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There is a newer version: 2.0.0-rc-1

/*
 * Copyright 2014 the original author or authors.
 *
 * 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 ratpack.exec;

import ratpack.func.Action;

/**
 * A promise of an outcome that may be a successful result or an error exception.
 *
 * @param  The type of result object that the operation produces
 */
public interface Promise extends SuccessPromise {

  /**
   * Specifies the action to take if the an error occurs trying to produce the promised value.
   *
   * @param errorHandler the action to take if an error occurs
   * @return A promise for the successful result
   */
  SuccessPromise onError(Action errorHandler);

  /**
   * {@inheritDoc}
   */
  @Override
  void then(Action then);

}