Angular 6 - How to read values of dynamic ng-model?

Question

This response is working to display many inputs. But values are not readed.

in my html, I added:

<div class="item_key" *ngFor="let x of demo">
    <span class="key_span">Value</span>
    <input [(ngModel)]="teller[x.id]"  class="add_key">
</div>
<pre>{{teller | json}}</pre>

in my ts file, I added:

teller = {};
    demo = [{
        'id': 1
    }, {
        'id': 2
    }];

But the teller still as {}