Model


1   /*******************************************************************************
2    * Copyright (c) 2004, 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.ui.internal;
12  
13  import java.util.ArrayList  ;
14  import java.util.Iterator  ;
15  import java.util.List  ;
16  
17  /**
18   * Represents an object with state that will notifies a set of listeners
19   * whenever its state changes 
20   */
21  public class Model {
22  
23      /**
24       * Current state of the model
25       */
26      private Object   state;
27  
28      /**
29       * Set of objects that will be notified about state changes
30       */
31      private List   views = new ArrayList  (1);
32  
33      /**
34       * Creates a new model with the given initial state.
35       * 
36       * @param initialState
37       */
38      public Model(Object   initialState) {
39          state = initialState;
40      }
41  
42      /**
43       * Returns the current state of the model.
44       * 
45       * @return the current model state
46       */
47      public Object   getState() {
48          return state;
49      }
50  
51      /**
52       * Sets the current state of the model.
53       * 
54       * @param newState the new state of the model
55       * @param toOmit change listener that should be omitted from change notifications (or null if all
56       * listeners should be notified). 
57       */
58      public void setState(Object   newState, IChangeListener toOmit) {
59          if (areEqual(newState, state)) {
60              return;
61          }
62  
63          state = newState;
64  
65          Iterator   iter = views.iterator();
66          while (iter.hasNext()) {
67              IChangeListener next = (IChangeListener) iter.next();
68  
69              if (next != toOmit) {
70                  next.update(true);
71              }
72          }
73      }
74  
75      private boolean areEqual(Object   o1, Object   o2) {
76          if (o1 == null) {
77              return o2 == null;
78          }
79          if (o2 == null) {
80              return false;
81          }
82  
83          return o1.equals(o2);
84      }
85  
86      /**
87       * Adds the given listener to the set of listeners that will be
88       * notified when the state changes. 
89       * 
90       * @param toAdd
91       */
92      public void addChangeListener(IChangeListener changeListener) {
93          changeListener.update(false);
94          views.add(changeListener);
95      }
96  
97      /**
98       * Stops this model from sending change events from the given listener.
99       * 
100      * @param toRemove
101      */
102     public void removeChangeListener(IChangeListener changeListener) {
103         views.remove(changeListener);
104     }
105 
106 }
107
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