add 'attribute' macros for python

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@5777 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Lib/python/attribute.i

@@ -0,0 +1,121 @@
+%{
+#include <iostream>
+%}
+
+/*
+  Attribute implementation using JOHN E LENZ ideas.
+
+  The following macros convert a pair of set/get methods
+  into a "native" python attribute.
+
+  Use %attribute when you have a pair of get/set methods
+  like in:
+
+  %attribute(A, int, a, get_a, set_a);
+
+  struct A
+  {    
+    int get_a() const 
+    {
+      return _a;
+    }
+    
+    void set_a(int aa) 
+    {
+      _a = aa;
+    }
+  };
+
+  If you don't provide a 'set' method, a 'read-only' attribute
+  is generated, ie, like in:
+
+  %attribute(A, int, c, get_c);
+
+
+  Use %attribute_ref when you have const/non-const reference
+  access methods, like in:
+
+  %attribute_ref(A, int, b);
+
+  struct A
+  {    
+    const int& b() const 
+    {
+      return _b;
+    }
+    
+    int& b() 
+    {
+      return _b;
+    }
+  };
+
+  You can also use
+
+  %attribute_ref(class, type, pyattr, cppame);
+  
+  if the internal C++ reference methods have a different
+  name from the python attribute you want.
+  
+  Then you can use the instances like:
+
+  x = A() 
+  x.a = 3        # calls A::set_a
+  print x.a      # calls A::get_a 
+
+  x.b = 3        # calls A::b() 
+  print x.b      # calls A::b() const
+  
+*/
+
+
+%define %_attribute(Class, type, attr, get, set) 
+%extend Class {
+  type attr;
+}
+%{
+  template <class C>
+  inline type Class ##_## attr ## _get(C *t) {
+    return get;
+  }
+  template <class C>
+  inline type Class ##_## attr ## _set(C *t, const type& val) {
+    set;
+  }
+%}
+%enddef
+
+%define %attribute(Class, type, attr, get, ...) 
+#if #__VA_ARGS__ != ""
+  %_attribute(Class, type, attr, t->get(), t->__VA_ARGS__(val)) 
+#else
+  %_attribute(Class, type, attr, t->get(), 
+	      std::cerr << "'attr' is a read-only attribute" << std::endl);
+#endif
+%enddef
+
+%define %_attribute_ref(Class, type, attr, ref_name) 
+%extend Class {
+  type attr;
+}
+%ignore Class::ref_name();
+%ignore Class::ref_name() const;
+%{
+  template <class C>
+  inline type Class ##_## attr ## _get(C *t) {
+    return t->ref_name();
+  }
+  template <class C>
+  inline type Class ##_## attr ## _set(C *t, const type& val) {
+     t->ref_name() = val;
+  }
+%}
+%enddef
+
+%define %attribute_ref(Class, type, attr, ...) 
+#if #__VA_ARGS__ == ""
+%_attribute_ref(Class, type, attr, attr) 
+#else
+%_attribute_ref(Class, type, attr, __VA_ARGS__)
+#endif
+%enddef