Cross-language polymorphism

This example demonstrates cross language polymorphism using SWIG directors.

This allows you to define a base class in C++ which contains some virtual methods. Then you can derive from that class in Python. Then you instantiate a C++ object from Python where this C++ object takes a pointer to the base class type. Then you can call a virtual method from C++.

If a base class type was used, then it calls the C++ virtual method. But if a Python derived class is used, it calls the Python virtual method from C++! If this doesn't blow your mind at least a little bit, then I don't think you understand what is going on, go through the example more slowly until your mind is blown ;-)

Building

Build the SWIG wrapper using the following shell script:

./build_swig.sh

Evaluating

The runme.py example constructs the class first using a base class type as implemented in C++, then using a derived class type as implemented in Python.

./runme.py

Code Files

• C++ implementation
  • example.h/.cpp
• SWIG
  • Interface File
    • example.i
  • Distutils script
    • setup.py
• Test code to run it all
  • runme.py

Exercise

Fill in the TODO: blocks present in runme.py.