问题描述
我有一个角度应用程序,在某些情况下(软件中的某些触发器或在用户请求时)应与服务器同步某些数据。所以我有这样的功能:
...
public createSyncObservable(): Observable<any> {
return this.retriveDataFromStorage().pipe(
switchMap(
(data) => forkJoin(this.api.sendData1(data.data1),this.api.sendData2(data.data2),this.api.sendData3(data.data3))
),switchMap(
(data) => this.api.getDataFromServer()
),switchMap(
(data) => this.updateLocal(data)
)
)
}
我想要的行为是:
...
public syncData(): Observable<any> {
if (this.observable_complete) {
this.observable_complete = false;
this.syncObservable$ = this.createSyncObservable().pipe(share())
this.syncObservable$.subscribe(
(data) => {this.observable_complete = true}
)
}
return this.syncObservable$;
}
这是要走的路吗?也许我缺少一些RxJS运算符,在这种情况下对我有帮助?这个解决方案似乎有点hacky ...
解决方法
如果调用this.createSyncObservable()
并没有做任何实际的工作,而仅订阅它返回的可观察对象,则只需调用一次该函数。然后,您可以简单地执行以下操作:
public syncData$ = this.createSyncObservable().pipe(share());
如果没有订阅者(例如,share
完成时), this.createSyncObservable()
将从其来源退订。因此,this.syncData$
的订阅者将完成对this.createSyncObservable()
返回的可观察对象的订阅。
// The first subscribe will trigger a subscribe to createSyncObservable()
syncData$.subscribe()
// A second subscribe while the first hasn't completed won't trigger a subscribe
// to createSyncObservable() but instead just wait for its response
syncData$.subscribe()
// After some time ...
// Another subscribe after createSyncObservable() completed will trigger another
// subscribe to createSyncObservable()
syncData$.subscribe()
https://stackblitz.com/edit/rxjs-44qzaj?file=index.ts
,您应该尝试使用takeWhile / skipWhile运算符:
这只是一个例子,但我希望您觉得它有用。
private isResourceFree = true;
public createSyncObservable(): Observable<any> {
return of(isResourceFree).pipe(
takeWhile(val => val),tap(_ => this.isResourceFree = false),switchMap(_ => this.retriveDataFromStorage()),switchMap(
(data) => forkJoin(this.api.sendData1(data.data1),this.api.sendData2(data.data2),this.api.sendData3(data.data3))
),switchMap(
(data) => this.api.getDataFromServer()
),switchMap(
(data) => this.updateLocal(data)
),tap(_ => this.isResourceFree = true)
)
}