Guide to configure Validator to reject the selection of the first index option in Angular 2

When using a select option, it should be set up like:

<div class="form-group row" [ngClass]="{'has-error': (!form.controls['blockFirstIndex'].valid && form.controls['blockFirstIndex'].touched), 'has-success': (form.controls['blockFirstIndex'].valid && form.controls['blockFirstIndex'].touched)}">
      <label class="col-sm-3 control-label">blockFirstIndex</label>
      <div class="col-sm-9">
            <select formControlName="blockFirstIndex" [(ngModel)]="value" class="form-control">
                 <option *ngFor="let item of items" [disabled]="item.id==0" [ngValue]="item">{{item.name}}</option>
            </select>
      </div>
</div>

To set up a validator, use the following code:

this.form = this.fb.group({
    'blockFirstIndex': ['', Validators.compose([Validators.required])],
});

If you want the validator to not accept the select option with index 0, how should I go about doing that?

angulartypescript

Answer №1

A potential form controller implementation could resemble the following structure:

firstIndexControl: new FormControl("", [
                    SelectionValidator.isValidSelection,
                    Validators.required
                ])

Additionally, you can create a custom validator like this:

import {FormControl} from '@angular/forms'; 
    export class SelectionValidator {
       static  isValidSelection(control: FormControl){
            if (control.value === "" || control.value=== "0") {
                return { "Please provide a valid selection": true };
            }
            return null;
        }

    }

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