DataClassWithInvariants.ts

class Address {

  private readonly addressLine1: string;
  private readonly addressLine2: string;
  private readonly city: string;
  private readonly state: string;
  private readonly country: string;
  private readonly postalCode: string;

  constructor(addressLine1: string, addressLine2: string, city: string, state: string, country: string, postalCode: string) {
    this.addressLine1 = addressLine1;
    this.addressLine2 = addressLine2;
    this.city = city;
    this.state = state;
    this.country = country;
    this.postalCode = postalCode;
  }

  getAddressLine1(): string {
    return this.addressLine1;
  }

  getAddressLine2(): string {
    return this.addressLine2;
  }

  getCity(): string {
    return this.city;
  }

  getState(): string {
    return this.state;
  }

  getCountry(): string {
    return this.country;
  }

  getPostalCode(): string {
    return this.postalCode;
  }
}

class Child {
    private age: number;

    constructor(age: number) {
        this.age = age;
    }

    getAge(): number {
        return this.age;
    }

    setAge(age: number): void {
        this.age = age;
    }
}


class Child {
    private age: number;

    static makeBaby(): Child {
        return new Child(0);
    }

    constructor(age: number) {
        if (age >= 4) {
            throw new Error("Not a child!");
        }
        this.age = age;
    }

    getAge(): number {
        return this.age;
    }

    setAge(age: number): void {
        this.age = age;
    }
}