private void registerGcm() {
   chatApi
       .gcmRegister(Build.MODEL, null, appPreferences.getGcmId())
       .subscribeOn(Schedulers.io())
       .observeOn(AndroidSchedulers.mainThread())
       .subscribe(
           new Action1<Void>() {
             @Override
             public void call(Void aVoid) {
               appPreferences.setGcmRegistered(true);
             }
           },
           getOnError());
 }