[TypeScript] Type Challenges #2793 - Mutable

题目描述

实现一个通用的类型Mutable<T>，使类型T的全部属性可变（非只读）。

例如：

interface Todo {
  readonly title: string
  readonly description: string
  readonly completed: boolean
}

type MutableTodo = Mutable<Todo> // { title: string; description: string; completed: boolean; }

题解

// ============= Test Cases =============
import type { Equal, Expect } from './test-utils'

interface Todo1 {
  title: string
  description: string
  completed: boolean
  meta: {
    author: string
  }
}

type List = [1, 2, 3]

type cases = [
  Expect<Equal<Mutable<Readonly<Todo1>>, Todo1>>,
  Expect<Equal<Mutable<Readonly<List>>, List>>,
]

type errors = [
  // @ts-expect-error
  Mutable<'string'>,
  // @ts-expect-error
  Mutable<0>,
]


// ============= Your Code Here =============
type Mutable<T extends Record<string, any>> = {
  -readonly [K in keyof T]: T[K]
}

映射类型

type Mutable<T extends Record<string, any>> = {
  -readonly [P in keyof T]: T[P]
}

• 类型约束：

  • T extends Record<string, any>：确保T是一个对象类型，其键为字符串，值为任意类型

• 映射类型：

  • -readonly [P in keyof T]: T[P]：

    • -readonly：移除readonly修饰符，使属性变为可变

    • [P in keyof T]：遍历T的所有键

    • T[P]：保留每个键的值类型