Angular 2 : using [class.someClass] causes `No provider for ControlContainer!`?

Question

I'm working on a project using angular 2. I'm dealing with forms and validation and I have an issue. I've just found a workaround but I would like to know why my original code doesn't works.

Here is my code (refractored) :

@Component({
    directives: [ DisplayErrorComponent ],
    styleUrls: ["src/modules/component@channel/src/add/add.css"],
    template: `        
        <form (ngSubmit)="onSubmit()" [ngFormModel]="channelForm">
            <label for="link">
                Customize the link
                <!--<div class="link inputBordered inputTexted" [ngClass]="{error: !channelForm.controls.link.valid}">-->
                <div class="link inputBordered inputTexted" [class.error]="!channelForm.controls.link.valid">
                    <span class="static">http://www.monsite.fr/mediatheque/</span>
                    <input type="text" name="link" ngControl="link" required>
                </div>
            </label>
            <input type="submit" value="Add" [disabled]="!channelForm.valid">
        </form>
    `
})
export class EditComponent {
    channel: Media;
    channelForm: ControlGroup;
    categories: Category[] = this._categoryService.listAll();

    constructor(fb: FormBuilder, private _categoryService: CategoryService, private _routeParams: RouteParams, private _mediaService: MediaService) {
        this.channel = this._mediaService.getById(this._routeParams.get('id'));
        this.channelForm = fb.group({
            link        : fb.control(this.channel.link, Validators.compose([Validators.required, UrlValidator])),
        });
    }

    onSubmit():void {
        console.log('form submitted')
    }
}

The anomaly is at line 8-9. You can see a commented line. When I use [class.error]="true" , Angular throws an error :

EXCEPTION: Error: Uncaught (in promise): No provider for ControlContainer! (NgControlName -> ControlContainer)

But when I try with [ngClass] , everything works. Why ? (I can post all the edit.component.ts code if needed).

Answer 1

如类似问题https://github.com/angular/angular/issues/8165中所述，这是一个已知问题（ https://github.com/angular/angular/issues/6374 ）

Answer 2

You need to use this instead:

<input type="text" name="link" 
  [ngFormControl]="channelForm.controls.link" required>

Because ngControl is for inline form declaration and you use FormBuilder to define your link control.