Typescript AngularFire2-Ionic-无法读取未定义的属性

HTML抛出了一个未定义的错误，就好像没有检索到数据一样。这是我对Firebase列表的服务呼叫：

服务台

 getGames(eventId) {
    var ref =  this.afd.list('/game/', ref => ref.orderByChild('event').equalTo(eventId)).valueChanges();

    return ref;

}

我的网页

currentEvent: any;
 gamesList: any[];
constructor(public navCtrl: NavController, public navParams: NavParams, public 
firebase: FirebaseProvider) {
 this.currentEvent = navParams.get('data');
 this.firebase.getGames(this.currentEvent).subscribe((val: any) => {
   val.forEach((e) => {

    console.log("date " + e.date);
  })

  this.gamesList = val;
})

}

在foreach语句中，我在日志中正确地看到了数据。它会在html上抛出一个错误，即使看起来“gamesList”已填充

page.html

 <ion-list>
  <ion-list-header>Games</ion-list-header>
   <ion-item ngFor="let g of gamesList">
     {{g.date}}
   </ion-item>
 </ion-list>

游戏
{{g.date}

完全错误：

  Unhandled Promise rejection: Cannot read property 'date' of undefined ; Zone: <root> ; Task: Promise.then ; Value: TypeError: Cannot read property 'date' of undefined
    at Object.eval [as updateRenderer] (LandetailPage.html:20)
    at Object.debugUpdateRenderer [as updateRenderer] (core.js:14735)
    at checkAndUpdateView (core.js:13849)
    at callViewAction (core.js:14195)
    at execComponentViewsAction (core.js:14127)
    at checkAndUpdateView (core.js:13850)
    at callWithDebugContext (core.js:15098)
    at Object.debugCheckAndUpdateView [as checkAndUpdateView] (core.js:14635)
    at ViewRef_.detectChanges (core.js:11619)
    at NavControllerBase._viewAttachToDOM (nav-controller-base.js:460) TypeError: Cannot read property 'date' of undefined
    at Object.eval [as updateRenderer] (ng:///AppModule/LandetailPage.ngfactory.js:66:27)
    at Object.debugUpdateRenderer [as updateRenderer] (http://localhost:8100/build/vendor.js:15277:21)
    at checkAndUpdateView (http://localhost:8100/build/vendor.js:14391:14)
    at callViewAction (http://localhost:8100/build/vendor.js:14737:21)
    at execComponentViewsAction (http://localhost:8100/build/vendor.js:14669:13)
    at checkAndUpdateView (http://localhost:8100/build/vendor.js:14392:5)
    at callWithDebugContext (http://localhost:8100/build/vendor.js:15640:42)
    at Object.debugCheckAndUpdateView [as checkAndUpdateView] (http://localhost:8100/build/vendor.js:15177:12)
    at ViewRef_.detectChanges (http://localhost:8100/build/vendor.js:12161:22)
    at NavControllerBase._viewAttachToDOM (http://localhost:8100/build/vendor.js:54343:40)
n.onUnhandledError @ polyfills.js:3
r @ polyfills.js:3
(anonymous) @ polyfills.js:3
n.microtaskDrainDone @ polyfills.js:3
o @ polyfills.js:3
Promise.then (async)
r @ polyfills.js:3
t.scheduleTask @ polyfills.js:3
r.scheduleTask @ polyfills.js:3
r.scheduleMicroTask @ polyfills.js:3
f @ polyfills.js:3
t.then @ polyfills.js:3
NavControllerBase._nextTrns @ nav-controller-base.js:246
NavControllerBase._queueTrns @ nav-controller-base.js:185
NavControllerBase.push @ nav-controller-base.js:70
webpackJsonp.184.LanPage.goToLAN @ lan.ts:58
(anonymous) @ LanPage.html:22
handleEvent @ core.js:13589
callWithDebugContext @ core.js:15098
debugHandleEvent @ core.js:14685
dispatchEvent @ core.js:10004
(anonymous) @ core.js:10629
(anonymous) @ platform-browser.js:2628
globalListener @ platform-browser.js:3196

未处理的承诺拒绝：无法读取未定义的属性“日期”；区域：；任务：承诺；值：TypeError:无法读取未定义的属性“date”
在Object.eval[作为更新者]（LandetailPage.html:20）
在Object.debugUpdateRenderer[作为updateRenderer]（core.js:14735）
在checkAndUpdateView（core.js:13849）
在callViewAction上（core.js:14195）
在execComponentViewsAction（core.js:14127）
在checkAndUpdateView（core.js:13850）
在callWithDebugContext上（core.js:15098）
在Object.debugCheckAndUpdateView[作为checkAndUpdateView]（core.js:14635）
在ViewRef_u2;.detectChanges（core.js:11619）
在NavControllerBase.\u viewAttachToDOM（nav controller base.js:460）类型错误：无法读取未定义的属性“date”
在Object.eval[as updateRenderer]（ng:///AppModule/LandetailPage.ngfactory.js:66:27）
在Object.debugUpdateRenderer[作为updateRenderer](http://localhost:8100/build/vendor.js:15277:21)
在checkAndUpdateView(http://localhost:8100/build/vendor.js:14391:14)
在callViewAction(http://localhost:8100/build/vendor.js:14737:21)
在执行组件视图操作时(http://localhost:8100/build/vendor.js:14669:13)
在checkAndUpdateView(http://localhost:8100/build/vendor.js:14392:5)
在callWithDebugContext(http://localhost:8100/build/vendor.js:15640:42)
在Object.debugCheckAndUpdateView[作为checkAndUpdateView](http://localhost:8100/build/vendor.js:15177:12)
在ViewRef_u3;检测更改时(http://localhost:8100/build/vendor.js:12161:22)
在导航控制器基座上(http://localhost:8100/build/vendor.js:54343:40)
n、 onUnhandleError@polyfills.js:3
r@polyfills.js:3
（匿名）@polyfills.js:3
n、 microtaskDrainDone@polyfills.js:3
o@polyfills.js:3
Promise.then（异步）
r@polyfills.js:3
t、 scheduleTask@polyfills.js:3
r、 scheduleTask@polyfills.js:3
r、 scheduleMicroTask@polyfills.js:3
f@polyfills.js:3
t、 然后@polyfills.js:3
NavControllerBase.\u nextTrns@nav controller base.js:246
NavControllerBase.\u queueTrns@nav controller base.js:185
NavControllerBase.push@nav controller base.js:70
webpackJsonp.184.LanPage.goToLAN@lan.ts:58
（匿名）@LanPage.html:22
handleEvent@core.js:13589
callWithDebugContext@core.js:15098
debugHandleEvent@core.js:14685
dispatchEvent@core.js:10004
（匿名）@core.js:10629
（匿名）@platform browser.js:2628
globalListener@platformbrowser.js:3196

---

谢谢你的帮助

我认为问题在于，在从firebase获取数据之前，html试图在gamesList中循环。您需要将其设置为异步

<ion-item ngFor="let g of gamesList | async">

---

您能在问题中添加准确的错误消息吗？不幸的是，这是我尝试的另一条导致相同错误的路径。我将发布完整错误。如果您不使用异步管道，您仍然可以使用与在subscribe（）中设置gamesList相同的方法。但在html中，您需要首先检查gameList是否为null：

*ngIf=“gamesList”

然后在其中执行for循环。

this.gamesList = this.firebase.getGames(this.currentEvent)