Typescript - 将子属性“链接”到父属性中的相同属性，因此当更新父属性时，它会更新子属性中的相同属性吗？

Question

A Company can have a Pia agreement, but doesn't need to have one. So, I have the following.ts classes to demonstrate this.

I just do this let submitObject = new Company(); and then I get a Company object with default null values that I can overwrite based on what's in my form.

When I set the "id" in the Company, I want it to also set the child (Pia) 's "companyId" using this same value. Is there a way to make it do this automatically, or do I need to manually do submitObject.pia.companyId = submitObject.id after every time I finish setting the values of a new Company object?

Company.ts

import { Pia } from "./Pia";

export class Company {
    id: number = null;
    name: string = null;
    address: string = null;
    authRequired: boolean = false;
    piaRequired: boolean = false;

    pia: Pia = new Pia;
}

Pia.ts

export class Pia {
    companyId: number = null;
    agreementNumber: string = null;
    effectiveDate: string = null;
    expirationDate: string = null;
}

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What I've tried:

Using extends / inheritance (I'm pretty sure I'm doing this incorrectly)

Company.ts

import { Pia } from "./Pia";

export class Company {
    constructor(public companyId: number) {
        this.id = companyId;
    }
    id: number = null;
    name: string = null;
    address: string = null;
    authRequired: boolean = false;
    piaRequired: boolean = false;
    pia: Pia = new Pia(this.companyId);
}

Pia.ts

import { Company } from "./Company";

export class Pia extends Company {

    // constructor(companyId: number) {
    //     super(companyId);
    // }

    // companyId: number = super.id;
    companyId: number = null;
    agreementNumber: string = null;
    effectiveDate: string = null;
    expirationDate: string = null;
}

Answer 1

You may use a getter/setter , although this may get out of hand if you have more properties you want to 'link':

 class Pia { companyId; constructor(id) { this.companyId = id } } class Company { pia; constructor(pia) { this.pia = pia } get id() { return this.pia.companyId } set id(id) { this.pia.companyId = id } } const c = new Company(new Pia(42)); // c.id += 27 // also works c.id = c.id + 27; // 'linked', inner object was also updated console.log(c.pia.companyId);

Note that it's not really 'linked', it's just that the Company's id member acts as a proxy between outside code and the inner Pia object's companyId .