Stop receiving notifications from Angular valueChanges

Question

Stop receiving notifications from Angular valueChanges

In my service class, I have the following code snippet:

class UserFormService {
    createUserForm() {
        const userForm = new FormGroup({
            firstName: new FormControl(),
            lastName: new FormControl(),
            displayName: new FormControl()
        })

        userForm.controls.firstName.valueChanges.subscribe(firstName => {
            if(!userForm.value.displayName) {
                userForm.controls.displayName.setValue(`${firstName} additional text`)
            }
        })

        return userForm
    }
}

The createUserForm method is invoked in the component class. Do you think it is necessary to interrupt 'valueChanges' in the given code?

angular typescript angular-reactive-forms

Answer 1

Answer №1

I'm struggling to comprehend when a memory leak might occur in this scenario

Let's consider this example:

@Component({
  selector: 'app-user-test',
  standalone: true,
    imports: [CommonModule, ReactiveFormsModule],
  templateUrl: './user-test.component.html',
  styleUrls: ['./user-test.component.css']
})
export class UserTestComponent {

  constructor(private userFormService: UserFormService) { }

    form = this.userFormService.createUserForm()
}

If the 'form' object gets deleted, the subscription will be deleted as well

In the code snippet below (), it's important to unsubscribe because the injected route object holds a reference to the component object.

export class LoanDetailsPage implements OnInit, OnDestroy {
  id: number;
  private sub: any;

  constructor(private route: ActivatedRoute) {}

  ngOnInit() {
    this.sub = this.route.params.subscribe(params => {
       this.id = +params['id']; // (+) converts string 'id' to a number

       // In a real app: dispatch action to load the details here.
    });
  }

  ngOnDestroy() {
    this.sub.unsubscribe();
  }
}

Answer 2

I'm struggling to comprehend when a memory leak might occur in this scenario

Let's consider this example:

@Component({
  selector: 'app-user-test',
  standalone: true,
    imports: [CommonModule, ReactiveFormsModule],
  templateUrl: './user-test.component.html',
  styleUrls: ['./user-test.component.css']
})
export class UserTestComponent {

  constructor(private userFormService: UserFormService) { }

    form = this.userFormService.createUserForm()
}

If the 'form' object gets deleted, the subscription will be deleted as well

In the code snippet below (), it's important to unsubscribe because the injected route object holds a reference to the component object.

export class LoanDetailsPage implements OnInit, OnDestroy {
  id: number;
  private sub: any;

  constructor(private route: ActivatedRoute) {}

  ngOnInit() {
    this.sub = this.route.params.subscribe(params => {
       this.id = +params['id']; // (+) converts string 'id' to a number

       // In a real app: dispatch action to load the details here.
    });
  }

  ngOnDestroy() {
    this.sub.unsubscribe();
  }
}

Stop receiving notifications from Angular valueChanges

Answer №1

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