说明
This directive accepts an existing FormGroup instance. It will then use this FormGroup instance to match any child FormControl, FormGroup, and FormArray instances to child FormControlName, FormGroupName, and FormArrayName directives.
Set value: You can set the form's initial value when instantiating the FormGroup, or you can set it programmatically later using the FormGroup's setValue or patchValue methods.
Listen to value: If you want to listen to changes in the value of the form, you can subscribe to the FormGroup's valueChanges event. You can also listen to its statusChanges event to be notified when the validation status is re-calculated.
Furthermore, you can listen to the directive's ngSubmit event to be notified when the user has triggered a form submission. The ngSubmit event will be emitted with the original form submission event.
Example
In this example, we create form controls for first name and last name.
import {Component} from '@angular/core'; import {FormControl, FormGroup, Validators} from '@angular/forms'; @Component({ selector: 'example-app', template: ` <form [formGroup]="form" (ngSubmit)="onSubmit()"> <div *ngIf="first.invalid"> Name is too short. </div> <input formControlName="first" placeholder="First name"> <input formControlName="last" placeholder="Last name"> <button type="submit">Submit</button> </form> <button (click)="setValue()">Set preset value</button> `, }) export class SimpleFormGroup { form = new FormGroup({ first: new FormControl('Nancy', Validators.minLength(2)), last: new FormControl('Drew'), }); get first(): any { return this.form.get('first'); } onSubmit(): void { console.log(this.form.value); // {first: 'Nancy', last: 'Drew'} } setValue() { this.form.setValue({first: 'Carson', last: 'Drew'}); } }npm package: @angular/forms
NgModule: ReactiveFormsModule
