Ion select default ion-option

Hello everyone,

I have dynamis ion-select combined with ion-option

example :

<ion-item no-lines   *ngFor="let attr of attributes">
    <ion-select [formControlName]="attr.key">
      <ion-option *ngFor="let option of attr.values" selected="{{(attr.values.length > 1) ? false : true }}" [value]="option">{{option}}</ion-option>

I try to set the ion-option selected as default when my array values size is equals to 1.
That didn’t work. Do you have a way to set default selected value to ion-option ?
Ty in advance