如何在第一个正在运行的订阅中以角度 6 同步使用第二个订阅返回值？

Question

I am using angular 6 app. In my case I have a one situation, in which I have to call another API and take data and then pass to first API and then resume API.

For example, in .ts file:

logout(){
  this.apiService.POST({}, "logout").subscribe((response: any) => 
  {
      alert("Logout subscribed returns...");
  }
}

In api.service.ts file:

POST(param, apiName) {
     var URL = Config.POST_ENDPOINT_URL + apiName; // Make whole API string
    
     return this.http.post(URL, param, options)
       .map(data => {
             // Hear I have to call another HTTP API call 
             // if I got specific status code in data. 
             var apiRes: any = data;
            
             if(apiRes.code == 500){
                   // Hear I need to call another API call 
                   this.another()subscribe((anotherResponse) => {
                      console.log("anotherResponse :::" , anotherResponse);

                   // Now the main issue is come in picture. I need data form

                   // anotherRespose and pass in POST to continue API call. 

                   // In short , I need to again call POST function with new data. 
                   })
             }

       });
     
}


another(): Observable<any> {
    return this.http.post(URL, obj, options)
      .map(data => {          
        alert("another data return...");
        return data;  // Need to pass this data
      })
}

In addition, when I call logout() it will return it's subscribed while another() is running. So, I need to set my flow in a sync.

Answer 1

Try this

POST(param, apiName) {

 return new Observable<number>(observer => {

    var URL = Config.POST_ENDPOINT_URL + apiName; // Make whole API string

    this.http.post(URL, param, options)
        .subscribe(data => {
            // Hear I have to call another HTTP API call 
            // if I got specific status code in data. 
            var apiRes: any = data;

            if(apiRes.code == 500){
                // Hear I need to call another API call 
                this.another()subscribe((anotherResponse) => {
                    console.log("anotherResponse :::" , anotherResponse);

                    observer.next(anotherResponse);
                    observer.complete();
                })
            }

   });

 }

}

Answer 2

You can use the switchMap operator by rxjs. You can do it like this:

this.http.post(url, param, options).pipe(
  switchMap(data => {
    this.another(); //where data is the response from your http post request
  })
);