mirror of https://github.com/swig/swig
76 lines
3.0 KiB
D
76 lines
3.0 KiB
D
/// This file illustrates the cross language polymorphism using directors.
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module runme;
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import std.stdio;
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import example;
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// CEO class, which overrides Employee.getPosition().
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class CEO : Manager {
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public:
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this( string name ) {
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super( name );
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}
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override string getPosition() const {
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return "CEO";
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}
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// Public method to stop the SWIG proxy base class from thinking it owns the underlying C++ memory.
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void disownMemory() {
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swigCMemOwn = false;
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}
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}
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void main() {
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// Create an instance of CEO, a class derived from the D proxy of the
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// underlying C++ class. The calls to getName() and getPosition() are standard,
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// the call to getTitle() uses the director wrappers to call CEO.getPosition().
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auto e = new CEO( "Alice" );
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writefln( "%s is a %s.", e.getName(), e.getPosition() );
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writefln( "Just call her '%s'.", e.getTitle() );
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writeln( "----------------------" );
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{
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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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scope auto list = new EmployeeList();
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// EmployeeList owns its items, so we must surrender ownership of objects we add.
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e.disownMemory();
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list.addEmployee(e);
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writeln( "----------------------" );
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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, all methods resolve in C++. For item 3, our CEO, getTitle calls
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// getPosition which resolves in D. The call to getPosition is
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// slightly different, however, because of the overridden getPosition() call, since
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// now the object reference has been "laundered" by passing through
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// EmployeeList as an Employee*. Previously, D resolved the call
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// immediately in CEO, but now D thinks the object is an instance of
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// class Employee. 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 D 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 D implementation
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// in CEO. All this routing takes place transparently.
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writeln( "(position, title) for items 0-3:" );
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writefln( " %s, '%s'", list.getItem(0).getPosition(), list.getItem(0).getTitle() );
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writefln( " %s, '%s'", list.getItem(1).getPosition(), list.getItem(1).getTitle() );
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writefln( " %s, '%s'", list.getItem(2).getPosition(), list.getItem(2).getTitle() );
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writefln( " %s, '%s'", list.getItem(3).getPosition(), list.getItem(3).getTitle() );
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writeln( "----------------------" );
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// All Employees will be destroyed when the EmployeeList goes out of scope,
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// including the CEO instance.
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}
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writeln( "----------------------" );
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// All done.
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writeln( "Exiting cleanly from D code." );
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}
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