Angular Angularfire 2 流未定义 2 服务调用？

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 updates/checks 然后我想再次保存它但是我遇到了这个奇怪的问题它告诉我 'this.fs.getRiders' 未定义？但是我正在使用服务来创建流，我不太确定这里发生了什么。

这里是一些代码

 @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)
      })
}

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)

有人有想法吗？

Answer 1

this 没有指向您期望的位置

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
    })
}

通过此更改，this 继续指向 roundUpdates 和 saveRound

中的当前 class 实例

另一种方法是使用箭头函数，但它们在您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
    })
}

Angular Angularfire 2 流未定义 2 服务调用？

Angular 2 Service call is undefined from Angularfire 2 stream?

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angular