/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.internal.operators.observable;
import java.util.concurrent.
Callable;
import io.reactivex.*;
import io.reactivex.exceptions.
Exceptions;
import io.reactivex.functions.
BiFunction;
import io.reactivex.internal.disposables.
EmptyDisposable;
import io.reactivex.internal.functions.
ObjectHelper;
import io.reactivex.internal.operators.observable.
ObservableReduceSeedSingle.
ReduceSeedObserver;
/**
* Reduce a sequence of values, starting from a generated seed value and by using
* an accumulator function and return the last accumulated value.
*
* @param <T> the source value type
* @param <R> the accumulated result type
*/
public final class
ObservableReduceWithSingle<T, R> extends
Single<R> {
final
ObservableSource<T>
source;
final
Callable<R>
seedSupplier;
final
BiFunction<R, ? super T, R>
reducer;
public
ObservableReduceWithSingle(
ObservableSource<T>
source,
Callable<R>
seedSupplier,
BiFunction<R, ? super T, R>
reducer) {
this.
source =
source;
this.
seedSupplier =
seedSupplier;
this.
reducer =
reducer;
}
@
Override
protected void
subscribeActual(
SingleObserver<? super R>
observer) {
R
seed;
try {
seed =
ObjectHelper.
requireNonNull(
seedSupplier.
call(), "The seedSupplier returned a null value");
} catch (
Throwable ex) {
Exceptions.
throwIfFatal(
ex);
EmptyDisposable.
error(
ex,
observer);
return;
}
source.
subscribe(new
ReduceSeedObserver<T, R>(
observer,
reducer,
seed));
}
}