TvI 2

extendsAndImplements.ts

type TBase = {
  t: number;
};

interface IBase {
  i: number;
}

// extends 사용
interface I1 extends TBase {}

interface I2 extends IBase {}

// implements 사용
class C1 implements TBase {
  constructor(public t: number) {}
}

class C2 implements IBase {
  constructor(public i: number) {}
}

// 곱 타입에 대한 extends, implements 사용
type TIntersection = TBase & {
  t2: number;
};

interface I3 extends TIntersection {}

class C3 implements TIntersection {
  constructor(public t: number, public t2: number) {}
}

interface I4 extends I3 {}

class C4 implements I3 {
  constructor(public t: number, public t2: number) {}
}

// 오류: 합 타입에 대한 extends, implements 사용
type TUnion = TBase | {
  u: number;
};

interface I5 extends TUnion {}
// error(TS2312)
// An interface can only extend an object type
// or intersection of object types with statically known members.

class C5 implements TUnion {}
// error(TS2422)
// A class can only implement an object type
// or intersection of object types with statically known members.