Encounter the issue of receiving 'undefined' as a response for data that was assigned within

Instead of calling the service in the .ts file and wasting time, I want to assign this as a global value that I can use. However, I keep getting undefined.

Here is my service file

@Injectable({
  providedIn: 'root'
})
export class DeService {

  data:any;

  constructor(private http: HttpClient){}


  getData(id:any):Observable<any>{
    this.http.get(Url.getDetails+"id="+id).pipe(first()).subscribe(res=>{
        this.data = res;
        console.log(this.data)   //Data successfully retrieved here
    }
    return this.http.get(Url.getDetails+"id="+id)
    }
}

The ts file

export class text implements OnInit{

    constructor(public de:DeService){}

    ngOnInIt(){
        console.log(this.de.data);   //Returns undefined here
    }
}

Answer №1

You can't simply access the observable in that way. Instead, you must call the appropriate method and subscribe to it as shown below:

fetchData(id: any): Observable<any> {
  return this.http.get(Url.getDetails + "id=" + id);
}

Then, in your component:

ngOnInit() {
   this.fetchData(id).subscribe((data) => {
     console.log(data);
   });
}

Answer №2

When working with Observable, which deals with asynchronous data, it's important to note that your data:any; variable may not be initialized initially, leading to undefined logs.

A scenario like this might occur:

export class sampleText implements OnInit{

    constructor(public de:DeService){}

    ngOnInIt(){
        console.log(this.de.data);   //this will return undefined
    }
}

Prior to the above code snippet:

  getData(id:any):Observable<any>{
    this.http.get(Url.getDetails+"id="+id).pipe(first()).subscribe(res=>{
        this.data = res;
        console.log(this.data)   //At this point, data is retrieved successfully
    }
    return this.http.get(Url.getDetails+"id="+id)
  }

To resolve this issue, make sure to assign a value to data:any or consider implementing @Sajeetharan's solution.

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