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+<html>
+<head>
+<title>SWIG:Examples:ruby:class</title>
+</head>
+
+<body bgcolor="#ffffff">
+
+
+<tt>SWIG/Examples/ruby/class/</tt>
+<hr>
+
+<H2>Wrapping a simple C++ class</H2>
+
+<p>
+This example illustrates C++ class wrapping performed by SWIG.
+C++ classes are simply transformed into Ruby classes that provide methods to
+access class members.
+
+<h2>The C++ Code</h2>
+
+Suppose you have some C++ classes described by the following (and admittedly lame) 
+header file:
+
+<blockquote>
+<pre>
+/* File : example.h */
+
+class Shape {
+public:
+  Shape() {
+    nshapes++;
+  }
+  virtual ~Shape() {
+    nshapes--;
+  };
+  double  x, y;   
+  void    move(double dx, double dy);
+  virtual double area() = 0;
+  virtual double perimeter() = 0;
+  static  int nshapes;
+};
+
+class Circle : public Shape {
+private:
+  double radius;
+public:
+  Circle(double r) : radius(r) { };
+  virtual double area();
+  virtual double perimeter();
+};
+
+class Square : public Shape {
+private:
+  double width;
+public:
+  Square(double w) : width(w) { };
+  virtual double area();
+  virtual double perimeter();
+};
+</pre>
+</blockquote>
+
+<h2>The SWIG interface</h2>
+
+A simple SWIG interface for this can be built by simply grabbing the header file
+like this:
+
+<blockquote>
+<pre>
+/* File : example.i */
+%module example
+
+%{
+#include "example.h"
+%}
+
+/* Let's just grab the original header file here */
+%include "example.h"
+</pre>
+</blockquote>
+
+Note: when creating a C++ extension, you must run SWIG with the <tt>-c++</tt> option like this:
+<blockquote>
+<pre>
+% swig -c++ -ruby example.i
+</pre>
+</blockquote>
+
+<h2>A sample Ruby script</h2>
+
+Click <a href="runme.rb">here</a> to see a script that calls the C++ functions from Ruby.
+
+<h2>Key points</h2>
+
+<ul>
+<li>To create a new object, you call a constructor like this:
+
+<blockquote>
+<pre>
+c = Example::Circle.new(10)
+</pre>
+</blockquote>
+
+<p>
+<li>To access member data, a pair of accessor methods are used.
+For example:
+
+<blockquote>
+<pre>
+c.x = 15    # Set member data
+x = c.x     # Get member data
+</pre>
+</blockquote>
+
+<p>
+<li>To invoke a member function, you simply do this
+
+<blockquote>
+<pre>
+print "The area is ", c.area, "\n"
+</pre>
+</blockquote>
+
+<p>
+<li>When a instance of Ruby level wrapper class is garbage collected by
+Ruby interpreter, the corresponding C++ destructor is automatically invoked.
+(Note: destructors are currently not inherited. This might change later.
+Until then, use <tt>-make_default</tt>).
+
+<p>
+<li>Static member variables are wrapped as Ruby class accessor methods.
+For example:
+
+<blockquote>
+<pre>
+n = Shape.nshapes     # Get a static data member
+Shapes.nshapes = 13   # Set a static data member
+</pre>
+</blockquote>
+
+</ul>
+
+<h2>General Comments</h2>
+
+<ul>
+<li>Ruby module of SWIG differs from other language modules in wrapping C++
+interfaces.  They provides lower-level interfaces and optional higher-level
+interfaces know as proxy classes.  Ruby module needs no such redundancy
+due to Ruby's sophisticated extension API.
+
+<p>
+<li>SWIG *does* know how to properly perform upcasting of objects in
+an inheritance hierarchy except for multiple inheritance.
+
+<p>
+<li>A wide variety of C++ features are not currently supported by SWIG.  Here is the
+short and incomplete list:
+
+<p>
+<ul>
+<li>Overloaded methods and functions.  SWIG wrappers don't know how to resolve name
+conflicts so you must give an alternative name to any overloaded method name using the
+%name directive like this:
+
+<blockquote>
+<pre>
+void foo(int a);  
+%name(foo2) void foo(double a, double b);
+</pre>
+</blockquote>
+
+<p>
+<li>Overloaded operators.  Not supported at all. The only workaround for this is
+to write a helper function. For example:
+
+<blockquote>
+<pre>
+%inline %{
+    Vector *vector_add(Vector *a, Vector *b) {
+          ... whatever ...
+    }
+%}
+</pre>
+</blockquote>
+
+<p>
+<li>Namespaces.  Not supported at all. Won't be supported until SWIG2.0 (if at all).
+
+</ul>
+<p>
+
+<li>Dave's snide remark: Like a large bottle of strong Tequilla, it's better to
+use C++	in moderation.
+
+</ul>
+
+<hr>
+</body>
+</html>