Angular中响应式表单的三种更新值方法详析

@Component({
 selector: 'app-validation',
 template: `
 <form [formGroup]="form" (ngSubmit)="_submitForm(form)">
 <input type="email" formControlName="email">
 <input type="text" formControlName="nickname">
 <button type="submit" [disabled]="form.invalid">Submit</button>
 </form>
 `
})
export class UserEditComponent {
 constructor(private fb: FormBuilder, private route: ActivatedRoute) {}
 
 ngOnInit() {
 this.form = this.fb.group({
  email: ['', Validators.compose([Validators.required, Validators.email])],
  nickname: ['', [Validators.required]]
 });
 
 this.route.params
  .switchMap((params: Params) => loadUser(+params['id']))
  .subscribe(data => {
  // Updating value
  });
 }
 
 loadUser() {
 return Observable.of({ email: 'xx@xx.com', nickname: 'cipchk' }).delay(1000);
 }
 
 _submitForm({ value }) {
 // Save value
 }
}

this.form = this.fb.group({
 email: ['', Validators.compose([Validators.required, Validators.email])],
 nickname: ['', [Validators.required]]
});

this.form.patchValue({ nickname: 'cipchk' });

patchValue(value: {[key: string]: any}, options: {onlySelf?: boolean, emitEvent?: boolean} = {}): void {
 Object.keys(value).forEach(name => {
 if (this.controls[name]) {
 this.controls[name].patchValue(value[name], {onlySelf: true, emitEvent: options.emitEvent});
 }
 });
 this.updateValueAndValidity(options);
}

Object.keys({ nickname: 'cipchk' }).forEach(name => { 
 console.log(name); 
});
// [ 'nickname' ]

this.controls[name].patchValue(value[name], {onlySelf: true, emitEvent: options.emitEvent});

setValue(value: {[key: string]: any}, options: {onlySelf?: boolean, emitEvent?: boolean} = {}): void {
 this._checkAllValuesPresent(value);
 Object.keys(value).forEach(name => {
 this._throwIfControlMissing(name);
 this.controls[name].setValue(value[name], {onlySelf: true, emitEvent: options.emitEvent});
 });
 this.updateValueAndValidity(options);
}

_throwIfControlMissing(name: string): void {
 if (!Object.keys(this.controls).length) {
 throw new Error(`
 There are no form controls registered with this group yet. If you're using ngModel,
 you may want to check next tick (e.g. use setTimeout).
 `);
 }
 if (!this.controls[name]) {
 throw new Error(`Cannot find form control with name: ${name}.`);
 }
}

reset(formState: any = null, options: {onlySelf?: boolean, emitEvent?: boolean} = {}): void {
 this._applyFormState(formState);
 this.markAsPristine(options);
 this.markAsUntouched(options);
 this.setValue(this._value, options);
}

<button (click)="form.reset({ nickname: 'xx' })">Reset</button>

// Updating value