rxjs - Angular 2 : merge several http calls into one -

i have service used upload pictures. upload picture,

return this.http.post(/* ... */) 

and subscription can subscribe in component. when want upload several pictures, have

for (let p of pics) { this.http.post(/* ... */); } 

my problem return results of all calls instead of 1 call. possible ?

edit here service

addpictures(files: file[], folder: string): observable<parse.object[]> {   let haserror = false;   (let file of files) {     let [type, ext] = file.type.split('/');     if (type.tolowercase() !== 'image' || !environment.imgexts.includes(ext.tolowercase())) { haserror = true; }   }   if (haserror) { return observable.throw('invalid extension detected'); }    let observables: observable<parse.object>[] = [];    (let file of files) {     // size     let img = new image();     img.onload = () => {       // create parse document       let parseimg = { url: '', type: file.type, width: img.width, height: img.height };       // upload on amazon , add db       observables.push(this.addpicture(parseimg, file, folder));     }     img.src = window.url.createobjecturl(file);   }   return observable.forkjoin(observables); } 

if want run requests in parallel can use forkjoin():

const observables = pics.map(p => this.http.post(/* ... */));  observable.forkjoin(observables)   .subscribe(results => ...); 

you use observable.merge() receive results arrive or observable.concat() call requests 1 after another.

maybe have @ sending multiple parallel http requests , sending multiple sequential http requests