Angular/RxJS:同步可观察 [英] Angular/RxJS: synchronous observable

问题描述

我有一个具有方法foo的服务.在方法内部，我订阅了一个可观察的(http客户端).

I have a service that has a method foo. Inside the method I subscribe to an observable (http-client).

foo () : boolean
{
  let ret : false;

  this.http.get ("/blabla").subscribe (
  (resp) =>
  {
    ret = true;
  }

  return ret;
);

我喜欢从foo返回一个布尔值，该值取决于get.这不起作用，因为http.get是异步的-在http.get完成之前调用return.

I like to return a boolean value from foo that depends on the get. That is not working because http.get is asynchrouns - return is called before http.get finished.

如何使它同步?

编辑

在这里不能选择返回observable布尔值. 那是因为我处理了get in foo的响应(此处未显示)，但是我还需要根据foo的返回采取行动.

Returning the observable instead boolean is not an option here. That is because I handle the response of get in foo (not shown here) but I also need to act out of foo depending of its return.

EDIT2

我用管子和水龙头扩展了样品.现在，我返回服务外部的http.get-observable，并用tap处理http.get-result.

I extended my sample with pipe and tap. Now I return the http.get-observable for outside the service and I process the http.get-result with tap.

foo () : Observable <any>
{
  return this.http.get ("/blabla").pipe (tap (x => handlehere ()));
}

据我所知，它只有一个丑陋之处.我有解析foo内部和外部的get-result的复杂性.我希望在foo之外使用一个简单的布尔值.

As far I see there is only one uglyness with it. I have the complexity of parsing the get-result inside AND outside of foo. I would prefer a simple boolean outside of foo.

推荐答案

此方法只能异步运行，因此您没有太多选择.退回烦人并订阅或退回诺言.也许，答应诺言会在理解方面满足您的更多需求.

This method can only run asynchronously so you don't have a lot of option. Returning the obsersable and subscribe or return a promise. Perhaps returning a Promise will suite more your need in term of comprehention.

为您服务:foo方法:

In your service : the foo method :

async foo() {
   const result = await this.http.get("/blabla").toPromise();

   // do what you want with result 

   return result;
}

如何命名:

this.myService.foo().then( (result) => {
   // Do what you want with the result
});

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