實施觀察的失敗，因爲離子2忘記觀察

Question

想實現可觀察到下面的類

import {Injectable, } from '@angular/core'; 
import {Observable} from 'rxjs/Observable'; 
import 'rxjs/add/operator/share'; 
import {Observer} from 'rxjs/Observer'; 

@Injectable() 
export class CalendarService { 

dataChange: Observable<any>; 
dataChangeObserver: Observer<any>; 

    constructor() { 
     this.dataChange = new Observable((observer) => { 
      this.dataChangeObserver = observer; 
     }).share(); 
    } 

    setDate(date: any) { 
     this.dataChangeObserver.next(date); 
    } 
} 

當調用setDate()與價值正在以下錯誤

ORIGINAL EXCEPTION: TypeError: Cannot read property 'next' of undefined 
ORIGINAL STACKTRACE: 
TypeError: Cannot read property 'next' of undefined 

看來，觀察dataChangeObserver未定義。但是在調試時我可以看到我設置的值爲dataChangeObserver。但是，當撥打setDate(date: any)時，Ionic 2會以某種方式忘記它。

Answer 1

請檢查我的問題can i emmit the event from parent to child的答案，看看如何設置Observable以及如何訂閱它。