FieldAccess


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  
12  package org.eclipse.jdt.core.dom;
13  
14  import java.util.ArrayList  ;
15  import java.util.List  ;
16  
17  /**
18   * Field access expression AST node type.
19   *
20   * <pre>
21   * FieldAccess: 
22   *      Expression <b>.</b> Identifier
23   * </pre>
24   * 
25   * <p>
26   * Note that there are several kinds of expressions that resemble field access
27   * expressions: qualified names, this expressions, and super field access
28   * expressions. The following guidelines help with correct usage:
29   * <ul>
30   *   <li>An expression like "foo.this" can only be represented as a this
31   *   expression (<code>ThisExpression</code>) containing a simple name.
32   *   "this" is a keyword, and therefore invalid as an identifier.</li>
33   *   <li>An expression like "this.foo" can only be represented as a field
34   *   access expression (<code>FieldAccess</code>) containing a this expression
35   *   and a simple name. Again, this is because "this" is a keyword, and
36   *   therefore invalid as an identifier.</li>
37   *   <li>An expression with "super" can only be represented as a super field
38   *   access expression (<code>SuperFieldAccess</code>). "super" is a also
39   *   keyword, and therefore invalid as an identifier.</li>
40   *   <li>An expression like "foo.bar" can be represented either as a
41   *   qualified name (<code>QualifiedName</code>) or as a field access
42   *   expression (<code>FieldAccess</code>) containing simple names. Either
43   *   is acceptable, and there is no way to choose between them without
44   *   information about what the names resolve to
45   *   (<code>ASTParser</code> may return either).</li>
46   *   <li>Other expressions ending in an identifier, such as "foo().bar" can
47   *   only be represented as field access expressions
48   *   (<code>FieldAccess</code>).</li>
49   * </ul>
50   * </p>
51   * 
52   * @see QualifiedName
53   * @see ThisExpression
54   * @see SuperFieldAccess
55   * @since 2.0
56   */
57  public class FieldAccess extends Expression {
58      
59      /**
60       * The "expression" structural property of this node type.
61       * @since 3.0
62       */
63      public static final ChildPropertyDescriptor EXPRESSION_PROPERTY = 
64          new ChildPropertyDescriptor(FieldAccess.class, "expression", Expression.class, MANDATORY, CYCLE_RISK); //$NON-NLS-1$
65  
66      /**
67       * The "name" structural property of this node type.
68       * @since 3.0
69       */
70      public static final ChildPropertyDescriptor NAME_PROPERTY = 
71          new ChildPropertyDescriptor(FieldAccess.class, "name", SimpleName.class, MANDATORY, NO_CYCLE_RISK); //$NON-NLS-1$
72  
73      /**
74       * A list of property descriptors (element type: 
75       * {@link StructuralPropertyDescriptor}),
76       * or null if uninitialized.
77       */
78      private static final List   PROPERTY_DESCRIPTORS;
79      
80      static {
81          List   properyList = new ArrayList  (3);
82          createPropertyList(FieldAccess.class, properyList);
83          addProperty(EXPRESSION_PROPERTY, properyList);
84          addProperty(NAME_PROPERTY, properyList);
85          PROPERTY_DESCRIPTORS = reapPropertyList(properyList);
86      }
87  
88      /**
89       * Returns a list of structural property descriptors for this node type.
90       * Clients must not modify the result.
91       * 
92       * @param apiLevel the API level; one of the
93       * <code>AST.JLS*</code> constants
94  
95       * @return a list of property descriptors (element type: 
96       * {@link StructuralPropertyDescriptor})
97       * @since 3.0
98       */
99      public static List   propertyDescriptors(int apiLevel) {
100         return PROPERTY_DESCRIPTORS;
101     }
102             
103     /**
104      * The expression; lazily initialized; defaults to an unspecified,
105      * but legal, simple name.
106      */
107     private Expression expression = null;
108 
109     /**
110      * The field; lazily initialized; defaults to an unspecified,
111      * but legal, simple field name.
112      */
113     private SimpleName fieldName = null;
114 
115     /**
116      * Creates a new unparented node for a field access expression owned by the
117      * given AST. By default, the expression and field are both unspecified,
118      * but legal, names.
119      * <p>
120      * N.B. This constructor is package-private.
121      * </p>
122      * 
123      * @param ast the AST that is to own this node
124      */
125     FieldAccess(AST ast) {
126         super(ast);
127     }
128 
129     /* (omit javadoc for this method)
130      * Method declared on ASTNode.
131      */
132     final List   internalStructuralPropertiesForType(int apiLevel) {
133         return propertyDescriptors(apiLevel);
134     }
135     
136     /* (omit javadoc for this method)
137      * Method declared on ASTNode.
