RxJs Observables 使用 takeUntil 嵌套订阅

Question

我该如何摆脱这些嵌套订阅？我想使用 concatMap 或 mergeMap 来做到这一点 - 如果您同意，我如何处理与外部订阅不同的内部订阅的 takeUntil ？我对操作符和 RxJ 还很陌生。

this.myService.selectedCustomerId
.pipe(
    takeUntil(this.unsubscribe),
).subscribe((customerId: number) => {
    // Do some stuff...

    this.anotherService.hasPermission("ROLE1", customerId).pipe(
        takeUntil(this.cancel),
    ).subscribe(hasPermission => this.hasPermissionForRole1 = hasPermission);

    this.anotherService.hasPermission("ROLE2", customerId).pipe(
        takeUntil(this.cancel),
    ).subscribe(hasPermission => this.hasPermissionForRole2 = hasPermission);

    this.anotherService.hasPermission("ROLE3", customerId).pipe(
        takeUntil(this.cancel),
    ).subscribe(hasPermission => this.hasPermissionForRole3 = hasPermission);
  }
);

Answer 1

你可以这样实现：

this.myService.selectedCustomerId
    .pipe(
        takeUntil(this.unsubscribe),
        mergeMap(customerId: number) => {
            const roles = ["ROLE1", "ROLE2", "ROLE3"];
            return forkJoin(
                roles.map(role => this.anotherService.hasPermission(role, customerId))
            )
        }
    ).subscribe(([role1, role2, role3]) => {
        // Do some stuff...
        
    }