根据数据结果重复请求

Question

嗨，我是angular的新手，我想知道基于结果数据重复GET请求的正确方法是什么。

item.service.ts

ScanItems():Observable<any>{
    return this.http.get<any>(url)     
}

item.component.ts

GetScannedItems(){
   this.ScanSubscription = this.itemService.ScanItems()
    .subscribe(
       data => {
         RDate = new Date(data.Date).getTime();
         const NDate = new Date().getTime();
         const Diff = RDate - NDate
         if(Diff > (-300000)){
           console.log('Valid')
         }
         else {
           // Repeat Request Here!!!
         }
       },
       error => console.error(error),
       () => this.ScanSubscription.unsubscribe()
   )
}

Answer 1

您可以使用retry运算符在服务中进行操作，而不是在组件中进行处理。

GetScannedItems(){
   this.ScanSubscription = this.itemService.ScanItems()
    .pipe(
      map(
       data => {
         RDate = new Date(data.Date).getTime();
         const NDate = new Date().getTime();
         const Diff = RDate - NDate
         if(Diff > (-300000)){
           return of(true);
         }
         else {
            return Observable.throw('retry');
           // Repeat Request Here!!!
         }
       }),
       delay(500),
       retry()
   )
}