The Observable type with MyData as the parameter cannot be assigned to MyData directly

export class MyClass {
    data: MyData;  
    constructor(private dataService: DataService) {    
      this.data = this.dataService.getData(); // issue             
    }
}


export class DataService{
    data: MyData; 
     constructor(private http: Http) { }

    getData(): Observable<MyData>{
       return Observable.from([this.fakeData()]
          .map(res=>res as MyData));
    }   

    private fakeData() : MyData {   
       ...  
    }
}

An error has occurred on line

 this.data = this.dataService.getData()

The type Observable cannot be assigned to MyData

Answer №1

Typescript is the way to go.

Within your component, you specified that the variable data should be of type MyData. However, in your constructor, you are calling a service that returns an Observable containing a MyData object and attempting to assign this value directly to your data attribute.

This approach does not align with how Observables function.

There are two straightforward solutions available:

Subscribing to the Observable

export class MyClass {
    data: MyData;  
    constructor(private dataService: DataService) {    
      this.dataService.getData().subscribe((myData) => {
        this.data = myData;
      });  
    }
}

Alternatively, utilize the AsyncPipe within your template

export class MyClass {
    data$: Observable<MyData>; // Adjust the type as needed.
    // The $ suffix convention signifies that
    // this attribute is an observable.

    constructor(private dataService: DataService) {    
      this.data$ = this.dataService.getData();  
    }
}

Then, within your template, make use of data along with the AsyncPipe

<div>
    <some-component [someData]="data$ | async"></some-component>
</div>

Answer №2

Give this a shot - define 'data' as an observable of MyData

class YourClass {
  data: Observable<MyData>;   
 constructor(private service: DataService) {    
   this.data = this.service.retrieveData(); // encountered issue             
 }
}

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