two director examples for python

git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk/SWIG@4447 626c5289-ae23-0410-ae9c-e8d60b6d4f22

Examples/python/extend/runme.py

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+# file: runme.py
+
+# This file illustrates the cross language polymorphism using directors.
+
+import example 
+
+
+# CEO class, which overrides Employee::getPosition().
+
+class CEO(example.Manager):
+	def __init__(self, name):
+		example.Manager.__init__(self, name)
+	def getPosition(self):
+		return "CEO"
+	def __del__(self):
+		print "CEO.__del__(),", self.getName()
+		# for shadow class extensions that are not "disowned" and
+		# define a __del__ method, it is very important to call the 
+		# base class __del__.  otherwise the c++ objects will never
+		# be deleted.
+		example.Manager.__del__(self)
+
+
+# Create an instance of our employee extension class, CEO. The calls to
+# getName() and getPosition() are standard, the call to getTitle() uses
+# the director wrappers to call CEO.getPosition. e = CEO("Alice")
+
+e = CEO("Alice")
+print e.getName(), "is a", e.getPosition()
+print "Just call her \"%s\"" % e.getTitle()
+print "----------------------"
+
+
+# Create a new EmployeeList instance.  This class does not have a C++
+# director wrapper, but can be used freely with other classes that do.
+
+list = example.EmployeeList()
+
+# EmployeeList owns its items, so we must surrender ownership of objects
+# we add. This involves first calling the __disown__ method to tell the
+# C++ director to start reference counting. We reassign the resulting
+# weakref.proxy to e so that no hard references remain. This can also be
+# done when the object is constructed, as in: e =
+# CEO("Alice").__disown__()
+
+e = e.__disown__()
+list.addEmployee(e)
+print "----------------------"
+
+# Now we access the first four items in list (three are C++ objects that
+# EmployeeList's constructor adds, the last is our CEO). The virtual
+# methods of all these instances are treated the same. For items 0, 1, and
+# 2, both all methods resolve in C++. For item 3, our CEO, getTitle calls
+# getPosition which resolves in Python. The call to getPosition is
+# slightly different, however, from the e.getPosition() call above, since
+# now the object reference has been "laundered" by passing through
+# EmployeeList as an Employee*. Previously, Python resolved the call
+# immediately in CEO, but now Python thinks the object is an instance of
+# class Employee (actually EmployeePtr). So the call passes through the
+# Employee shadow class and on to the C wrappers and C++ director,
+# eventually ending up back at the CEO implementation of getPosition().
+# The call to getTitle() for item 3 runs the C++ Employee::getTitle()
+# method, which in turn calls getPosition(). This virtual method call
+# passes down through the C++ director class to the Python implementation
+# in CEO. All this routing takes place transparently.
+
+print "(position, title) for items 0-3:"
+
+print "  %s, \"%s\"" % (list.get_item(0).getPosition(), list.get_item(0).getTitle())
+print "  %s, \"%s\"" % (list.get_item(1).getPosition(), list.get_item(1).getTitle())
+print "  %s, \"%s\"" % (list.get_item(2).getPosition(), list.get_item(2).getTitle())
+print "  %s, \"%s\"" % (list.get_item(3).getPosition(), list.get_item(3).getTitle())
+print "----------------------"
+
+# Time to delete the EmployeeList, which will delete all the Employee*
+# items it contains. The last item is our CEO, which gets destroyed as its
+# reference count goes to zero. The Python destructor runs, and is still
+# able to call self.getName() since the underlying C++ object still
+# exists. After this destructor runs the remaining C++ destructors run as
+# usual to destroy the object.
+
+del list
+print "----------------------"
+
+# All done.
+
+print "python exit"
+