34c97ffdbd
Fix numerous inaccuracies in index.html (where it exists) and eliminate unnecessary differences between the example code being wrapped.
156 lines
2.9 KiB
HTML
156 lines
2.9 KiB
HTML
<html>
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<head>
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<title>SWIG:Examples:ruby:class</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/ruby/class/</tt>
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<hr>
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<H2>Wrapping a simple C++ class</H2>
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<p>
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This example illustrates wrapping a simple C++ class to give a Python class.
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<h2>The C++ Code</h2>
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Suppose you have some C++ classes described by the following (and admittedly lame)
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header file:
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<blockquote>
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<pre>
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/* File : example.h */
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class Shape {
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public:
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Shape() {
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nshapes++;
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}
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virtual ~Shape() {
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nshapes--;
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}
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double x, y;
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void move(double dx, double dy);
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virtual double area() = 0;
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virtual double perimeter() = 0;
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static int nshapes;
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};
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class Circle : public Shape {
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private:
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double radius;
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public:
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Circle(double r) : radius(r) { }
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virtual double area();
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virtual double perimeter();
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};
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class Square : public Shape {
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private:
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double width;
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public:
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Square(double w) : width(w) { }
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virtual double area();
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virtual double perimeter();
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};
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</pre>
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</blockquote>
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<h2>The SWIG interface</h2>
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A simple SWIG interface for this can be built by simply grabbing the header file
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like this:
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<blockquote>
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<pre>
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/* File : example.i */
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%module example
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%{
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#include "example.h"
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%}
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/* Let's just grab the original header file here */
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%include "example.h"
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</pre>
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</blockquote>
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Note: when creating a C++ extension, you must run SWIG with the <tt>-c++</tt> option like this:
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<blockquote>
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<pre>
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% swig -c++ -ruby example.i
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</pre>
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</blockquote>
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<h2>A sample Ruby script</h2>
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Click <a href="runme.rb">here</a> to see a script that calls the C++ functions from Ruby.
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<h2>Key points</h2>
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<ul>
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<li>To create a new object, you call a constructor like this:
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<blockquote>
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<pre>
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c = Example::Circle.new(10)
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</pre>
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</blockquote>
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<p>
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<li>To access member data, a pair of accessor methods are used.
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For example:
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<blockquote>
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<pre>
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c.x = 15 # Set member data
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x = c.x # Get member data
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</pre>
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</blockquote>
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<p>
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<li>To invoke a member function, you simply do this
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<blockquote>
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<pre>
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print "The area is ", c.area, "\n"
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</pre>
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</blockquote>
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<p>
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<li>When a instance of Ruby level wrapper class is garbage collected by the
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Ruby interpreter, the corresponding C++ destructor is automatically invoked.
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<p>
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<li>Static member variables are wrapped as Ruby class accessor methods.
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For example:
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<blockquote>
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<pre>
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n = Shape.nshapes # Get a static data member
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Shapes.nshapes = 13 # Set a static data member
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</pre>
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</blockquote>
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</ul>
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<h2>General Comments</h2>
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<ul>
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<li>Ruby module of SWIG differs from other language modules in wrapping C++
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interfaces. They provide lower-level interfaces and optional higher-level
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interfaces know as proxy classes. Ruby module needs no such redundancy
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due to Ruby's sophisticated extension API.
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<li>SWIG <b>does</b> know how to properly perform upcasting of objects in
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an inheritance hierarchy except for multiple inheritance.
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<li>C++ Namespaces - %nspace isn't yet supported for Python.
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</ul>
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<hr>
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</body>
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</html>
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