Observable - Observer

TodosService.ts

import { Http } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import { Observer } from 'rxjs/Observer';
import 'rxjs/add/operator/share';
import { Todo } from 'app/interfaces';

export class TodosService {
    todos$: Observable<Todo[]>;
    private _todosObserver: Observer<Todo[]>;
    private _dataStore: {
        todos: Todo[]
    };

    constructor(private _http: Http) {
        this._dataStore = { todos: [] };

        // Create Observable Stream to output our data
        this.todos$ = new Observable(observer => this._todosObserver = observer).share();
    }
}