mirror of https://github.com/swig/swig
83 lines
3.2 KiB
Python
83 lines
3.2 KiB
Python
# file: runme.py
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# This file illustrates the cross language polymorphism using directors.
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import example
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# CEO class, which overrides Employee::getPosition().
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class CEO(example.Manager):
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def __init__(self, name):
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example.Manager.__init__(self, name)
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def getPosition(self):
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return "CEO"
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# Create an instance of our employee extension class, CEO. The calls to
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# getName() and getPosition() are standard, the call to getTitle() uses
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# the director wrappers to call CEO.getPosition.
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e = CEO("Alice")
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print("%s is a %s" % (e.getName(), e.getPosition()))
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print("Just call her \"%s\"" % e.getTitle())
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print("----------------------")
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# Create a new EmployeeList instance. This class does not have a C++
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# director wrapper, but can be used freely with other classes that do.
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list = example.EmployeeList()
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# EmployeeList owns its items, so we must surrender ownership of objects
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# we add. This involves first calling the __disown__ method to tell the
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# C++ director to start reference counting. We reassign the resulting
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# weakref.proxy to e so that no hard references remain. This can also be
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# done when the object is constructed, as in: e =
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# CEO("Alice").__disown__()
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e = e.__disown__()
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list.addEmployee(e)
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print("----------------------")
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# Now we access the first four items in list (three are C++ objects that
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# EmployeeList's constructor adds, the last is our CEO). The virtual
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# methods of all these instances are treated the same. For items 0, 1, and
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# 2, both all methods resolve in C++. For item 3, our CEO, getTitle calls
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# getPosition which resolves in Python. The call to getPosition is
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# slightly different, however, from the e.getPosition() call above, since
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# now the object reference has been "laundered" by passing through
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# EmployeeList as an Employee*. Previously, Python resolved the call
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# immediately in CEO, but now Python thinks the object is an instance of
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# class Employee (actually EmployeePtr). So the call passes through the
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# Employee proxy class and on to the C wrappers and C++ director,
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# eventually ending up back at the CEO implementation of getPosition().
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# The call to getTitle() for item 3 runs the C++ Employee::getTitle()
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# method, which in turn calls getPosition(). This virtual method call
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# passes down through the C++ director class to the Python implementation
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# in CEO. All this routing takes place transparently.
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print("(position, title) for items 0-3:")
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print(" %s, \"%s\"" % (list.get_item(0).getPosition(), list.get_item(0).getTitle()))
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print(" %s, \"%s\"" % (list.get_item(1).getPosition(), list.get_item(1).getTitle()))
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print(" %s, \"%s\"" % (list.get_item(2).getPosition(), list.get_item(2).getTitle()))
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print(" %s, \"%s\"" % (list.get_item(3).getPosition(), list.get_item(3).getTitle()))
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print("----------------------")
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# Time to delete the EmployeeList, which will delete all the Employee*
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# items it contains. The last item is our CEO, which gets destroyed as its
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# reference count goes to zero. The Python destructor runs, and is still
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# able to call self.getName() since the underlying C++ object still
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# exists. After this destructor runs the remaining C++ destructors run as
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# usual to destroy the object.
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del list
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print("----------------------")
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# All done.
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print("python exit")
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