/*******************************************************************************
* Copyright (c) 2005, 2015 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.core.commands.operations;
/**
* <p>
* This class is used to maintain the instance of the operation history that
* should be used by classes that access the undo or redo history and add
* undoable operations to the history.
*
* <p>
* It is intended that an application can create an operation history appropriate
* for its needs and set it into this class. Otherwise, a default operation history
* will be created. The operation history may only be set one time. All classes that
* access an operations history use this class to obtain the correct instance.
*
* @since 3.1
*/
public final class OperationHistoryFactory {
private static IOperationHistory operationHistory;
/**
* Return the operation history to be used for managing undoable operations.
*
* @return the operation history to be used for executing, undoing, and
* redoing operations.
*/
public static IOperationHistory getOperationHistory() {
if (operationHistory == null) {
operationHistory = new DefaultOperationHistory();
}
return operationHistory;
}
/**
* Set the operation history to be used for managing undoable operations.
* This method may only be called one time, and must be called before any
* request to get the history. Attempts to set the operation history will
* be ignored after it has been already set, or after a default one has
* been created.
*
* @param history
* the operation history to be used for executing, undoing, and
* redoing operations.
*/
public static void setOperationHistory(IOperationHistory history) {
// If one has already been set or created, ignore this request.
if (operationHistory == null) {
operationHistory = history;
}
}
private OperationHistoryFactory() {
// may not be instantiated
}
}