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Merge pull request ReactiveX#362 from benjchristensen/operator-first-…
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rxjava-core/src/main/java/rx/operators/OperationFirstOrDefault.java
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/** | ||
* Copyright 2013 Netflix, Inc. | ||
* | ||
* 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. | ||
*/ | ||
package rx.operators; | ||
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import static org.mockito.Matchers.*; | ||
import static org.mockito.Mockito.*; | ||
import static org.mockito.MockitoAnnotations.initMocks; | ||
import static rx.Observable.create; | ||
import static rx.Observable.empty; | ||
import static rx.Observable.from; | ||
import static rx.util.functions.Functions.alwaysTrue; | ||
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import java.util.concurrent.atomic.AtomicBoolean; | ||
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import org.junit.Before; | ||
import org.junit.Test; | ||
import org.mockito.Mock; | ||
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import rx.Observable; | ||
import rx.Observable.OnSubscribeFunc; | ||
import rx.Observer; | ||
import rx.Subscription; | ||
import rx.subscriptions.Subscriptions; | ||
import rx.util.functions.Action0; | ||
import rx.util.functions.Func1; | ||
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/** | ||
* Returns an Observable that emits the first item emitted by the source | ||
* Observable, or a default value if the source emits nothing. | ||
*/ | ||
public final class OperationFirstOrDefault { | ||
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/** | ||
* Returns an Observable that emits the first item emitted by the source | ||
* Observable that satisfies the given condition, | ||
* or a default value if the source emits no items that satisfy the given condition. | ||
* | ||
* @param source | ||
* The source Observable to emit the first item for. | ||
* @param predicate | ||
* The condition the emitted source items have to satisfy. | ||
* @param defaultValue | ||
* The default value to use whenever the source Observable doesn't emit anything. | ||
* @return A subscription function for creating the target Observable. | ||
*/ | ||
public static <T> OnSubscribeFunc<T> firstOrDefault(Observable<? extends T> source, Func1<? super T, Boolean> predicate, T defaultValue) { | ||
return new FirstOrElse<T>(source, predicate, defaultValue); | ||
} | ||
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/** | ||
* Returns an Observable that emits the first item emitted by the source | ||
* Observable, or a default value if the source emits nothing. | ||
* | ||
* @param source | ||
* The source Observable to emit the first item for. | ||
* @param defaultValue | ||
* The default value to use whenever the source Observable doesn't emit anything. | ||
* @return A subscription function for creating the target Observable. | ||
*/ | ||
public static <T> OnSubscribeFunc<T> firstOrDefault(Observable<? extends T> source, T defaultValue) { | ||
return new FirstOrElse<T>(source, alwaysTrue(), defaultValue); | ||
} | ||
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private static class FirstOrElse<T> implements OnSubscribeFunc<T> { | ||
private final Observable<? extends T> source; | ||
private final Func1<? super T, Boolean> predicate; | ||
private final T defaultValue; | ||
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private FirstOrElse(Observable<? extends T> source, Func1<? super T, Boolean> predicate, T defaultValue) { | ||
this.source = source; | ||
this.defaultValue = defaultValue; | ||
this.predicate = predicate; | ||
} | ||
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@Override | ||
public Subscription onSubscribe(final Observer<? super T> observer) { | ||
final Subscription sourceSub = source.subscribe(new Observer<T>() { | ||
private final AtomicBoolean hasEmitted = new AtomicBoolean(false); | ||
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@Override | ||
public void onCompleted() { | ||
if (!hasEmitted.get()) { | ||
observer.onNext(defaultValue); | ||
observer.onCompleted(); | ||
} | ||
} | ||
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@Override | ||
public void onError(Throwable e) { | ||
observer.onError(e); | ||
} | ||
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@Override | ||
public void onNext(T next) { | ||
try { | ||
if (!hasEmitted.get() && predicate.call(next)) { | ||
hasEmitted.set(true); | ||
observer.onNext(next); | ||
observer.onCompleted(); | ||
} | ||
} catch (Throwable t) { | ||
// may happen within the predicate call (user code) | ||
observer.onError(t); | ||
} | ||
} | ||
}); | ||
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return Subscriptions.create(new Action0() { | ||
@Override | ||
public void call() { | ||
sourceSub.unsubscribe(); | ||
} | ||
}); | ||
} | ||
} | ||
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public static class UnitTest { | ||
@Mock | ||
Observer<? super String> w; | ||
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private static final Func1<String, Boolean> IS_D = new Func1<String, Boolean>() { | ||
@Override | ||
public Boolean call(String value) { | ||
return "d".equals(value); | ||
} | ||
}; | ||
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@Before | ||
public void before() { | ||
initMocks(this); | ||
} | ||
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@Test | ||
public void testFirstOrElseOfNone() { | ||
Observable<String> src = empty(); | ||
create(firstOrDefault(src, "default")).subscribe(w); | ||
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verify(w, times(1)).onNext(anyString()); | ||
verify(w, times(1)).onNext("default"); | ||
verify(w, never()).onError(any(Throwable.class)); | ||
verify(w, times(1)).onCompleted(); | ||
} | ||
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@Test | ||
public void testFirstOrElseOfSome() { | ||
Observable<String> src = from("a", "b", "c"); | ||
create(firstOrDefault(src, "default")).subscribe(w); | ||
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verify(w, times(1)).onNext(anyString()); | ||
verify(w, times(1)).onNext("a"); | ||
verify(w, never()).onError(any(Throwable.class)); | ||
verify(w, times(1)).onCompleted(); | ||
} | ||
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@Test | ||
public void testFirstOrElseWithPredicateOfNoneMatchingThePredicate() { | ||
Observable<String> src = from("a", "b", "c"); | ||
create(firstOrDefault(src, IS_D, "default")).subscribe(w); | ||
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verify(w, times(1)).onNext(anyString()); | ||
verify(w, times(1)).onNext("default"); | ||
verify(w, never()).onError(any(Throwable.class)); | ||
verify(w, times(1)).onCompleted(); | ||
} | ||
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@Test | ||
public void testFirstOrElseWithPredicateOfSome() { | ||
Observable<String> src = from("a", "b", "c", "d", "e", "f"); | ||
create(firstOrDefault(src, IS_D, "default")).subscribe(w); | ||
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verify(w, times(1)).onNext(anyString()); | ||
verify(w, times(1)).onNext("d"); | ||
verify(w, never()).onError(any(Throwable.class)); | ||
verify(w, times(1)).onCompleted(); | ||
} | ||
} | ||
} |
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/** | ||
* Copyright 2013 Netflix, Inc. | ||
* | ||
* 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. | ||
*/ | ||
package rx.util.functions; | ||
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/** | ||
* Implements the negation of a predicate. | ||
* | ||
* @param <T> The type of the single input parameter. | ||
*/ | ||
public class Not<T> implements Func1<T, Boolean> { | ||
private final Func1<? super T, Boolean> predicate; | ||
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/** | ||
* Constructs a predicate that returns true for each input that the source | ||
* predicate returns false for and vice versa. | ||
* | ||
* @param predicate The source predicate to negate. | ||
*/ | ||
public Not(Func1<? super T, Boolean> predicate) { | ||
this.predicate = predicate; | ||
} | ||
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@Override | ||
public Boolean call(T param) { | ||
return !predicate.call(param); | ||
} | ||
} |
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