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/Angular 7

FormControlDirective

directive

  • Syncs a standalone FormControl instance to a form control element.

See also

NgModule

Selectors

  • [formControl]

Properties

Property Description
viewModel: any

Internal reference to the view model value.

@Input('formControl')form: FormControl

Tracks the FormControl instance bound to the directive.

@Input('disabled')isDisabled: boolean Write-only.

Triggers a warning that this input should not be used with reactive forms.

@Input('ngModel')model: any
@Output('ngModelChange')update: EventEmitter
path: string[] Read-only.

Returns an array that represents the path from the top-level form to this control. Each index is the string name of the control on that level.

validator: ValidatorFn | null Read-only.

Synchronous validator function composed of all the synchronous validators registered with this directive.

asyncValidator: AsyncValidatorFn | null Read-only.

Async validator function composed of all the async validators registered with this directive.

control: FormControl Read-only.

The FormControl bound to this directive.

Inherited from NgControl

Inherited from AbstractControlDirective

Template variable references

Identifier Usage
ngForm #myTemplateVar="ngForm"

Description

Registering a single form control

The following examples shows how to register a standalone control and set its value.

import {Component} from '@angular/core';
import {FormControl, Validators} from '@angular/forms';

@Component({
  selector: 'example-app',
  template: `
     <input [formControl]="control">
      
     <p>Value: {{ control.value }}</p>
     <p>Validation status: {{ control.status }}</p>
     
     <button (click)="setValue()">Set value</button>
  `,
})
export class SimpleFormControl {
  control: FormControl = new FormControl('value', Validators.minLength(2));

  setValue() { this.control.setValue('new value'); }
}

Use with ngModel

Support for using the ngModel input property and ngModelChange event with reactive form directives has been deprecated in Angular v6 and will be removed in Angular v7.

Now deprecated:

<input [formControl]="control" [(ngModel)]="value">
this.value = 'some value';

This has been deprecated for a few reasons. First, developers have found this pattern confusing. It seems like the actual ngModel directive is being used, but in fact it's an input/output property named ngModel on the reactive form directive that simply approximates (some of) its behavior. Specifically, it allows getting/setting the value and intercepting value events. However, some of ngModel's other features - like delaying updates withngModelOptions or exporting the directive - simply don't work, which has understandably caused some confusion.

In addition, this pattern mixes template-driven and reactive forms strategies, which we generally don't recommend because it doesn't take advantage of the full benefits of either strategy. Setting the value in the template violates the template-agnostic principles behind reactive forms, whereas adding a FormControl/FormGroup layer in the class removes the convenience of defining forms in the template.

To update your code before v7, you'll want to decide whether to stick with reactive form directives (and get/set values using reactive forms patterns) or switch over to template-driven directives.

After (choice 1 - use reactive forms):

<input [formControl]="control">
this.control.setValue('some value');

After (choice 2 - use template-driven forms):

<input [(ngModel)]="value">
this.value = 'some value';

By default, when you use this pattern, you will see a deprecation warning once in dev mode. You can choose to silence this warning by providing a config for ReactiveFormsModule at import time:

imports: [
  ReactiveFormsModule.withConfig({warnOnNgModelWithFormControl: 'never'});
]

Alternatively, you can choose to surface a separate warning for each instance of this pattern with a config value of "always". This may help to track down where in the code the pattern is being used as the code is being updated.

Methods

A lifecycle method called when the directive's inputs change. For internal use only.

ngOnChanges(changes: SimpleChanges): void

Parameters
changes SimpleChanges

A object of key/value pairs for the set of changed inputs.

Returns

void

Sets the new value for the view model and emits an ngModelChange event.

viewToModelUpdate(newValue: any): void

Parameters
newValue any

The new value for the view model.

Returns

void

Inherited from NgControl

Inherited from AbstractControlDirective

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Licensed under the Creative Commons Attribution License 4.0.
https://v7.angular.io/api/forms/FormControlDirective