Accessing observable property in Angular 2 with TypeScript: A comprehensive guide

My observable is populated in the following manner:

this._mySubscription = this._myService.fetchData(id)
                                .subscribe(
                                    response => this._myData = response, 
                                    error => this.displayError(<any>error),
                                    () => this.stopLoading()
                                );

In my HTML markup, I can access its properties using the Elvis operator like so:

{{_myData?.PropertyNameHere}}

However, how can I access the same property in the component using TypeScript?

Attempting to do so results in a red squiggly line under the property:

this._myData.PropertyNameHere

And displays the error message:

Property does not exist on Observable

Update: Example of service call

fetchData(id: string): Observable<any> {

let params = 'id=' + id;

return this._http
            .post(apiUrl + 'SomeController/SomeAction', params, {withCredentials: true, headers: this.headers})
            .timeoutWith(maxTimeHttpCalls, Observable.defer(() => Observable.throw(this._feedbackService.timeout())))
            .map((response: Response) => response.json().data.Items);

}

Answer №1

_myData within the class should not be of type Observable. Instead, it should match the type of the object returned from the map operator in your service.

.map((response: Response) => response.json().data.Items)

The type of data.Items should determine the type of _myData. If the exact type is unknown, you can set it to any to avoid compiler warnings. However, defining a model class for stronger typing is recommended if you are familiar with the data structure.

interface SomeModel {
  somProperty: string;
}

getSomething(id: string): Observable<SomeModel> {

  return this._http
             ...
             .map((response: Response) => <SomeModel>)response.json().data.Items);
}

Your component

class MyComponent {
  private _myData: SomeModel;

  this._mySubscription = this._myService.getSomething(id)
    .subscribe((response: SomeModel) => this._myData = response, 
               error => this.displayError(<any>error),
               () => this.stopLoading());
}

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