Default values using Observables in Angular 2 Formbuilder

Question

Default values using Observables in Angular 2 Formbuilder

I am encountering an issue with setting the default value of an Angular 2 Form (formbuilder). In my case, the default values are observables retrieved from a server, so I am unable to implement them in the usual way:

export class UserComponent implements OnInit{

userForm: ControlGroup;
userData: any; // Initialize the observable variable

ngOnInit():any {

    this.userData = this._dataService.getAllData() // My Observable
        .subscribe(
            data => {
                this.userData = data;
            }
        );

    this.userForm = this._formBuilder.group({
                  // Setting the default value below
        'username': [this.userData.username, Validators.compose([ 
            this.usernameValid
        ])]
}

Does anyone have any suggestions on what changes need to be made? The form is currently not displaying anything inside the input fields...

forms typescript angular observable formbuilder

Answer 1

Answer №1

One approach to consider is dealing with the asynchronously loaded data. It's essential to ensure that form elements are updated once the response has been received.

ngOnInit():any {
  this.userData = this._dataService.getAllData()
    .subscribe(
      data => {
        this.userData = data;
        this.userForm.controls.username.updateValue(
                this.userData.username);
      }
    );

  this.userForm = this._formBuilder.group({
    'username': [this.userData.username, Validators.compose([ 
        this.usernameValid
    ])];
}

Answer 2

One approach to consider is dealing with the asynchronously loaded data. It's essential to ensure that form elements are updated once the response has been received.

ngOnInit():any {
  this.userData = this._dataService.getAllData()
    .subscribe(
      data => {
        this.userData = data;
        this.userForm.controls.username.updateValue(
                this.userData.username);
      }
    );

  this.userForm = this._formBuilder.group({
    'username': [this.userData.username, Validators.compose([ 
        this.usernameValid
    ])];
}

Answer 3

Answer №2

Another way to achieve this functionality is through the following method:

data: Observable<any>;

ngOnInit():any {

   this.data = this._dataService.getAllData();

   this.data
      .map((details) => {
         return this._formBuilder.group({
            username: [ this.data.username,
               Validators.compose([this.usernameValid])
            ]
      })
      .subscribe((userDetails) => {
         this.userDetails = userDetails
      })

}

To display this in your template, you can utilize the async pipe as demonstrated below:

<form *ngIf="data | async" [formGroup]="userDetails">
   //...//
</form>

This approach eliminates the need for calling updateValue(), making it simpler to manage multiple fields that require default values from observables.

Answer 4

Another way to achieve this functionality is through the following method:

data: Observable<any>;

ngOnInit():any {

   this.data = this._dataService.getAllData();

   this.data
      .map((details) => {
         return this._formBuilder.group({
            username: [ this.data.username,
               Validators.compose([this.usernameValid])
            ]
      })
      .subscribe((userDetails) => {
         this.userDetails = userDetails
      })

}

To display this in your template, you can utilize the async pipe as demonstrated below:

<form *ngIf="data | async" [formGroup]="userDetails">
   //...//
</form>

This approach eliminates the need for calling updateValue(), making it simpler to manage multiple fields that require default values from observables.

Default values using Observables in Angular 2 Formbuilder

Answer №1

Answer №2

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