javascript - Angular 4 setting selected option in Dropdown

Question

There are several questions about this and different answers but none of them really answers the question. So again:

Setting default of a Dropdown select by value isn't working in my case. Why? This is from the dynamic Form tutorial of Angular 4:

<select [id]="question.key" [formControlName]="question.key">
      <option *ngFor="let opt of question.options" [value]="opt.key" [selected]="opt.selected">{{opt.selected+opt.value}}</option>
</select>

It doesn't select anything. Available options are:

• trueaaa
• falsebbb
• falseccc

But static true:

<option ... [selected]="true">...</option>

selects the last value (all true). It also works with a private variable boolvar = true and using it in [selected]="boolvar"

I don't understand the difference between the "opt" object and the class variable.

Answer 1

If you want to select a value based on true / false use

[selected]="opt.selected == true"

 <option *ngFor="let opt of question.options" [value]="opt.key" [selected]="opt.selected == true">{{opt.selected+opt.value}}</option>

checkit out

Angular 2 - Setting selected value on dropdown list