Angular form validation hint printing-CodePudding

i am building a form in angular, and i'm using validators for each field, the html form looks like this :

<form [formGroup]="form">
      <mat-form-field>
        <label translate>Name field</label>
        <input formControlName="name" matInput>
      </mat-form-field>
...

And in the .ts file i initialize the form with:

ngOnInit() {
    this.initializeForm();
  }

  initializeForm() {
    this.form = this.fb.group({
      nameControl: new FormControl(this.initialShare?.name, [Validators.required, noWhitespaceValidator]),
      ...
    });
  }

noWhitespaceValidator is a custom validator that checks if the user input consists of only whitespaces.

My question is, how could i add a piece of text that shows which validator does not pass, for example, i want to print: Name is required, if the Validators.required fails, or , Name cannot be composed of only whitespaces, if the noWhitespaceValidator fails.

CodePudding user response：

if you are using Material Inputs you can show your errors using mat-error

Like This

 <mat-form-field>
        <label translate>Name field</label>
        <input formControlName="nameControl" matInput>
        <mat-error *ngIf="form.get('nameControl').hasError('required')">Name is required</mat-error>
        <mat-error *ngIf="form.get('nameControl').hasError('THE_ERROR_NAME_THAT_IS_RETURNING_FROM_VALIDATOR')"> Name cannot be composed of only whitespaces</mat-error>
 </mat-form-field>

PLEASE NOTE:THE_ERROR_NAME_THAT_IS_RETURNING_FROM_VALIDATOR field should be replaced with the key which is returning from noWhitespaceValidator validator

CodePudding user response：

It's like @iLuvLogix said in comments

<div *ngIf="form.controls['nameControl'].errors.noWhitespaceValidator >
   Name cannot be composed of only whitespaces
</div>            
<div *ngIf="form.controls['nameControl'].errors.required">
         Name is required
</div>

see this link: https://angular.io/guide/form-validation