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Reactive Extensions for Java

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/**
 * 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.maybe;

import io.reactivex.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.internal.disposables.EmptyDisposable;
import io.reactivex.internal.functions.ObjectHelper;

/**
 * Calls a MaybeOperator for the incoming MaybeObserver.
 *
 * @param  the upstream value type
 * @param  the downstream value type
 */
public final class MaybeLift extends AbstractMaybeWithUpstream {

    final MaybeOperator operator;

    public MaybeLift(MaybeSource source, MaybeOperator operator) {
        super(source);
        this.operator = operator;
    }

    @Override
    protected void subscribeActual(MaybeObserver observer) {
        MaybeObserver lifted;

        try {
            lifted = ObjectHelper.requireNonNull(operator.apply(observer), "The operator returned a null MaybeObserver");
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            EmptyDisposable.error(ex, observer);
            return;
        }

        source.subscribe(lifted);
    }
}