Angular2：需要實例類，以防止無極/物業未找到錯誤

Question

在我的「出口類：」如果我不這樣做：

purchase = new Purchase(); 

我的構造函數之前，然後我得到一個錯誤的承諾，即找不到「名稱」。

我的HTML模板確實結合類：

<h2 text-center><input [(ngModel)]="purchase.name"></h2> 

但我希望由服務噴油器在構造函數中提供了這個類。現在我必須告訴我的詳細控制器關於「購買」類的結構，我可能在單元測試時遇到問題。

任何想法如何避免「purchase = new Purchase（）」？

下面是完整的代碼：

import {Component, OnInit} from "@angular/core"; 
import {PurchaseService} from '../../services/purchase.service'; 
import {Purchase} from '../../services/purchase'; 

@Component({ 
    templateUrl: 'build/pages/detail/detail.html', 
    providers: [PurchaseService] // teach injector how to make a PurchaseService 
}) 

export class DetailPage implements OnInit{ 

    name: String; 
    purchase = new Purchase(); 

    constructor(
    private _navController: NavController, 
    private _navParams: NavParams, 
    private purchaseService: PurchaseService) { 

     this._navController = _navController; 
     this.name = _navParams.get('name'); 
    } 

    ngOnInit() { 
    this.getOnePurchase(); 
    } 

    getOnePurchase() { 
    this.purchaseService.getOnePurchase(name) 
     .then(result => this.purchase = result 
     ) 
     .then(result => console.log(result) 
     ) 
    } 

    pushPage(name: string) { 
    this._navController.pop(); 
    } 
} 

Answer 1

取出new Purchase()和改變你的模板：

<h2 text-center><input [(ngModel)]="purchase?.name"></h2>