'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
    // @errors: 2344
  MyPick<Todo, 'title' | 'completed' | 'invalid'>
];
 
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
 
interface Expected1 {
  title: string;
}
 
interface Expected2 {
  title: string;
  completed: boolean;
}
ts
/* _____________ Your Code Here _____________ */
type MyPick<T, K> = any;
 
/* _____________ Test Cases _____________ */
type cases = [
  Expect<Equal<Expected1, MyPick<Todo, 'title'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
  Expect<Equal<Expected2, MyPick<Todo, 'title' | 'completed'>>>,
Type 'false' does not satisfy the constraint 'true'.2344Type 'false' does not satisfy the constraint 'true'.
    // @errors: 2344
  MyPick<Todo, 'title' | 'completed' | 'invalid'>
];
 
interface Todo {
  title: string;
  description: string;
  completed: boolean;
}
 
interface Expected1 {
  title: string;
}
 
interface Expected2 {
  title: string;
  completed: boolean;
}
Take the Challenge

解决方案​

点击展开答案
ts
type MyPick<T, K extends keyof T> = {
  [Key in K]: T[Key];
};
// 测试用例中的@ts-expect-error不会生效,所以会报错
type MyPick2<T,K> = {
  [P in keyof T as P extends K ? P : never]: T[P]
};
// 执行会报错, 和上面相同的原因
type MyPick3<T,K> = {
  [P in K & keyof T]: P extends T ? T[P] : never
};
ts
type MyPick<T, K extends keyof T> = {
  [Key in K]: T[Key];
};
// 测试用例中的@ts-expect-error不会生效,所以会报错
type MyPick2<T,K> = {
  [P in keyof T as P extends K ? P : never]: T[P]
};
// 执行会报错, 和上面相同的原因
type MyPick3<T,K> = {
  [P in K & keyof T]: P extends T ? T[P] : never
};
Checkout more Solutions