What is preventing the getters for form errors from functioning in my Angular Reactive Form component template, while a direct reference does work?

Question

What is preventing the getters for form errors from functioning in my Angular Reactive Form component template, while a direct reference does work?

I have a question regarding a small issue with an Angular reactive form in a lazily loaded signup module. The code structure is structured as follows:

TS

get email() {
  return this.myForm.get('email');
}
// While this code works from within the component, it does not work when referenced from within the template.

HTML

<div class="errors" *ngIf="email.errors?.required && email.touched">Please enter your email address</div>

In the template, the div is never displayed because the expression never evaluates to true, even when errors are present. I have double-checked in the console.

What's even more confusing is that I can easily use the getter in the component.ts file by writing console.log(this.email.errors), and it works perfectly fine there. However, it doesn't seem to work in the template.

To circumvent the issue, my messy solution has been to access the errors directly which surprisingly works:

<div class="errors" *ngIf="myForm.controls.email.errors.required && myForm.controls.email.touched">
  Please enter your email address
</div>
// This workaround works! But the expression is convoluted and lengthy.

Any assistance would be greatly appreciated!

angular typescript angular-reactive-forms angular-template-form

Answer 1

Answer №1

Have you ever used a template reference variable called #email in your input field, for example: <input #email ...>?

This could be the reason behind the issue you are facing. I have created a Stackblitz demo showcasing the error: https://stackblitz.com/edit/angular-qyt7kb

In this example, the firstName input has a template reference variable #firstName and the error div is not displayed. However, the lastName error div is shown correctly.

<form [formGroup]="form">

    <label>
      First Name:
      <input #firstName type="text" formControlName="firstName">
    </label>
    <div *ngIf="firstName.errors?.required && firstName.touched">*First Name is Required</div>

    <label>
      Last Name:
      <input type="text" formControlName="lastName">
    </label>
    <div *ngIf="lastName.errors?.required && lastName.touched">*Last Name is Required</div>

</form>

It appears that in the template, the template reference variable takes precedence over the getter with the same name in the TS file. The console.log statements display the errors accurately, as you mentioned.

Answer 2

Have you ever used a template reference variable called #email in your input field, for example: <input #email ...>?

This could be the reason behind the issue you are facing. I have created a Stackblitz demo showcasing the error: https://stackblitz.com/edit/angular-qyt7kb

In this example, the firstName input has a template reference variable #firstName and the error div is not displayed. However, the lastName error div is shown correctly.

<form [formGroup]="form">

    <label>
      First Name:
      <input #firstName type="text" formControlName="firstName">
    </label>
    <div *ngIf="firstName.errors?.required && firstName.touched">*First Name is Required</div>

    <label>
      Last Name:
      <input type="text" formControlName="lastName">
    </label>
    <div *ngIf="lastName.errors?.required && lastName.touched">*Last Name is Required</div>

</form>

It appears that in the template, the template reference variable takes precedence over the getter with the same name in the TS file. The console.log statements display the errors accurately, as you mentioned.

Answer 3

Answer №2

If you want to implement Reactive Forms, be sure to include the formGroup and formControlName directives in your template like so:

<form (ngSubmit)="submit()" [formGroup]="myForm">
    <label for="username">Username</label>
    <input type="text" id="username" formControlName="username">
    <span *ngIf="username.getError('required') &&
              (username.dirty || username.touched)">
      Username is required
    </span>

    <label for="password">Password</label>
    <input type="password" id="password" formControlName="password">
    <span *ngIf="myForm.get('password').getError('required') &&
              (myForm.get('password').dirty || myForm.get('password').touched)">
      Password is required
    </span>

    <input type="submit" value="Submit">
</form>

Next, create your FormGroup, define validators, and getter functions:

  myForm: FormGroup = new FormGroup({
    username: new FormControl('', Validators.required),
    password: new FormControl('', Validators.required),
  });

  get username() {
    return this.myForm.get('username');
  }

  get password() {
    return this.myForm.get('password');
  }

You can then use the getter functions for validation (like 'username' in the template) or directly reference them using

myForm.get('password').getError('required')

(similar to 'password' in the template).

To see a login example that demonstrates both methods of accessing errors in Reactive Forms with Angular, you can visit: https://stackblitz.com/edit/reactive-forms-get-errors

I hope this information is helpful!

Answer 4

If you want to implement Reactive Forms, be sure to include the formGroup and formControlName directives in your template like so:

<form (ngSubmit)="submit()" [formGroup]="myForm">
    <label for="username">Username</label>
    <input type="text" id="username" formControlName="username">
    <span *ngIf="username.getError('required') &&
              (username.dirty || username.touched)">
      Username is required
    </span>

    <label for="password">Password</label>
    <input type="password" id="password" formControlName="password">
    <span *ngIf="myForm.get('password').getError('required') &&
              (myForm.get('password').dirty || myForm.get('password').touched)">
      Password is required
    </span>

    <input type="submit" value="Submit">
</form>

Next, create your FormGroup, define validators, and getter functions:

  myForm: FormGroup = new FormGroup({
    username: new FormControl('', Validators.required),
    password: new FormControl('', Validators.required),
  });

  get username() {
    return this.myForm.get('username');
  }

  get password() {
    return this.myForm.get('password');
  }

You can then use the getter functions for validation (like 'username' in the template) or directly reference them using

myForm.get('password').getError('required')

(similar to 'password' in the template).

To see a login example that demonstrates both methods of accessing errors in Reactive Forms with Angular, you can visit: https://stackblitz.com/edit/reactive-forms-get-errors

I hope this information is helpful!

What is preventing the getters for form errors from functioning in my Angular Reactive Form component template, while a direct reference does work?

Answer №1

Answer №2

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