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Examples/python/class/index.html
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sunoru
Fix some typos in docs and examples and make the code look nicer.
31 дек 2016, 18:06
31 дек 2016, 18:06
8985c34
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<html> <head> <title>SWIG:Examples:python:class</title> </head> <body bgcolor="#ffffff"> <tt>SWIG/Examples/python/class/</tt> <hr> <H2>Wrapping a simple C++ class</H2> <p> This example illustrates wrapping a simple C++ class to give a Python class. <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++ -python example.i </pre> </blockquote> <h2>A sample Python script</h2> Click <a href="runme.py">here</a> to see a script that calls the C++ functions from Python. <h2>Key points</h2> <ul> <li>To create a new object, you call a constructor like this: <blockquote> <pre> c = example.new_Circle(10.0) </pre> </blockquote> <p> <li>Member variables of the C++ class are wrapped as attributes of the Python class. For example: <blockquote> <pre> c.x = 15 # Set member data x = c.x # Get member data </pre> </blockquote> <p> <li>Member function are invoked as you would expect: <blockquote> <pre> print "The area is ", c.area() </pre> </blockquote> <p> <li>To invoke a destructor, simply call <code>del</code> on the object: <blockquote> <pre> del c # Deletes a shape </pre> </blockquote> <p> <li>Static member variables are wrapped as C global variables. For example: <blockquote> <pre> n = example.cvar.Shape_nshapes # Get a static data member example.cvar.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 Python. </ul> <hr> </body> </html>