RealmObjectObservable.java

/* Copyright 2016 iMykolaPro
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. */

/**
 * Example of usage:
 * *** Was:
 * public Observable<T> query(Class<T> clazz, String fieldName, long value) {     
 *    return getRealmAsObservable(clazz)
 *            .flatMap(realm -> 
 *              RealmObject.asObservable(
 *                realm.where(clazz)
 *                .equalTo(fieldName, value)
 *                .findFirstAsync()
 *              )
 *            .filter(RealmObject::isLoaded)
 *            .doOnUnsubscribe(realm::close));
 * }
 * *** Became:
 * public Observable<T> query(Class<T> clazz, String fieldName, long value) {
 *    return getRealmAsObservable2(clazz)
 *      .flatMap(realm ->
 *        RealmObjectObservable.from(
 *          realm.where(clazz)
 *            .equalTo(fieldName, value)
 *            .findFirstAsync()
 *        )
 *      .filter(RealmObject::isLoaded)
 *      .doOnDispose(realm::close));
 * }
 */

public class RealmObjectObservable<T extends RealmModel> implements
    ObservableOnSubscribe<T> {

  public static <T extends RealmModel> Observable<T> from(@NonNull T object) {
    return Observable.create(new RealmObjectObservable<T>(object));
  }

  private final T object;

  private RealmObjectObservable(@NonNull T object) {
    this.object = object;
  }

  @Override
  public void subscribe(ObservableEmitter<T> emitter) throws Exception {
    // Initial element
    emitter.onNext(object);

    RealmChangeListener<T> changeListener = new RealmChangeListener<T>() {
      @Override
      public void onChange(T element) {
        emitter.onNext(element);
      }
    };

    RealmObject.addChangeListener(object, changeListener);

    emitter.setCancellable(new Cancellable() {
      @Override
      public void cancel() throws Exception {
        RealmObject.removeChangeListener(object, changeListener);
      }
    });
  }
}