ngModel cannot be used to register form controls with a parent formGroup directive

问题

After upgrading to RC5 we began getting this error:

ngModel cannot be used to register form controls with a parent formGroup directive.  Try using
  formGroup's partner directive "formControlName" instead.  Example:


<div [formGroup]="myGroup">
  <input formControlName="firstName">
</div>

In your class:

this.myGroup = new FormGroup({
   firstName: new FormControl()
});

  Or, if you'd like to avoid registering this form control, indicate that it's standalone in ngModelOptions:

  Example:


<div [formGroup]="myGroup">
   <input formControlName="firstName">
   <input [(ngModel)]="showMoreControls" [ngModelOptions]="{standalone: true}">
</div>

It looks like in RC5 the two can no longer be used together, but I could not find an alternative solution.

Here is the component producing the exception:

<select class="field form-control" [formGroup]="form" [(ngModel)]="cause.id" [name]="name">
<option *ngFor="let c of causes" [value]="c.text">{{c.text}}</option>
</select>

回答1:

The answer is right on the error message, you need to indicate that it's standalone and therefore it doesn't conflict with the form controls:

[ngModelOptions]="{standalone: true}"

回答2:

Expanding on @Avenir Çokaj's answer

Being a novice even I did not understand the error message clearly at first.

What the error message indicates is that in your formGroup you have an element that doesn't get accounted for in your formControl. (Intentionally/Accidentally)

If you intend on not validating this field but still want to use the ngModel on this input element please add the flag to indicate it's a standalone component without a need for validation as mentioned by @Avenir above.

回答3:

OK, finally got it working: see https://github.com/angular/angular/pull/10314#issuecomment-242218563

In brief, you can no longer use name attribute within a formGroup, and must use formControlName instead

回答4:

when you write formcontrolname Angular 2 do not accept. You have to write formControlName . it is about uppercase second words.

<input type="number" [(ngModel)]="myObject.name" formcontrolname="nameFormControl"/>

if the error still conitnue try to set form control for all of object(myObject) field.

between start <form> </form> for example: <form [formGroup]="myForm" (ngSubmit)="submitForm(myForm.value)"> set form control for all input field </form>.

回答5:

import { FormControl, FormGroup, AbstractControl, FormBuilder, Validators } from '@angular/forms';


    this.userInfoForm = new FormGroup({
      userInfoUserName: new FormControl({ value: '' }, Validators.compose([Validators.required])),
      userInfoName: new FormControl({ value: '' }, Validators.compose([Validators.required])),
      userInfoSurName: new FormControl({ value: '' }, Validators.compose([Validators.required]))
    });

<form [formGroup]="userInfoForm" class="form-horizontal">
            <div class="form-group">
                <label class="control-label"><i>*</i> User Name</label>
                    <input type="text" formControlName="userInfoUserName" class="form-control" [(ngModel)]="userInfo.userName">
            </div>
            <div class="form-group">
                <label class="control-label"><i>*</i> Name</label>
                    <input type="text" formControlName="userInfoName" class="form-control" [(ngModel)]="userInfo.name">
            </div>
            <div class="form-group">
                <label class="control-label"><i>*</i> Surname</label>
                    <input type="text" formControlName="userInfoSurName" class="form-control" [(ngModel)]="userInfo.surName">
            </div>
</form>

回答6:

If component has more than 1 form, register all controls and forms

I needed to know why this was happening in a certain component and not in any other component.

The issue was that I had 2 forms in one component and the second form didn't yet have [formGroup] and wasn't registered yet since I was still building the forms.

I went ahead and completed writting both forms complete without leaving a input not registered which solve the issue.

回答7:

I just got this error because I did not enclose all my form controls within a div with a formGroup attribute.

For example, this will throw an error

<div [formGroup]='formGroup'>
</div>
<input formControlName='userName' />

This can be quite easy to miss if its a particularly long form.

回答8:

If you want to use [formGroup] with formControlName, you must replace name attribute with formControlNameformControlName.

Example:

This does not work because it uses the [formGroup] and name attribute.

<div [formGroup]="myGroup">
   <input name="firstName" [(ngModel)]="firstName">
</div>

You should replace the name attribute by formControlName and it will work fine like this following:

<div [formGroup]="myGroup">
   <input formControlName="firstName" [(ngModel)]="firstName">
</div>

来源：https://stackoverflow.com/questions/39126638/ngmodel-cannot-be-used-to-register-form-controls-with-a-parent-formgroup-directi