1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
// This file illustrates the cross language polymorphism using directors.
using System;
// CEO class, which overrides Employee::getPosition().
class CEO : Manager {
public CEO(String name) : base(name) {
}
public override String getPosition() {
return "CEO";
}
// Public method to stop the SWIG proxy base class from thinking it owns the underlying C++ memory.
public void disownMemory() {
swigCMemOwn = false;
}
}
public class runme
{
static void Main()
{
// Create an instance of CEO, a class derived from the C# proxy of the
// underlying C++ class. The calls to getName() and getPosition() are standard,
// the call to getTitle() uses the director wrappers to call CEO.getPosition().
CEO e = new CEO("Alice");
Console.WriteLine( e.getName() + " is a " + e.getPosition() );
Console.WriteLine( "Just call her \"" + e.getTitle() + "\"" );
Console.WriteLine( "----------------------" );
// Create a new EmployeeList instance. This class does not have a C++
// director wrapper, but can be used freely with other classes that do.
using (EmployeeList list = new EmployeeList()) {
// EmployeeList owns its items, so we must surrender ownership of objects we add.
e.disownMemory();
list.addEmployee(e);
Console.WriteLine( "----------------------" );
// 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, all methods resolve in C++. For item 3, our CEO, getTitle calls
// getPosition which resolves in C#. The call to getPosition is
// slightly different, however, because of the overridden getPosition() call, since
// now the object reference has been "laundered" by passing through
// EmployeeList as an Employee*. Previously, C# resolved the call
// immediately in CEO, but now C# thinks the object is an instance of
// class Employee. So the call passes through the
// Employee proxy class and on to the C wrappers and C++ director,
// eventually ending up back at the C# 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 C# implementation
// in CEO. All this routing takes place transparently.
Console.WriteLine( "(position, title) for items 0-3:" );
Console.WriteLine( " " + list.get_item(0).getPosition() + ", \"" + list.get_item(0).getTitle() + "\"" );
Console.WriteLine( " " + list.get_item(1).getPosition() + ", \"" + list.get_item(1).getTitle() + "\"" );
Console.WriteLine( " " + list.get_item(2).getPosition() + ", \"" + list.get_item(2).getTitle() + "\"" );
Console.WriteLine( " " + list.get_item(3).getPosition() + ", \"" + list.get_item(3).getTitle() + "\"" );
Console.WriteLine( "----------------------" );
// The using statement ensures the EmployeeList.Dispose() will be called, which will delete all the Employee*
// items it contains. The last item is our CEO, which gets destroyed as well.
}
Console.WriteLine( "----------------------" );
// All done.
Console.WriteLine( "C# exit" );
}
}
|
