Passing object in ngModel to a custom control Angular2

Question

I want to create custom control which contains other custom controls and use ngModel that connects all of them. Like :

PersonSearchComponent :

• DeveloperSearchControl
  • Name - some string input
  • Surname
  • ProffesionSelect - custom control expecting ProffesionModel
• BuildingSearchControl
  • Some custom controls here
• CountryCustomControl - custom control expecting CountryModel

---

• PersonListComponent : -imported data about items from PersonSearchComponent by some service

---

• SomeOtherSearchComponent
  • DeveloperSearchControl - reusable

So for now I have working version, but I think i have made something bad (maybe I should use FormBuilder):

PersonSearch Template :

    <div>
            <developer-search-control [(ngModel)]="searchModel.developerSearchModel"></developer-search-control>
            <building-search-control [(ngModel)]="searchModel.buildingSearchModel"></building-search-control>
            <country-select [(ngModel)]="searchModel.countryModel"><country-select>
    </div>

ParentSearch component

...
export class PersonSearch {
  @Output() searchDataEmitter= new EventEmitter();//Exports data to above component which contains this, and listComponent
searchModel : PersonSearchModel : new PersonSearchModel();

    performSearch()
    {
        //gets data from service with searchModel and searchDataEmitter transpors it to above component
    }
}

Models : PersonSearchModel :

developerSearchModel : DeveloperSearchModel = new DeveloperSearchModel();
buildingSearchModel: BuildingSearchModel = new BuildingSearchModel();
countryModel : CountryModel;

DeveloperSearchModel :

name : string
surname : string
proffesion : ProfessionModel

Template developerSearchControl.component.html:

<div *ngIf="value">//This is the problem
     <input [(ngModel)]="value.name"></input>
     <input [(ngModel)]="value.surname"></input>
     <profesion-select [(ngModel)]="value.ProffesionSelect">
</div>

developerSearchControl.component:

...
@Component({
  selector: 'developer-search-control',
  templateUrl: './developerSearchControl.component.html',
  providers: [{
    provide: NG_VALUE_ACCESSOR,
    useExisting: forwardRef(() => DeveloperSearchControlComponent),
    multi: true,
  }],
})

export class DeveloperSearchControlComponent extends ElementBase<DeveloperSearchModel > {
  protected model: NgModel;

  constructor(
    @Optional() @Inject(NG_VALIDATORS) validators: Array<any>,
    @Optional() @Inject(NG_ASYNC_VALIDATORS) asyncValidators: Array<any>,
  ) {
    super(validators, asyncValidators);
  }
}

profesionSelect.component

    ...
@Component({
    selector: 'profesion-select',
    template: `
     <div>
        <label *ngIf="label">{{label}}</label>
        <dx-select-box 
            [dataSource]="data" 
            [(ngModel)]="value" 
            displayExpr="proffesionName" 
            [placeholder]="placeholder"
            [searchEnabled]="true"
            >
        </dx-select-box>
    </div>`,
        providers: [{
        provide: NG_VALUE_ACCESSOR,
        useExisting: ProfessionComponent,
        multi: true,
    }],
})

export class ProfessionComponent extends ElementBase<string> implements OnInit {
    private data: ProfessionModel[];
    private label: string = 'proffesion :';
    private placeholder: string = 'Select profession';
    @ViewChild(NgModel) model: NgModel;

    constructor(private proffesionService: ProfessionDataService,
        @Optional() @Inject(NG_VALIDATORS) validators: Array<any>,
        @Optional() @Inject(NG_ASYNC_VALIDATORS) asyncValidators: Array<any>,
    ) {
        super(validators, asyncValidators);
    }

    ngOnInit() {
        this.professionService.getDevelopersProfessions().subscribe(
            data => {
                this.data = data;
            }
        );
    }
}

ElementBase is a generic ControlValueAccessor with validation from : http://blog.rangle.io/angular-2-ngmodel-and-custom-form-components/

So my problem is that when I create the template for children (developerSearch, buildingSearch) the value passed with ngModel is not initialized for them and i get :

EXCEPTION: Uncaught (in promise): Error: Error in ./DeveloperSearchControlComponent class DeveloperSearchControlComponent - inline template:2:33 caused by: Cannot read property 'name' of null
Error: Error in ./DeveloperSearchControlComponent class DeveloperSearchControlComponent - inline template:2:33 caused by: Cannot read property 'name' of null

Because the value from ngModel is null at start. So I have to use *ngFor="value" in templates of child components which looks bad. Is there any solution to initialize the object before template verification? or Im doing this very wrong?

Answer 1

There's a way to use two-way binding with safe-navigation operator:

<input [ngModel]="value?.name" (ngModelChange)="value?.name ? value.name = $event : null"> 

Props to: https://stackoverflow.com/a/36016472/5706293