TypeScript Mapped TypesTypeScript 매핑 타입

type Readonly<T> = {
  readonly [K in keyof T]: T[K];
};

type Partial<T> = {
  [K in keyof T]?: T[K];
};

interface User { id: number; name: string; }
type ReadonlyUser = Readonly<User>;
// { readonly id: number; readonly name: string; }

// -readonly: readonly 제거
type Mutable<T> = {
  -readonly [K in keyof T]: T[K];
};

// -?: 선택적 제거 (Required와 동일)
type Required<T> = {
  [K in keyof T]-?: T[K];
};

// 키를 변환
type Getters<T> = {
  [K in keyof T as `get${Capitalize<string & K>}`]: () => T[K];
};

interface Person { name: string; age: number; }
type PersonGetters = Getters<Person>;
// { getName: () => string; getAge: () => number; }

// 키 필터링 (never로 제거)
type NonFunctionKeys<T> = {
  [K in keyof T as T[K] extends Function ? never : K]: T[K];
};

// 값 타입 변환
type Nullable<T> = {
  [K in keyof T]: T[K] | null;
};

// 중첩 구조 처리
type DeepPartial<T> = {
  [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K];
};

interface Config {
  server: { host: string; port: number };
  debug: boolean;
}
type PartialConfig = DeepPartial<Config>;
// server?: { host?: string; port?: number }; debug?: boolean;