multiple mat-select start with all checked?

Question

I have a dinamicly mat-select in an Angular4 app. What I need is: when I fill the mat-select options, I need to set all the options as checked. I tried many thins but no one worked. Please help.

This is what I got:

ts:

options = {
    0: 'op1',
    1: 'op2',
    2: 'op3',
    3: 'op4'
  };

but the options variable can change. Sometimes the length can be 5, sometimes can be 16, sometimes 0, that is dinamic.

Then, in my HTML i got this:

<mat-select multiple placeholder="Options" required="true" [(ngModel)]="selected-options">
  <mat-option *ngFor="let op of options" [value]="op">{{ op }}</mat-option>
</mat-select>

Look the multiple in the mat-select tag.

THIS WORKS! but that just set the options in the select and the value is unchecked.

So... how can I set all the items checked?

Answer 1

Try this:

HTML:

<mat-select multiple placeholder="Options" required="true" [formControl]="selectedOptions">
  <mat-option *ngFor="let op of options" [value]="op">{{ op }}</mat-option>
</mat-select>

In your TS:

options: string[] = {'op1','op2','op3','op4'};
selectedOptions = new FormControl(this.options);