NG2- Observables - Subject js- promises

NG2- Observables - Subject js- promises
=============================
components.ts
--------------
import { Subject } from 'rxjs';

export class Mycomponents {

postCall = new Subject();

this.checkPostisTrue(getChecklist);   // once it returns true
this.postCustomGroup(postdata);        // then it should execute. wait until $ deffered


checkPostisTrue(data){

this._MyService.checkPost(data).subscribe( (data:any) => {   // get service method
if(data == true){   //someother condition
this.postCall.next(true);   // true is passing data. May be array any,string type

}
}
}

postCustomGroup(post){
this._MyService.PostPromiseData(data).subscribe( (data:any) => { 

}


}


}