ProductA.ts

export interface AbstractProductA {
  usefulFunctionA(): string;
}

export class ConcreteProductA1 implements AbstractProductA {
  public usefulFunctionA(): string {
    return "The result of the product A1.";
  }
}

export class ConcreteProductA2 implements AbstractProductA {
  public usefulFunctionA(): string {
    return "The result of the product A2.";
  }
}