/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.waveprotocol.wave.model.document;
/**
* Bridge class to take care of some of the more annoying type conversion
* related to documents.
*
* NOTE(user): This two-step unravelling of re-quantifying the
* type-parameters into type variables is only required in order to coax
* javac's dumb generic-inference to realise that the call is type-safe.
* Eclipse's compiler is smarter, and does not require this extra work.
*
*/
public final class DocumentUnwrapper {
/** Helper interface that encapsulates an action */
public interface Action<R> {
/** Method to make use of the revised type */
<N, E extends N, T extends N> R handle(MutableDocument<N, E, T> doc);
}
/**
* Invoke the supplied action on an appropriately typed document
*
* @param action The action object to invoke
* @param doc The document to apply the action to
* @return The result of performing the action.
*/
public static <R, N> R invoke(Action<R> action, MutableDocument<N, ?, ?> doc) {
return action.handle(doc);
}
/** private constructor */
private DocumentUnwrapper() {
}
}