I get undefined from calling a service in a component Angular 8

Question

I have created an interface and a service in which this service is responsible for getting some data from API, but when I try to call that from a component, it returns undefined to me. these are my services and my component (I have also noticed that the function within the service returns void, and I have provided them in the app.module )

@Injectable()

export class TasksService {
    compeletedTasks: Task[];
    constructor(public http: Http) {}

    getCompeletedTasks(): Observable<Task[]>{
        return this.http.get("http://localhost:4000/api/compeleted");
    }

and this is my component:

import { TasksService } from '../../services/tasks.service';

export class DoneTaskItemsComponent implements OnInit {
    constructor(private tasksService:TasksService){}

    ngOnInit() {
        this.tasksService.getCompeletedTasks().
        subscribe(response => console.log(response))
    }

So any solution for that? I need to use the compeletedTasks on the template, but for now, when I log them on the console, I get undefined.