Take a look at this snippet from my AngularJS 2 application:
DataItem
export class DataItem {
id: number;
name: string;
}
DataService
[...]
export class DataService {
constructor(private http: Http) {}
fetchData(): Observable<DataItem> {
return this.http
.get("http://www.example.com")
.map(this.save)
.catch(this.fail);
}
private save(response: Response) {
let dataItem: DataItem = <DataItem> response.json();
return dataItem || {};
}
private fail(error: any) {
return Observable.throw("error!");
}
}
MainComponent
[...]
export class MainComponent implements OnInit {
dataItem: DataItem;
constructor(private dataService: DataService) {}
ngOnInit() {
this.dataService.fetchData().subscribe(
result => {
this.dataItem = new DataItem();
console.log(this.dataItem); // prints (empty) DataItem
this.dataItem = result;
console.log(this.dataItem); // prints object, not DataItem?
},
error => { }
);
}
}
Now, I have some questions:
1) Why is the type object printed in Chrome Inspector instead of DataItem?
2) The property dataItem in the MainComponent class should be of type DataItem. Why isn't there an error?
3) How can I ensure that I actually receive DataItem? What is the best way to achieve this? Is there a way to automatically map the JSON response to my object?