138      */
139     final ASTNode internalGetSetChildProperty(ChildPropertyDescriptor property, boolean get, ASTNode child) {
140         if (property == EXPRESSION_PROPERTY) {
141             if (get) {
142                 return getExpression();
143             } else {
144                 setExpression((Expression) child);
145                 return null;
146             }
147         }
148         if (property == NAME_PROPERTY) {
149             if (get) {
150                 return getName();
151             } else {
152                 setName((SimpleName) child);
153                 return null;
154             }
155         }
156         // allow default implementation to flag the error
157         return super.internalGetSetChildProperty(property, get, child);
158     }
159     
160     /* (omit javadoc for this method)
161      * Method declared on ASTNode.
162      */
163     final int getNodeType0() {
164         return FIELD_ACCESS;
165     }
166 
167     /* (omit javadoc for this method)
168      * Method declared on ASTNode.
169      */
170     ASTNode clone0(AST target) {
171         FieldAccess result = new FieldAccess(target);
172         result.setSourceRange(this.getStartPosition(), this.getLength());
173         result.setExpression((Expression) getExpression().clone(target));
174         result.setName((SimpleName) getName().clone(target));
175         return result;
176     }
177 
178     /* (omit javadoc for this method)
179      * Method declared on ASTNode.
180      */
181     final boolean subtreeMatch0(ASTMatcher matcher, Object   other) {
182         // dispatch to correct overloaded match method
183         return matcher.match(this, other);
184     }
185 
186     /* (omit javadoc for this method)
187      * Method declared on ASTNode.
188      */
189     void accept0(ASTVisitor visitor) {
190         boolean visitChildren = visitor.visit(this);
191         if (visitChildren) {
192             // visit children in normal left to right reading order
193             acceptChild(visitor, getExpression());
194             acceptChild(visitor, getName());
195         }
196         visitor.endVisit(this);
197     }
198     
199     /**
200      * Returns the expression of this field access expression.
201      * 
202      * @return the expression node
203      */ 
204     public Expression getExpression() {
205         if (this.expression == null) {
206             // lazy init must be thread-safe for readers
207             synchronized (this) {
208                 if (this.expression == null) {
209                     preLazyInit();
210                     this.expression = new SimpleName(this.ast);
211                     postLazyInit(this.expression, EXPRESSION_PROPERTY);
212                 }
213             }
214         }
215         return this.expression;
216     }
217         
218     /**
219      * Sets the expression of this field access expression.
220      * 
221      * @param expression the new expression
222      * @exception IllegalArgumentException if:
223      * <ul>
224      * <li>the node belongs to a different AST</li>
225      * <li>the node already has a parent</li>
226      * <li>a cycle in would be created</li>
227      * </ul>
228      */ 
229     public void setExpression(Expression expression) {
230         if (expression == null) {
231             throw new IllegalArgumentException  ();
232         }
233         ASTNode oldChild = this.expression;
234         preReplaceChild(oldChild, expression, EXPRESSION_PROPERTY);
235         this.expression = expression;
236         postReplaceChild(oldChild, expression, EXPRESSION_PROPERTY);
237     }
238 
239     /**
240      * Returns the name of the field accessed in this field access expression.
241      * 
242      * @return the field name
243      */ 
244     public SimpleName getName() {
245         if (this.fieldName == null) {
246             // lazy init must be thread-safe for readers
247             synchronized (this) {
248                 if (this.fieldName == null) {
249                     preLazyInit();
250                     this.fieldName = new SimpleName(this.ast);
251                     postLazyInit(this.fieldName, NAME_PROPERTY);
252                 }
253             }
254         }
255         return this.fieldName;
256     }
257         
258     /**
259      * Sets the name of the field accessed in this field access expression.
260      * 
261      * @param fieldName the field name
262      * @exception IllegalArgumentException if:
263      * <ul>
264      * <li>the node belongs to a different AST</li>
265      * <li>the node already has a parent</li>
266      * </ul>
267      */ 
268     public void setName(SimpleName fieldName) {
269         if (fieldName == null) {
270             throw new IllegalArgumentException  ();
271         }
272         ASTNode oldChild = this.fieldName;
273         preReplaceChild(oldChild, fieldName, NAME_PROPERTY);
274         this.fieldName = fieldName;
275         postReplaceChild(oldChild, fieldName, NAME_PROPERTY);
276     }
277 
278     /* (omit javadoc for this method)
279      * Method declared on ASTNode.
280      */
281     int memSize() {
282         // treat Code as free
283         return BASE_NODE_SIZE + 2 * 4;
284     }
285     
286     /**
287      * Resolves and returns the binding for the field accessed by this
288      * expression.
289      * <p>
290      * Note that bindings are generally unavailable unless requested when the
291      * AST is being built.
292      * </p>
293      *
294      * @return the variable binding, or <code>null</code> if the binding cannot
295      * be resolved
296      * @since 3.0
297      */
298     public IVariableBinding resolveFieldBinding() {
299         return this.ast.getBindingResolver().resolveField(this);
300     }
301     
302     /* (omit javadoc for this method)
303      * Method declared on ASTNode.
304      */
305     int treeSize() {
306         return 
307             memSize()
308             + (this.expression == null ? 0 : getExpression().treeSize())
309             + (this.fieldName == null ? 0 : getName().treeSize());
310     }
311 }
312 
313
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