mat-select required validation not working

Question

I have the following code

<form #createForm="ngForm">
 <mat-form-field>
   <mat-select placeholder="Favorite food"
      matInput
     [ngModel]
     food="food"
     #food="ngModel" required>
    <mat-option *ngFor="let food of foods" [value]="food.value">
      {{ food.viewValue }}
    </mat-option>
   </mat-select>
</mat-form-field>
</form>
<button [disabled]="!createForm.valid">submit</button>

Since I want the "selection" is a required field, the "submit" button should be disabled when the form is rendered. However, the "submit" button is enabled when the form is displayed. What is the problem?

Answer 1

This works for me when I (a) use a name attribute and (b) use the two-way ngModel binding syntax.

i.e. Instead of this

<mat-select placeholder="Favorite food" matInput [ngModel] food="food" #food="ngModel" required>

use this:

<mat-select name="food" placeholder="Favorite food" [(ngModel)]="food" required>