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Java > Open Source Codes > bsh > BlockNameSpace


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33
34 package bsh;
35
36 /**
37     A specialized namespace for Blocks (e.g. the body of a "for" statement).
38     The Block acts like a child namespace but only for typed variables
39     declared within it (block local scope) or untyped variables explicitly set
40     in it via setBlockVariable(). Otherwise variable assignment
41     (including untyped variable usage) acts like it is part of the containing
42     block.
43     <p>
44 */
45 /*
46     Note: This class essentially just delegates most of its methods to its
47     parent. The setVariable() indirection is very small. We could probably
48     fold this functionality back into the base NameSpace as a special case.
49     But this has changed a few times so I'd like to leave this abstraction for
50     now.
51 */
52 class BlockNameSpace extends NameSpace
53 {
54     public BlockNameSpace( NameSpace parent )
55         throws EvalError
56     {
57         super( parent, parent.getName()+ "/BlockNameSpace" );
58     }
59
60     /**
61         Override the standard namespace behavior to make assignments
62         happen in our parent (enclosing) namespace, unless the variable has
63         already been assigned here via a typed declaration or through
64         the special setBlockVariable() (used for untyped args in try/catch).
65         <p>
66         i.e. only allow typed var declaration to happen in this namespace.
67         Typed vars are handled in the ordinary way local scope. All untyped
68         assignments are delegated to the enclosing context.
69     */
70     /*
71         Note: it may see like with the new 1.3 scoping this test could be
72         removed, but it cannot. When recurse is false we still need to set the
73         variable in our parent, not here.
74     */
75     public void setVariable(
76         String JavaDoc name, Object JavaDoc value, boolean strictJava, boolean recurse )
77         throws UtilEvalError
78     {
79         if ( weHaveVar( name ) )
80             // set the var here in the block namespace
81 super.setVariable( name, value, strictJava, false );
82         else
83             // set the var in the enclosing (parent) namespace
84 getParent().setVariable( name, value, strictJava, recurse );
85     }
86
87     /**
88         Set an untyped variable in the block namespace.
89         The BlockNameSpace would normally delegate this set to the parent.
90         Typed variables are naturally set locally.
91         This is used in try/catch block argument.
92     */
93     public void setBlockVariable( String JavaDoc name, Object JavaDoc value )
94         throws UtilEvalError
95     {
96         super.setVariable( name, value, false/*strict?*/, false );
97     }
98
99     /**
100         We have the variable: either it was declared here with a type, giving
101         it block local scope or an untyped var was explicitly set here via
102         setBlockVariable().
103     */
104     private boolean weHaveVar( String JavaDoc name )
105     {
106         // super.variables.containsKey( name ) not any faster, I checked
107 try {
108             return super.getVariableImpl( name, false ) != null;
109         } catch ( UtilEvalError e ) { return false; }
110     }
111
112 /**
113         Get the actual BlockNameSpace 'this' reference.
114         <p/>
115         Normally a 'this' reference to a BlockNameSpace (e.g. if () { } )
116         resolves to the parent namespace (e.g. the namespace containing the
117         "if" statement). However when code inside the BlockNameSpace needs to
118         resolve things relative to 'this' we must use the actual block's 'this'
119         reference. Name.java is smart enough to handle this using
120         getBlockThis().
121         @see #getThis( Interpreter )
122     This getBlockThis( Interpreter declaringInterpreter )
123     {
124         return super.getThis( declaringInterpreter );
125     }
126 */
127
128     //
129 // Begin methods which simply delegate to our parent (enclosing scope)
130 //
131
132     /**
133         This method recurses to find the nearest non-BlockNameSpace parent.
134
135     public NameSpace getParent()
136     {
137         NameSpace parent = super.getParent();
138         if ( parent instanceof BlockNameSpace )
139             return parent.getParent();
140         else
141             return parent;
142     }
143 */
144     /** do we need this? */
145     private NameSpace getNonBlockParent()
146     {
147         NameSpace parent = super.getParent();
148         if ( parent instanceof BlockNameSpace )
149             return ((BlockNameSpace)parent).getNonBlockParent();
150         else
151             return parent;
152     }
153
154     /**
155         Get a 'this' reference is our parent's 'this' for the object closure.
156         e.g. Normally a 'this' reference to a BlockNameSpace (e.g. if () { } )
157         resolves to the parent namespace (e.g. the namespace containing the
158         "if" statement).
159         @see #getBlockThis( Interpreter )
160     */
161     This getThis( Interpreter declaringInterpreter ) {
162         return getNonBlockParent().getThis( declaringInterpreter );
163     }
164
165     /**
166         super is our parent's super
167     */
168     public This getSuper( Interpreter declaringInterpreter ) {
169         return getNonBlockParent().getSuper( declaringInterpreter );
170     }
171
172     /**
173         delegate import to our parent
174     */
175     public void importClass(String JavaDoc name) {
176         getParent().importClass( name );
177     }
178
179     /**
180         delegate import to our parent
181     */
182     public void importPackage(String JavaDoc name) {
183         getParent().importPackage( name );
184     }
185
186     public void setMethod(String JavaDoc name, BshMethod method)
187         throws UtilEvalError
188     {
189         getParent().setMethod( name, method );
190     }
191 }
192
193
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