Setting the default value for Angular Material's select component (mat-select)

Many inquiries are focused on setting a default value to display in a "Select" control. In this particular case regarding Angular 8 template driven forms, the issue lies in the inability to show the default value in the mat-select when the button is clicked, despite the console.log reflecting the correct value:

<mat-select [formControl]="itemControl" required [(value)]="itemValue">
    <mat-option>--</mat-option>
    <mat-option *ngFor="let item of items" [value]="item">{{item}}</mat-option>
</mat-select>

The relevant part of my component code appears as follows:

export class MyComponent {

  items: string[] = [''];
  itemControl = new FormControl('', [Validators.required]);
  itemValue: string = '';

  myButtonClick(): void {
        this.itemValue = this.getItems()[0];     <--- This returns the first element in a valid array
        console.log(this.itemValue);
      }
}

What could be causing this issue?

Answer №1

When utilizing form control, it's important to set the default value for itemControl. This can be achieved by using the following code:

this.itemControl.patchValue(this.getItems()[0])

The assignment can be done either in the onInit lifecycle hook or from the API response. By doing so, the form control will be able to update the value accordingly. It's worth noting that the mat-select directive does not support two-way data binding for the value property.

Answer №2

Illustration:

Markup:

 <div [ngClass]="{ 'active': isActive }">
       <p>Click me!</p>
   </div>

.component.ts:

public isActive: boolean = false;

toggleActive() {
    this.isActive = !this.isActive;
}

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