Angular RxJS - 只有当订阅另一个 Observable 给出特定结果时才订阅 Observable

Question

我需要某种特殊的 RxJS 语法（如果它适用于这种情况）：

    this.electronicInvoiceService.getElectronicInvoice(this.invoiceId)
            .subscribe(and here I can get .isApproved, for example: 
        (data) => data.isApproved 
        and what I want is IF data.isApproved is false only then 
        I want to subscribe to this 
        next observable I wrote below this);

仅当 isApprove 为 false 时才执行下一次订阅

  this.electronicInvoiceStagingService.getElectronicInvoice(this.invoiceId).subscribe();

我已经尝试过的：我尝试在我的 ts 文件和内部订阅中添加一些变量我做了 this.myVariableName == data.isApproved 但这没有用我认为因为订阅需要一些时间这是错误的逻辑。

[解决方案]：下面的评论解决了它，我真傻我没有马上使用它（：解决方案>为什么简单的 if 语句不够？（数据）=> {if（！data.isApproved) this.electronicInvoiceService.getElectronicInvoice(this.invoiceId).subscribe();}

Answer 1

其他订阅中的订阅不被视为 RxJs 中的最佳实践。

我认为更惯用的解决方案可能如下

this.electronicInvoiceService.getElectronicInvoice(this.invoiceId)
// here you start a pipe, i.e. a series of operations that transform the source stream
.pipe(
   // concatMap is the first operator which basically says: wait for upstream
   // to notify and then take the data notified and return a new Observable
   concatMap( data => {
      // here you put your if logic
      if (!data.isApproved) {
        // return the other Observable
        return this.electronicInvoiceStagingService.getElectronicInvoice(this.invoiceId)
      }
      // otherwise return EMPY, which is an Observable that does nothing and just
      // completes immediately
      return EMPTY
   })
)
// eventually you just subscribe to the one and only one stream you have created
// transforming, with the pipe, the original source stream
.subscribe(dataFromStagingService => {
   // do anything you need to do with the data returned by the staging service call
})

Angular RxJS - 只有当订阅另一个 Observable 给出特定结果时才订阅 Observable

Angular RxJS - Subscribe to Observable only IF subscribing to another Observable gave a certain result

observable

rxjs

angular