在角度2訂閱後未定義的值，但在templateurl它可以顯示

Question

我試圖從我的服務處理值它返回未定義的值。但奇怪的是，如果我直接訪問它的模板，這是工作。

這是我的服務

import { Injectable }  from '@angular/core'; 
import { Http, Response } from '@angular/http'; 
import { Observable }  from 'rxjs/Observable'; 
import {Globals} from "../globals"; 
import 'rxjs/Rx'; 
import 'rxjs/add/operator/map'; 
import {DetailprodComponent} from './detailprod.component'; 
import {Home} from '../home/home'; 
import { ActivatedRoute,Router } from '@angular/router'; 

@Injectable() 
export class DetailprodService { 
    private id:string; 
    constructor (private http: Http, private route: ActivatedRoute) { 
     this.route.params.subscribe(params => {let id = params['id'];this.id = id;}); 
    } 

    getDetail(){ 
     return this.http.get(Globals.server+'/product/'+this.id) 
        .map(res=> res.json()); 
    } 

} 

和部件，在OnInit方法我把

this.detailprodService.getDetail() 
     .subscribe(details => this.product_rating = details.product_rating, 
      error => this.errorMessage = <any>error); 
this.getstars(this.product_rating); 

然後如果在HTML我把{{product_rating}}它顯示的輸出。但如果我在組件中進一步處理它，它會導致未定義的值。我送product_rating到方法this.getstars（this.product_rating）

getstars(x){ 
    alert(x) 
    if (x == 2){ 
     alert("1"); 
     this.starspath ="imagemanagement/1stars.png"; 
    }else if (x == 4){ 
     alert("2"); 
     this.starspath ="imagemanagement/2stars.png"; 
    }else if (x == 6){ 
     alert("3"); 
     this.starspath ="imagemanagement/3stars.png"; 
    }else if (x == 7){ 
     alert("4"); 
     this.starspath ="imagemanagement/4stars.png"; 
    }else if (x == 10){ 
     alert("5"); 
     this.starspath ="imagemanagement/5stars.png"; 
    } 
    } 

任何答案將高度讚賞...

Answer 1

嘗試象下面這樣：

this.detailprodService.getDetail() 
      .subscribe(details => { 
this.product_rating = details.product_rating; 
this.getstars(this.product_rating); 
}, error => this.errorMessage = <any>error); 

應等待訂閱新來處理價值。