Angular 2服务调用未定义Angularfire 2流？

Question

我有一个操作，我使用angularfire2从我的firebase中获取一些数据，映射它并对数据做一些更新/检查，然后我想再次保存它，但是我有这个奇怪的问题，它告诉我'this.fs.getRiders'是未定义的？但我使用服务来创建流，我不确定这里发生了什么。

继承人一些代码

@Injectable() 
     export class RoundService { 

    public currentRound:FirebaseListObservable<any>; 

constructor(private af: AngularFire, private as:AuthService, private fs:FirebaseService) { } 

pullCurrentRound(serieUid:string){ 

    return this.af.database.object(`series/${serieUid}/currentRound`) 
    .flatMap((res)=>{ 
     return this.af.database.object(`rounds/${res.$value}`) 
     .map((res)=>res) 
     .do(this.roundUpdates) 
     .do(this.saveRound) 
    }) 
} 

saveRound(round){ 

    this.fs.getRiders.update(round.uid,round) 
     .then(snap=>{ 
     console.log(snap) 
     }) 
} 

和错误

Uncaught TypeError: Cannot read property 'getRiders' of undefined 
at SafeSubscriber.RoundService.saveRound [as _next] (round.service.ts:57) 
at SafeSubscriber.__tryOrSetError (Subscriber.js:232) 
at SafeSubscriber.next (Subscriber.js:174) 
at Subscriber._next (Subscriber.js:125) 
at Subscriber.next (Subscriber.js:89) 
at DoSubscriber._next (do.js:82) 
at DoSubscriber.Subscriber.next (Subscriber.js:89) 
at DoSubscriber._next (do.js:87) 
at DoSubscriber.Subscriber.next (Subscriber.js:89) 
at MapSubscriber._next (map.js:83) 

任何人有想法？

Answer 1

this没有指向在你期望

pullCurrentRound(serieUid:string){ 

    return this.af.database.object(`series/${serieUid}/currentRound`) 
    .flatMap((res)=>{ 
     return this.af.database.object(`rounds/${res.$value}`) 
     .map((res)=>res) 
     .do(this.roundUpdates.bind(this)) // <<< changed 
     .do(this.saveRound.bind(this) // <<< changed 
    }) 
} 

随着这一变化this保持在中roundUpdates和saveRound

的另一种方式当前类的实例指向使用箭头功能，但他们在你的具体情况下不太方便

pullCurrentRound(serieUid:string){ 

    return this.af.database.object(`series/${serieUid}/currentRound`) 
    .flatMap((res)=>{ 
     return this.af.database.object(`rounds/${res.$value}`) 
     .map((res)=>res) 
     .do(x => roundUpdates(x)) // <<< changed 
     .do(round => this.saveRound(round) // <<< changed 
    }) 
}