title: I'm not getting a correct value of my object list
body: <p>I'm trying to use the TYPEHEAD for my input with the library <a href="https://ng-bootstrap.github.io/#/components/typeahead/examples" rel="nofollow noreferrer">ng-bootstrap</a>, to show the list of objects (just like a select without a box):</p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;input type="search"
         #instance="ngbTypeahead"
         placeholder="Search"
         aria-label="Search"
         [(ngModel)]="model"
         [ngbTypeahead]="search"
         [resultTemplate]="rt"
         [inputFormatter]="formatter"
         (focus)="focus$.next($event.target.value)"
         (click)="click$.next($event.target.value)"
  &gt;
  </code></pre>
  
  <p>When I'm writing a name of my object I'm only getting <code>empty value</code> seven times (all objects that I'm waiting for) if I choose an object the value on the input appears correctly (but in the box it's empty).</p>
  
  <p><strong>TS</strong></p>
  
  <pre><code>  search = (text$: Observable&lt;string&gt;) =&gt;
      text$.pipe(
        debounceTime(200),
        distinctUntilChanged(),
        merge(this.focus$),
        merge(this.click$.pipe(filter(() =&gt; !this.instance.isPopupOpen()))),
        map(term =&gt; (term === '' ? this.productList
          : this.productList.filter(v =&gt; v.name_product.toLowerCase().indexOf(term.toLowerCase()) &gt; -1)).slice(0, 10))
      );
  
     formatter = (x: {name_product: string}) =&gt; x.name_product;
  
      searchUrl(url){
        if(url){
          window.open(url,'_blank');
        }
      }
  </code></pre>
  
  <p><strong>JSON</strong></p>
  
  <pre><code>  productList =
    [ 
      {
          id_product:1,
          name_product: 'Laptop Dell'
      },
      {
          id_product:2,
          name_product: 'Laptop HP'
      },
      {
          id_product:3,
          name_product: 'G-Shock Casio'
      },
      {
          id_product:4,
          name_product: 'Casio LR-T CALC'
      },
      {
          id_product:5,
          name_product: 'LG G3 Stylus'
      },
      {
          id_product:6,
          name_product: 'DYMO 450 Turbo'
      },
      {
          id_product:7,
          name_product: 'Brother QL 700'
      }
    ];
  </code></pre>
  
  <p>But, I need to show the name of my product <code>(name_product)</code>, but in my <code>[(ngModel)]="model"</code> I hope to get the id <code>(id_product)</code>. How can Fix this bug?.</p>
  
  <p>Here it's my <a href="https://stackblitz.com/edit/typehead-ng-bootstrap?file=src/app/app.component.ts" rel="nofollow noreferrer">stackblitz</a> of this bug.</p>