[TypeChallenges] 7. Readonly (easy)

문제

Implement the built-in Readonly<T> generic without using it.

Constructs a type with all properties of T set to readonly, meaning the properties of the constructed type cannot be reassigned.

 

For example:

interface Todo {
  title: string
  description: string
}

const todo: MyReadonly<Todo> = {
  title: "Hey",
  description: "foobar"
}

todo.title = "Hello" // Error: cannot reassign a readonly property
todo.description = "barFoo" // Error: cannot reassign a readonly property

(출처: https://github.com/type-challenges/type-challenges/blob/main/questions/00007-easy-readonly/README.md)

 

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나의 풀이

TypeScript의 내장 유틸리티 타입인 Readonly를 직접 구현하는 문제였다!

Readonly는 모든 프로퍼티가 읽기 전용으로 설정된 타입을 생성하므로 readonly 키워드를 이용해서 모든 프로퍼티를 읽기 전용으로 설정했다.

type MyReadonly<T> = {
  readonly [Key in keyof T]: T[Key]
}

 

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참고자료

1. 제네릭이란?

https://joshua1988.github.io/ts/guide/generics.html

제네릭 | 타입스크립트 핸드북

 

2. Readonly란?

https://www.typescriptlang.org/docs/handbook/utility-types.html#readonlytype

Documentation - Utility Types

 

2. readonly 키워드

https://www.typescriptlang.org/docs/handbook/2/objects.html#readonly-properties

Documentation - Object Types