Angular 5 multiple input validation

Question

I am trying to make a custom validation so i have created the following directive:

import {Directive, Input} from '@angular/core';
import {AbstractControl, NG_VALIDATORS, Validator} from '@angular/forms';
@Directive({
    selector: '[appEqualValidator]',
    providers: [
        {provide: NG_VALIDATORS, useExisting: EqualValidatorDirective, multi: true}
    ]
})
export class EqualValidatorDirective implements Validator {
    @Input('inputOne')
    inputOne: string;
    @Input('inputTwo')
    inputTwo: string;

    constructor() {
    }

    validate(c: AbstractControl) {

        const value = c.value;
        if ((value == null || value === undefined || value === '') && this.inputOne === this.inputTwo) {
            return {
                equalTo: {condition: this.inputOne === this.inputTwo}
            };
        }
        return null;
    }
}

Now I am trying to add this to my form however I am having some issues using the multiple inputs:

 <div class="form-group">
    <label>E-mail</label>
    <input type="email" class="form-control" placeholder="Indtast email" [(ngModel)]="model.email" name="email" [email]="true" required/>
</div>
<div class="form-group">
    <label style="display: block">Gentag E-mail</label>
    <input type="email" class="form-control" placeholder="Gentag email" [(ngModel)]="model.emailRepeat" required [email]="true" 
[appEqualValidator]="value" name="emailRepeat"/>
    <li *ngIf="!emailVerify">
        De to emails er ikke ens
    </li>
</div>

I am not sure how to use the directive within the form. and making sure i can get both inputs.

I was hoping some of you could point me in the right direction.

Have you considered using Reactive Forms? Angular has validators that you can implement without much hassle. See here: angular.io/guide/form-validation — IvanS95
– IvanS95, Commented Oct 30, 2018 at 21:20
@IvanS95 Does this have an equal to where you can match two input fields? — Marc Rasmussen
– Marc Rasmussen, Commented Oct 30, 2018 at 21:44

DeborahK · Accepted Answer · 2018-10-30 22:22:39Z

I did something similar with reactive forms.

Here is the validator:

function emailMatcher(c: AbstractControl): { [key: string]: boolean } | null {
  const emailControl = c.get('email');
  const confirmControl = c.get('confirmEmail');

  if (emailControl.pristine || confirmControl.pristine) {
    return null;
  }

  if (emailControl.value === confirmControl.value) {
    return null;
  }
  return { 'match': true };
}

Here is the formbuilder:

this.customerForm = this.fb.group({
  firstName: ['', [Validators.required, Validators.minLength(3)]],
  lastName: ['', [Validators.required, Validators.maxLength(50)]],
  emailGroup: this.fb.group({
    email: ['', [Validators.required, Validators.email]],
    confirmEmail: ['', Validators.required],
  }, { validator: emailMatcher }),
  phone: ''
});

Here is the HTML:

<div class="form-group row">
  <label class="col-md-2 col-form-label"
         for="emailId">Email</label>
  <div class="col-md-8">
    <input class="form-control"
           id="emailId"
           type="email"
           placeholder="Email (required)"
           formControlName="email"
           [ngClass]="{'is-invalid': customerForm.get('emailGroup').errors ||
                                      ((customerForm.get('emailGroup.email').touched || 
                                      customerForm.get('emailGroup.email').dirty) && 
                                      !customerForm.get('emailGroup.email').valid) }" />
    <span class="invalid-feedback">
      <span *ngIf="customerForm.get('emailGroup.email').errors?.required">
        Please enter your email address.
      </span>
      <span *ngIf="customerForm.get('emailGroup.email').errors?.email">
        Please enter a valid email address.
      </span>
    </span>
  </div>
</div>

<div class="form-group row">
  <label class="col-md-2 col-form-label"
         for="confirmEmailId">Confirm Email</label>
  <div class="col-md-8">
    <input class="form-control"
           id="confirmEmailId"
           type="email"
           placeholder="Confirm Email (required)"
           formControlName="confirmEmail"
           [ngClass]="{'is-invalid': customerForm.get('emailGroup').errors ||
                                     ((customerForm.get('emailGroup.confirmEmail').touched || 
                                      customerForm.get('emailGroup.confirmEmail').dirty) && 
                                      !customerForm.get('emailGroup.confirmEmail').valid) }" />
    <span class="invalid-feedback">
      <span *ngIf="customerForm.get('emailGroup.confirmEmail').errors?.required">
        Please confirm your email address.
      </span>
      <span *ngIf="customerForm.get('emailGroup').errors?.match">
        The confirmation does not match the email address.
      </span>
    </span>
  </div>
</div>

You can find the complete solution here:

https://github.com/DeborahK/Angular-ReactiveForms/tree/master/Demo-Final-Updated/src/app/customers

Rafael · Accepted Answer · 2018-10-30 21:29:00Z

1

You can do this wrapping both inputs in an NgModelGroup. It extends AbstractControlDirective, so it may take validators.

<div ngModelGroup="emails" #emails="ngModelGroup" [appEqualValidator]="value">
    <div class="form-group">
        <label>E-mail</label>
        <input type="email" class="form-control" placeholder="Indtast email" [(ngModel)]="model.email" name="email" [email]="true" required/>
    </div>
    <div class="form-group">
        <label style="display: block">Gentag E-mail</label>
        <input type="email" class="form-control" placeholder="Gentag email" [(ngModel)]="model.emailRepeat" required [email]="true" name="emailRepeat"/>
        <li *ngIf="!emailVerify">De to emails er ikke ens</li>
    </div>
</div>

Whenever a child control changes, the group validator will be called. In validate(), you will need to cast to a FormGroup and input value equality.

1 Comment

Marc Rasmussen Over a year ago

Hey mate when i try this i get : Can't bind to 'appEqualValidator' since it isn't a known property of 'div'

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