NgModel

What it does

Creates a FormControl instance from a domain model and binds it to a form control element.

The FormControl instance will track the value, user interaction, and validation status of the control and keep the view synced with the model. If used within a parent form, the directive will also register itself with the form as a child control.

How to use

This directive can be used by itself or as part of a larger form. All you need is the ngModel selector to activate it.

It accepts a domain model as an optional @Input. If you have a one-way binding to ngModel with [] syntax, changing the value of the domain model in the component class will set the value in the view. If you have a two-way binding with [()] syntax (also known as 'banana-box syntax'), the value in the UI will always be synced back to the domain model in your class as well.

If you wish to inspect the properties of the associated FormControl (like validity state), you can also export the directive into a local template variable using ngModel as the key (ex: #myVar="ngModel"). You can then access the control using the directive's control property, but most properties you'll need (like valid and dirty) will fall through to the control anyway, so you can access them directly. You can see a full list of properties directly available in AbstractControlDirective.

The following is an example of a simple standalone control using ngModel:

import {Component} from '@angular/core';

@Component({
  selector: 'example-app',
  template: `
    <input [(ngModel)]="name" #ctrl="ngModel" required>

    <p>Value: {{ name }}</p>
    <p>Valid: {{ ctrl.valid }}</p>

    <button (click)="setValue()">Set value</button>
  `,
})
export class SimpleNgModelComp {
  name: string = '';

  setValue() { this.name = 'Nancy'; }
}

When using the ngModel within <form> tags, you'll also need to supply a name attribute so that the control can be registered with the parent form under that name.

It's worth noting that in the context of a parent form, you often can skip one-way or two-way binding because the parent form will sync the value for you. You can access its properties by exporting it into a local template variable using ngForm (ex: #f="ngForm"). Then you can pass it where it needs to go on submit.

If you do need to populate initial values into your form, using a one-way binding for ngModel tends to be sufficient as long as you use the exported form's value rather than the domain model's value on submit.

Take a look at an example of using ngModel within a form:

import {Component} from '@angular/core';
import {NgForm} from '@angular/forms';

@Component({
  selector: 'example-app',
  template: `
    <form #f="ngForm" (ngSubmit)="onSubmit(f)" novalidate>
      <input name="first" ngModel required #first="ngModel">
      <input name="last" ngModel>
      <button>Submit</button>
    </form>

    <p>First name value: {{ first.value }}</p>
    <p>First name valid: {{ first.valid }}</p>
    <p>Form value: {{ f.value | json }}</p>
    <p>Form valid: {{ f.valid }}</p>
  `,
})
export class SimpleFormComp {
  onSubmit(f: NgForm) {
    console.log(f.value);  // { first: '', last: '' }
    console.log(f.valid);  // false
  }
}

npm package: @angular/forms

NgModule: FormsModule

Selectors

[ngModel]:not([formControlName]):not([formControl])

Exported as

ngModel

Class Description

Constructor

constructor(parent: ControlContainer, validators: Array<Validator|ValidatorFn>, asyncValidators: Array<Validator|AsyncValidatorFn>, valueAccessors: ControlValueAccessor[])