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rxjava2-backport developed by David Karnok

There is a newer version: 2.0.0-RC3

/**
 * Copyright 2015 David Karnok and 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 hu.akarnokd.rxjava2.internal.operators;

import org.reactivestreams.*;

import hu.akarnokd.rxjava2.Observable;
import hu.akarnokd.rxjava2.functions.Function;
import hu.akarnokd.rxjava2.internal.subscriptions.*;

/**
 * Represents a constant scalar value.
 * @param  the value type
 */
public final class ObservableScalarSource extends Observable {
    private final T value;
    public ObservableScalarSource(final T value) {
        super(new Publisher() {
            @Override
            public void subscribe(Subscriber s) {
                s.onSubscribe(new ScalarSubscription(s, value));
            }
        });
        this.value = value;
    }
    
    public T value() {
        return value;
    }
    
    public  Publisher scalarFlatMap(final Function> mapper) {
        return new Publisher() {
            @Override
            public void subscribe(Subscriber s) {
                Publisher other;
                try {
                    other = mapper.apply(value);
                } catch (Throwable e) {
                    EmptySubscription.error(e, s);
                    return;
                }
                if (other == null) {
                    EmptySubscription.error(new NullPointerException("The publisher returned by the function is null"), s);
                    return;
                }
                other.subscribe(s);
            }
        };
    }
}