Realm на Android: разделяйте логику БД

public class RealmController {
    private static RealmController instance;
    private final Realm realm;
    private ServiceInterface restInterface;
    private final String TAG = "RealmController";

    private static boolean browseFetchAllowed = true;

    private RealmConfiguration config = new RealmConfiguration.Builder()
            .name("myRealm")
            .schemaVersion(0)
            .deleteRealmIfMigrationNeeded()
            .build();

    public RealmController(Application application) {
        restInterface =  ServiceGenerator.createService(ServiceInterface.class);
        realm = Realm.getInstance(config);
    }

    public void setAuthentication(String token, String uid) {
        this.restInterface = ServiceGenerator.createService(ServiceInterface.class, token, uid);
    }

    public static RealmController with(Fragment fragment) {

        if (instance == null) {
            instance = new RealmController(fragment.getActivity().getApplication());
        }
        return instance;
    }

    public static RealmController with(Activity activity) {

        if (instance == null) {
            instance = new RealmController(activity.getApplication());
        }
        return instance;
    }

    public static RealmController with(Application application) {

        if (instance == null) {
            instance = new RealmController(application);
        }
        return instance;
    }

    public RealmController getInstance() {

        return instance;
    }

    public ServiceInterface getRestInterface() {
        return restInterface;
    }

    public Realm getRealm() {
        return realm;
    }
    
    public RealmResults<MyRealmObject> getStuff() {
        return realm.where(MyRealObject.class).findAll();
    }
    
    public void setStuff(RealmList<MyRealmObject> stuff) {
        realm.beginTransaction();
        realm.copyToRealmOrUpdate(stuff);
        realm.commitTransaction();
    }
    
    public void getStuffFromServer() {
        
        restInterface.getStuff().enqueue(new Callback<RealmList<MyRealmObject>>() {
            @Override
            public void onResponse(Call<RealmList<MyRealmObject>> call, Response<RealmList<MyRealmObject>> response) {
                if (response.isSuccessful()) {
                    realm.beginTransaction();
                    realm.copyToRealmOrUpdate(response.body);
                    realm.commitTransaction();
                }
            }

            @Override
            public void onFailure(Call<RealmList<RealmAd>> call, Throwable t) {
                t.printStackTrace();
            }
        });
    }
}