问题描述
我正在尝试用响应式形式来做一些事情,但很难实现我认为很简单的事情。
我想遍历元素并将它们显示为表单控件。
我目前拥有:
@Component({
selector: 'app-reactive-form-test',styleUrls: ['./reactive-form-test.component.scss'],template: `
<form [formGroup]="questionForm">
<ng-container formArrayName="questions" *ngFor="let question of questionForm.controls; let i = index">
<input type="text" formControlName="i">
</ng-container>
</form>
`
})
export class ReactiveFormTestComponent implements OnInit {
questionForm: FormGroup;
questions: ScheduledQuestionInterface[];
constructor(private fb: FormBuilder) { }
ngOnInit(): void {
this.questionForm = this.fb.group({
questions: this.fb.array([])
});
this.questions = [];
this.questions.push(new ScheduledQuestion(1,1,1));
this.questions.push(new ScheduledQuestion(2,3,2));
this.questions.push(new ScheduledQuestion(3,4,3));
this.questions.forEach(value => {
const control = this.questionForm.get('questions') as FormArray;
control.push(this.fb.group({
id: [value.id],deliveryDateTime: [value.deliveryDateTime]
}));
});
}
}
现在我收到以下错误:
Cannot find a differ supporting object '[object Object]' of type 'object'. NgFor only supports binding to Iterables such as Arrays.
。
我需要对这段代码做什么才能简单地显示来自 3 个 ScheduledQuestion
对象的 3 个文本字段?
解决方法
questionForm.controls
是一个对象,其键为 formControls
基本上在您的情况下
{
questions: []
}
您正在尝试遍历上述不可迭代的对象,因此出现错误
下面应该可以
@Component({
selector: 'app-reactive-form-test',styleUrls: ['./reactive-form-test.component.scss'],template: `
<form [formGroup]="questionForm">
<ng-container formArrayName="questions">
<ng-container *ngFor="let question of questionControls.controls; let i = index">
<input type="text" [formGroupName]="i">
</ng-container>
</ng-container>
</form>
`
})
export class ReactiveFormTestComponent implements OnInit {
questionForm: FormGroup;
questions: ScheduledQuestionInterface[];
get questionControls() {
return this.questionForm.get('questions') as FormArray;
}
constructor(private fb: FormBuilder) { }
ngOnInit(): void {
this.questionForm = this.fb.group({
questions: this.fb.array([])
});
this.questions = [];
this.questions.push(new ScheduledQuestion(1,1,1));
this.questions.push(new ScheduledQuestion(2,3,2));
this.questions.push(new ScheduledQuestion(3,4,3));
this.questions.forEach(value => {
const control = this.questionForm.get('questions') as FormArray;
control.push(this.fb.group({
id: [value.id],deliveryDateTime: [value.deliveryDateTime]
}));
});
}
}
,
这里的问题是你试图循环questionForm.controls
,它是不可迭代的,它是一个对象,它不是你需要的,你也不需要重复表单数组,你需要循环遍历此数组中的控件
来自Angular References的示例:
<div formArrayName="cities">
<div *ngFor="let city of cities.controls; index as i">
<input [formControlName]="i" placeholder="City">
</div>
</div>
因此,您的输入/控件需要有 NgFor,并且循环应该结束 questions.controls