Converting input/select string values into strongly-typed values with Angular 2

I've been searching for a solution for quite some time now, but I'm still a bit confused. The issue is simple: I have a model with a boolean property that I'm mapping to a select element in Angular. The select allows the user to choose between true, false, or null values, but Angular is returning a string. Here's a more concrete example:

In my component:

@Component({
  selector: 'clientlist',
  templateUrl: './app/components/clientlist/clientlist.html'
})

export class ClientListComponent {  
   searchRequest : ClientSearchRequest;
}

Here's the template:

<select [(ngModel)]="searchRequest.online" class="form-control" (onchange)="search()" numberBinder>
    <option value="">Select</option>
    <option value="true">Online</option>
    <option value="false">Offline</option>
</select>

And the ClientSearchRequest model class:

export class ClientSearchRequest {
name: string;
online: boolean;
status: string;
page: number;
pageSize: number;

constructor() {
    this.name = "";
    this.online = null;
    this.status = "";
    this.page = 1;
    this.pageSize = 50;
}

}

When the model gets filled, the online field is set as a string ("true"). How can I resolve this issue without creating additional components?

Answer №1

To enhance your selection process, consider leveraging the ngValue directive. By employing this method, you can utilize an object as opposed to a string for values:

<select [(ngModel)]="searchRequest.online" class="form-control" 
        (onchange)="search()" numberBinder>
  <option [ngValue]="'null'">Select</option>
  <option [ngValue]="true">Online</option>
  <option [ngValue]="false">Offline</option>
</select>

It's worth noting that using a null value may not yield the desired outcome, necessitating the implementation of a workaround. For further insights, refer to this related query:

  • Angular2 select with ngValue null

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