/trunk/Examples/go/extend/runme.go

 1// This file illustrates the cross language polymorphism using directors.
 2
 3package main
 4
 5import (
 6	"fmt"
 7	. "./example"
 8)
 9
10type CEO struct{}
11
12func (p *CEO) GetPosition() string {
13	return "CEO"
14}
15
16func main() {
17	// Create an instance of CEO, a class derived from the Go
18	// proxy of the underlying C++ class.  The calls to getName()
19	// and getPosition() are standard, the call to getTitle() uses
20	// the director wrappers to call CEO.getPosition().
21
22	e := NewDirectorManager(new(CEO), "Alice")
23	fmt.Println(e.GetName(), " is a ", e.GetPosition())
24	fmt.Println("Just call her \"", e.GetTitle(), "\"")
25	fmt.Println("----------------------")
26
27	// Create a new EmployeeList instance.  This class does not
28	// have a C++ director wrapper, but can be used freely with
29	// other classes that do.
30
31	list := NewEmployeeList()
32
33	// EmployeeList owns its items, so we must surrender ownership
34	// of objects we add.
35	// e.DisownMemory()
36	list.AddEmployee(e)
37	fmt.Println("----------------------")
38
39	// Now we access the first four items in list (three are C++
40	// objects that EmployeeList's constructor adds, the last is
41	// our CEO).  The virtual methods of all these instances are
42	// treated the same.  For items 0, 1, and 2, all methods
43	// resolve in C++.  For item 3, our CEO, GetTitle calls
44	// GetPosition which resolves in Go.  The call to GetPosition
45	// is slightly different, however, because of the overidden
46	// GetPosition() call, since now the object reference has been
47	// "laundered" by passing through EmployeeList as an
48	// Employee*.  Previously, Go resolved the call immediately in
49	// CEO, but now Go thinks the object is an instance of class
50	// Employee.  So the call passes through the Employee proxy
51	// class and on to the C wrappers and C++ director, eventually
52	// ending up back at the Java CEO implementation of
53	// getPosition().  The call to GetTitle() for item 3 runs the
54	// C++ Employee::getTitle() method, which in turn calls
55	// GetPosition().  This virtual method call passes down
56	// through the C++ director class to the Java implementation
57	// in CEO.  All this routing takes place transparently.
58
59	fmt.Println("(position, title) for items 0-3:")
60
61	fmt.Println("  ", list.Get_item(0).GetPosition(), ", \"", list.Get_item(0).GetTitle(), "\"")
62	fmt.Println("  ", list.Get_item(1).GetPosition(), ", \"", list.Get_item(1).GetTitle(), "\"")
63	fmt.Println("  ", list.Get_item(2).GetPosition(), ", \"", list.Get_item(2).GetTitle(), "\"")
64	fmt.Println("  ", list.Get_item(3).GetPosition(), ", \"", list.Get_item(3).GetTitle(), "\"")
65	fmt.Println("----------------------")
66
67	// Time to delete the EmployeeList, which will delete all the
68	// Employee* items it contains. The last item is our CEO,
69	// which gets destroyed as well.
70	DeleteEmployeeList(list)
71	fmt.Println("----------------------")
72
73	// All done.
74
75	fmt.Println("Go exit")
76}