ObjectUndoContext


1   /*******************************************************************************
2    * Copyright (c) 2005, 2006 IBM Corporation and others.
3    * All rights reserved. This program and the accompanying materials
4    * are made available under the terms of the Eclipse Public License v1.0
5    * which accompanies this distribution, and is available at
6    * http://www.eclipse.org/legal/epl-v10.html
7    *
8    * Contributors:
9    *     IBM Corporation - initial API and implementation
10   *******************************************************************************/
11  package org.eclipse.core.commands.operations;
12  
13  import java.util.ArrayList  ;
14  import java.util.List  ;
15  
16  /**
17   * <p>
18   * An undo context that can be used to represent any given object. Clients
19   * can add matching contexts to this context.  This class may be instantiated
20   * by clients.
21   * </p>
22   * 
23   * @since 3.1
24   */
25  public final class ObjectUndoContext extends UndoContext {
26  
27      private Object   object;
28  
29      private String   label;
30  
31      private List   children = new ArrayList  ();
32  
33      /**
34       * Construct an operation context that represents the given object.
35       * 
36       * @param object 
37       *            the object to be represented.
38       */
39      public ObjectUndoContext(Object   object) {
40          this(object, null);
41      }
42  
43      /**
44       * Construct an operation context that represents the given object and has a
45       * specialized label.
46       * 
47       * @param object 
48       *            the object to be represented.
49       * @param label 
50       *            the label for the context
51       */
52      public ObjectUndoContext(Object   object, String   label) {
53          super();
54          this.object = object;
55          this.label = label;
56      }
57  
58      /*
59       * (non-Javadoc)
60       * 
61       * @see org.eclipse.core.commands.operations.IUndoContext#getLabel()
62       */
63      public String   getLabel() {
64          if (label != null) {
65              return label;
66          }
67          if (object != null) {
68              return object.toString();
69          }
70          return super.getLabel();
71      }
72  
73      /**
74       * Return the object that is represented by this context.
75       * 
76       * @return the object represented by this context.
77       */
78      public Object   getObject() {
79          return object;
80      }
81  
82      /**
83       * Add the specified context as a match of this context. Contexts added as
84       * matches of this context will be interpreted as a match of this context
85       * when the history is filtered for a particular context. Adding a match
86       * allows components to create their own contexts for implementing
87       * specialized behavior, yet have their operations appear in a more
88       * global context.
89       * 
90       * @param context 
91       *            the context to be added as a match of this context
92       */
93      public void addMatch(IUndoContext context) {
94          children.add(context);
95      }
96  
97      /**
98       * Remove the specified context as a match of this context. The context will
99       * no longer be interpreted as a match of this context when the history is
100      * filtered for a particular context. This method has no effect if the
101      * specified context was never previously added as a match.
102      * 
103      * @param context 
104      *            the context to be removed from the list of matches for this
105      *            context
106      */
107     public void removeMatch(IUndoContext context) {
108         children.remove(context);
109     }
110 
111     /*
112      * (non-Javadoc)
113      * 
114      * @see org.eclipse.core.commands.operations.IUndoContext#matches(IUndoContext
115      *      context)
116      */
117     public boolean matches(IUndoContext context) {
118         // Check first for explicit matches that have been assigned.
119         if (children.contains(context)) {
120             return true;
121         }
122         // Contexts for equal objects are considered matching
123         if (context instanceof ObjectUndoContext && getObject() != null) {
124             return getObject().equals(((ObjectUndoContext)context).getObject());
125         }
126         // Use the normal matching implementation
127         return super.matches(context);
128     }
129     
130     /**
131      * The string representation of this operation.  Used for debugging purposes only.
132      * This string should not be shown to an end user.
133      * 
134      * @return The string representation.
135      */
136     public String   toString() {
137         return getLabel();
138     }
139 
140 
141 }
142
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