Angular 2 Input validation with value binding

Question

I have in my project a form with an input like this:

@Input()
article: Article;
ngOnInit() {
this.articleForm = this.formBuilder.group({
  title: [ '', Validators.required]
});

form.component.html:

<input class="form-control" formControlName="title"
           type="text" value="{{article ? article.title : ''}}" />

Article is an Object with title attribute and article is an input property.

The Problem is when the input property get an article with a valid title the input value change to the value of the title but strangely steal in invalid state !

Can any one give me an idea of what happening please ?

Thanks in advance.

First thing, 'value="{{article ? article.title : ''}}"' can be simplified to 'value="{{article?.title}}"' — wannadream
– wannadream, Commented May 24, 2017 at 17:13

AVJT82 · Accepted Answer · 2017-05-24 17:28:04Z

1

This is because the reactive form doesn't register the value of value. If you use one-way-binding your form control will register it:

<input formControlName="title" [ngModel]="article?.title" />

Notice the safe navigation operator here, so that it will not throw error if there is no value.

answered May 24, 2017 at 17:28

AVJT82

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