TextEditVisitor


1   /*******************************************************************************
2    * Copyright (c) 2000, 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.text.edits;
12  
13  /**
14   * A visitor for text edits.
15   * <p>
16   * For each different concrete text edit type <it>T</it> there is a method:
17   * <ul>
18   *   <li><code>public boolean visit(<it>T</it> node)</code> - Visits the given edit to
19   *   perform some arbitrary operation. If <code>true </code> is returned, the given edit's
20   *   child edits will be visited next; however, if <code>false</code> is returned, the
21   *   given edit's child edits will not be visited. The default implementation provided by
22   *   this class calls a generic method <code>visitNode(<it>TextEdit</it> node)</code>.
23   *   Subclasses may reimplement these method as needed.</li>
24   * </ul>
25   * </p>
26   * <p>
27   * In addition, there are methods for visiting text edits in the
28   * abstract, regardless of node type:
29   * <ul>
30   *   <li><code>public void preVisit(TextEdit edit)</code> - Visits
31   *   the given edit to perform some arbitrary operation.
32   *   This method is invoked prior to the appropriate type-specific
33   *   <code>visit</code> method.
34   *   The default implementation of this method does nothing.
35   *   Subclasses may reimplement this method as needed.</li>
36   *
37   *   <li><code>public void postVisit(TextEdit edit)</code> - Visits
38   *   the given edit to perform some arbitrary operation.
39   *   This method is invoked after the appropriate type-specific
40   *   <code>endVisit</code> method.
41   *   The default implementation of this method does nothing.
42   *   Subclasses may reimplement this method as needed.</li>
43   * </ul>
44   * </p>
45   * <p>
46   * For edits with children, the child nodes are visited in increasing order.
47   * </p>
48   *
49   * @see TextEdit#accept(TextEditVisitor)
50   * @since 3.0
51   */
52  public class TextEditVisitor {
53  
54      /**
55       * Visits the given text edit prior to the type-specific visit.
56       * (before <code>visit</code>).
57       * <p>
58       * The default implementation does nothing. Subclasses may reimplement.
59       * </p>
60       *
61       * @param edit the node to visit
62       */
63      public void preVisit(TextEdit edit) {
64          // default implementation: do nothing
65      }
66  
67      /**
68       * Visits the given text edit following the type-specific visit
69       * (after <code>endVisit</code>).
70       * <p>
71       * The default implementation does nothing. Subclasses may reimplement.
72       * </p>
73       *
74       * @param edit the node to visit
75       */
76      public void postVisit(TextEdit edit) {
77          // default implementation: do nothing
78      }
79  
80      /**
81       * Visits the given text edit. This method is called by default from
82       * type-specific visits. It is not called by an edit's accept method.
83       * The default implementation returns <code>true</code>.
84       *
85       * @param edit the node to visit
86       * @return If <code>true</code> is returned, the given node's child
87       *  nodes will be visited next; however, if <code>false</code> is
88       *  returned, the given node's child nodes will not be visited.
89       */
90      public boolean visitNode(TextEdit edit) {
91          return true;
92      }
93  
94      /**
95       * Visits a <code>CopySourceEdit</code> instance.
96       *
97       * @param edit the node to visit
98       * @return If <code>true</code> is returned, the given node's child
99       *  nodes will be visited next; however, if <code>false</code> is
100      *  returned, the given node's child nodes will not be visited.
101      */
102     public boolean visit(CopySourceEdit edit) {
103         return visitNode(edit);
104     }
105 
106     /**
107      * Visits a <code>CopyTargetEdit</code> instance.
108      *
109      * @param edit the node to visit
110      * @return If <code>true</code> is returned, the given node's child
111      *  nodes will be visited next; however, if <code>false</code> is
112      *  returned, the given node's child nodes will not be visited.
113      */
114     public boolean visit(CopyTargetEdit edit) {
115         return visitNode(edit);
116     }
117 
118     /**
119      * Visits a <code>MoveSourceEdit</code> instance.
120      *
121      * @param edit the node to visit
122      * @return If <code>true</code> is returned, the given node's child
123      *  nodes will be visited next; however, if <code>false</code> is
124      *  returned, the given node's child nodes will not be visited.
125      */
126     public boolean visit(MoveSourceEdit edit) {
127         return visitNode(edit);
128     }
129 
130     /**
131      * Visits a <code>MoveTargetEdit</code> instance.
132      *
133      * @param edit the node to visit
134      * @return If <code>true</code> is returned, the given node's child
135      *  nodes will be visited next; however, if <code>false</code> is
136      *  returned, the given node's child nodes will not be visited.
137      */
138     public boolean visit(MoveTargetEdit edit) {
139         return visitNode(edit);
140     }
141 
142     /**
143      * Visits a <code>RangeMarker</code> instance.
144      *
145      * @param edit the node to visit
146      * @return If <code>true</code> is returned, the given node's child
147      *  nodes will be visited next; however, if <code>false</code> is
148      *  returned, the given node's child nodes will not be visited.
149      */
150     public boolean visit(RangeMarker edit) {
151         return visitNode(edit);
152     }
153 
154     /**
155      * Visits a <code>CopyingRangeMarker</code> instance.
156      *
157      * @param edit the node to visit
158      * @return If <code>true</code> is returned, the given node's child
159      *  nodes will be visited next; however, if <code>false</code> is
160      *  returned, the given node's child nodes will not be visited.
161      */
162     public boolean visit(CopyingRangeMarker edit) {
163         return visitNode(edit);
164     }
165 
166     /**
167      * Visits a <code>DeleteEdit</code> instance.
168      *
169      * @param edit the node to visit
170      * @return If <code>true</code> is returned, the given node's child
171      *  nodes will be visited next; however, if <code>false</code> is
172      *  returned, the given node's child nodes will not be visited.
173      */
174     public boolean visit(DeleteEdit edit) {
175         return visitNode(edit);
176     }
177 
178     /**
179      * Visits a <code>InsertEdit</code> instance.
180      *
181      * @param edit the node to visit
182      * @return If <code>true</code> is returned, the given node's child
183      *  nodes will be visited next; however, if <code>false</code> is
184      *  returned, the given node's child nodes will not be visited.
185      */
186     public boolean visit(InsertEdit edit) {
187         return visitNode(edit);
188     }
189 
190     /**
191      * Visits a <code>ReplaceEdit</code> instance.
192      *
193      * @param edit the node to visit
194      * @return If <code>true</code> is returned, the given node's child
195      *  nodes will be visited next; however, if <code>false</code> is
196      *  returned, the given node's child nodes will not be visited.
197      */
198     public boolean visit(ReplaceEdit edit) {
199         return visitNode(edit);
200     }
201 
202     /**
203      * Visits a <code>UndoEdit</code> instance.
204      *
205      * @param edit the node to visit
206      * @return If <code>true</code> is returned, the given node's child
207      *  nodes will be visited next; however, if <code>false</code> is
208      *  returned, the given node's child nodes will not be visited.
209      */
210     public boolean visit(UndoEdit edit) {
211         return visitNode(edit);
212     }
213 
214     /**
215      * Visits a <code>MultiTextEdit</code> instance.
216      *
217      * @param edit the node to visit
218      * @return If <code>true</code> is returned, the given node's child
219      *  nodes will be visited next; however, if <code>false</code> is
220      *  returned, the given node's child nodes will not be visited.
221      */
222     public boolean visit(MultiTextEdit edit) {
223         return visitNode(edit);
224     }
225 }
226
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