Can you explain the distinction, if one exists, between a field value and a property within the context of TypeScript and Angular?

For this example, I am exploring two scenarios of a service that exposes an observable named test$. One case utilizes a getter to access the observable, while the other makes it available as a public field.

Do these approaches have any practical distinctions?

I have come across many instances of declarative programming using the field method. Is utilizing a getter not considered declarative in this context?

In the component:

@Component()
export const TestComp {
    private test$ = this.testService.test$; 
    constructor(private testService: TestService){}
}

Case 1: Service with field value:

@Injectable()
export const TestService {
    public test$ = of('test');
}

Case 2: Service with property/getter:

@Injectable()
export const TestService {

    private _test$ = of('test');
    public get test$() {
        return this._test$;
    }
}

Answer №1

Here are the benefits that I believe come with utilizing getters and setters:

  1. Implementing appropriate access specifiers and validation logic before retrieving an object's property.

  2. Avoiding an Anemic domain model, ensuring that classes defining the domain have their own logic and validations rather than relying on external services for all business logic.

To learn more about Anemic domain models, check out this link

Answer №2

In my opinion, the choice comes down to convenience and reducing repetitive code.

Take this scenario for instance:

interface Product{
  readonly name:String;
}

class ProductA implements Product {
  constructor(public readonly name:string){
  }
}

class ProductB implements Product {
  private _name:string;
  get name():string{
    return this.name;
  }
// + some way to set/mutate name internally - constructor/method
}

Both implementations correctly adhere to the Product interface, so from a consumer perspective, it doesn't matter which implementation is used. Therefore, in your situation, it ultimately boils down to the preference of the developer.

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