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<html>
<head>
<title>SWIG:Examples:perl5:class</title>
</head>
<body bgcolor="#ffffff">
<tt>SWIG/Examples/perl5/class/</tt>
<hr>
<H2>Wrapping a simple C++ class</H2>
<p>
This example illustrates the most primitive form of C++ class wrapping performed
by SWIG. In this case, C++ classes are simply transformed into a collection of
C-style functions that provide access to 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++ -perl example.i
</pre>
</blockquote>
<h2>A sample Perl script</h2>
Click <a href="runme.pl">here</a> to see a script that calls the C++ functions from Perl.
<h2>Key points</h2>
<ul>
<li>To create a new object, you call a constructor like this:
<blockquote>
<pre>
$c = new example::Circle(10.0);
</pre>
</blockquote>
<p>
<li>You can access member data like so:
<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();
</pre>
</blockquote>
<p>
<li>To invoke a destructor, simply do this:
<blockquote>
<pre>
$c->DESTROY(); # Deletes a shape
</pre>
</blockquote>
<p>
<li>Static member variables are wrapped like so:
<blockquote>
<pre>
$n = $example::Shape::nshapes; # Get a static data member
$example::Shapes::nshapes = 13; # Set a static data member
</pre>
</blockquote>
</ul>
<h2>General Comments</h2>
<ul>
<li>SWIG <b>does</b> know how to properly perform upcasting of objects in an inheritance
hierarchy (including multiple inheritance). Therefore it is perfectly safe to pass
an object of a derived class to any function involving a base class.
<li>C++ Namespaces - %nspace isn't yet supported for Perl.
</ul>
<hr>
</body>
</html>
|
