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Storage Repository Pattern for MongoDB, Cassandra, Redis, etc.

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/*
    Copyright 2012, Strategic Gains, 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 com.strategicgains.repoexpress.util;

import java.util.Iterator;

import com.strategicgains.repoexpress.domain.Identifiable;
import com.strategicgains.repoexpress.domain.Identifier;


/**
 * Returns an IdentifierIterator, which iterates over the identifiers of the Identifiable instances.
 * The returned iterator iterates the string IDs of the underlying instances--instead of the
 * instances themselves.
 * 
 * This means, that if you have a Collection of Identifiable instances, you can get an iterator
 * over the IDs of those Identifiable guys.  This is useful when creating queries and such using,
 * say the "in" operator.
 * 
 * For example (psuedo-code):

 * List blogEntries = ... // list of blog entries we're deleting.

 * blogCommentsRepository.delete().where("blogEntryId").isIn(new IdentifiableIterable(blogEntries));
 * 
 * @author toddf
 * @since Oct 25, 2012
 */
public class IdentifiableIterable
implements Iterable
{
	private Iterable iterable;

	public IdentifiableIterable(Iterable iterable)
	{
		this.iterable = iterable;
	}

	@Override
	public Iterator iterator()
	{
		return new IdentifierIterator(iterable);
	}
}