How to correctly add "checked" to a radio button group in a loop?

Question

Usually checked just add at the end of input

<input type="radio" name="item" value="value1" checked>
<input type="radio" name="item" value="value2">

But now I am using *ngFor. I want to select the first one.

I try to do this, but it does not work, because checked is not a class.

<div *ngFor="#item of collection; #i = index"">
    <input type="radio" name="item" value="{{item}}" [ngClass]="{'checked':i === 0}">
    <label>{{item}}</label>
</div>

So how can I do it? Thanks!

Answer 1

<input type="radio" name="item" value="{{item}}" [attr.checked]="i === 0 ? '' : null">