angular-forms

What this skill does

# @angular/forms

**Version:** Angular 21 (2025)
**Tags:** Forms, Validation, Reactive Forms, Template-Driven

**References:** [Reactive Forms](https://angular.dev/guide/reactive-forms) • [Template-Driven](https://angular.dev/guide/forms) • [API](https://angular.io/api/forms)

## API Changes

This section documents recent version-specific API changes.

- NEW: Signal-based form controls — Angular 19+ signal integration for form controls

- NEW: Functional validators — Prefer functional validators over class-based validators

- NEW: `AbstractControl.markAllAsTouched()` — New method to mark all controls as touched

- NEW: `nonNullable` option — Create non-nullable FormControls

- NEW: Typed forms — Full TypeScript support for form groups and arrays

- DEPRECATED: Class-based validators — Migrate to functional validators

## Best Practices

- Use Reactive Forms for complex forms — Better structure, validation, and testability

```ts
import { FormBuilder, Validators, ReactiveFormsModule } from '@angular/forms';

@Component({
  standalone: true,
  imports: [ReactiveFormsModule],
  template: `
    <form [formGroup]="form" (ngSubmit)="onSubmit()">
      <input formControlName="email" />
      <div *ngIf="form.controls.email.invalid && form.controls.email.touched">
        Email is required
      </div>
    </form>
  `
})
export class LoginComponent {
  private fb = inject(FormBuilder);
  
  form = this.fb.nonNullable.group({
    email: ['', [Validators.required, Validators.email]],
    password: ['', [Validators.required, Validators.minLength(8)]]
  });

  onSubmit() {
    if (this.form.valid) {
      console.log(this.form.getRawValue());
    }
  }
}
```

- Use FormBuilder for cleaner code

```ts
form = this.fb.group({
  name: ['', Validators.required],
  email: ['', [Validators.required, Validators.email]],
  address: this.fb.group({
    street: [''],
    city: ['']
  })
});
```

- Use custom validators for complex logic

```ts
// Functional validator (preferred)
const forbiddenNameValidator = (control: AbstractControl): ValidationErrors | null => {
  const forbidden = ['admin', 'root', 'superuser'];
  return forbidden.includes(control.value) ? { forbiddenName: true } : null;
};

// Usage
name: ['', forbiddenNameValidator]
```

- Use async validators for server-side validation

```ts
email: ['', 
  [Validators.email], 
  [asyncValidator, { debounceTime: 300 }]
]
```

- Use FormArray for dynamic form fields

```ts
const form = this.fb.group({
  emails: this.fb.array([
    this.fb.control('')
  ])
});

get emails(): FormArray {
  return this.form.get('emails') as FormArray;
}

addEmail() {
  this.emails.push(this.fb.control(''));
}
```

- Use `updateOn` option for performance

```ts
// Only validate on blur
email: ['', { updateOn: 'blur' }]

// Only validate on submit
password: ['', { updateOn: 'submit' }]
```

- Show validation errors conditionally

```ts
<input formControlName="email" 
       [class.is-invalid]="email.invalid && (email.dirty || email.touched)" />
```

- Use disable() for conditionally disabled fields

```ts
// Disable based on another control
this.form.statusChanges.subscribe(() => {
  if (this.form.value.isAdmin) {
    this.form.controls.permissions.enable();
  } else {
    this.form.controls.permissions.disable();
  }
});
```

- Reset form properly

```ts
// Reset with default values
this.form.reset({ email: '', name: 'Default' });

// Reset and clear validators
this.form.reset();
this.form.clearValidators();
```