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/// This file illustrates the cross language polymorphism using directors.
module runme;
import std.stdio;
import example;
// CEO class, which overrides Employee.getPosition().
class CEO : Manager {
public:
this( string name ) {
super( name );
}
override string getPosition() const {
return "CEO";
}
// Public method to stop the SWIG proxy base class from thinking it owns the underlying C++ memory.
void disownMemory() {
swigCMemOwn = false;
}
}
void main() {
// Create an instance of CEO, a class derived from the D 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().
auto e = new CEO( "Alice" );
writefln( "%s is a %s.", e.getName(), e.getPosition() );
writefln( "Just call her '%s'.", e.getTitle() );
writeln( "----------------------" );
{
// Create a new EmployeeList instance. This class does not have a C++
// director wrapper, but can be used freely with other classes that do.
scope auto list = new EmployeeList();
// EmployeeList owns its items, so we must surrender ownership of objects we add.
e.disownMemory();
list.addEmployee(e);
writeln( "----------------------" );
// 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 D. 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, D resolved the call
// immediately in CEO, but now D 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 D 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 D implementation
// in CEO. All this routing takes place transparently.
writeln( "(position, title) for items 0-3:" );
writefln( " %s, '%s'", list.getItem(0).getPosition(), list.getItem(0).getTitle() );
writefln( " %s, '%s'", list.getItem(1).getPosition(), list.getItem(1).getTitle() );
writefln( " %s, '%s'", list.getItem(2).getPosition(), list.getItem(2).getTitle() );
writefln( " %s, '%s'", list.getItem(3).getPosition(), list.getItem(3).getTitle() );
writeln( "----------------------" );
// All Employees will be destroyed when the EmployeeList goes out of scope,
// including the CEO instance.
}
writeln( "----------------------" );
// All done.
writeln( "Exiting cleanly from D code." );
}
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