I was asking on the Mac Pascal list if Delphi had any ways to invoke methods on
objects which the class was unknown at compile time (like a class that invokes
a user defined delegate commonly used in Cocoa Mac programming and I assume
Delphi not knowing) and one user told me interfaces will work for this. Btw,
I'm aware you can use strings to invoke methods with a single argument but I
wanted something better since this has been a real drawback in Pascal for me in
recent years.
The idea is Main.pas has a delegate class which implements IMyInterface and
MyInterface.pas declares the interface and can invoke its methods using a
generic delegate object (typed TObject). This is really typical of UI elements
like a button that wants to tell a receiver an action occurred but doesn't know
the class of the receiving object. Providing this example works it's sort of a
workaround to multiple inheritence but I don't see that Pascal would be capable
of this, i.e. simply type casting an object and forcing it to call a method
that may or may not exist (I feel like I tried this before and got crashing).
He swears this works and no one else answered otherwise but I'm getting "Error:
Class or Object types "TObject" and "IMyInterface" are not related" errors at
the line shown below.
Any ideas? Thanks.
====================
{$mode delphi}
{$interfaces corba}
unit MyInterface;
interface
type
IMyInterface = interface
procedure DoThis (value: integer);
end;
procedure InvokeDelegate (delegate: TObject);
implementation
procedure InvokeDelegate (delegate: TObject);
var
intfDelegate: IMyInterface;
begin
ERROR ====> intfDelegate := IMyInterface(delegate);
intfDelegate.DoThis(1);
end;
end.
====================
{$mode delphi}
{$interfaces corba}
program Main;
uses
MyInterface;
type
TMyDelegate = class (TInterfacedObject, IMyDelegate)
procedure DoThis (value: integer);
end;
procedure TMyDelegate.DoThis (value: integer);
begin
writeln('did this ', value);
end;
var
delegate: TMyDelegate;
begin
delegate := TMyDelegate.Create;
TestDelegate(delegate);
end.
Regards,
Ryan Joseph
thealchemistguild.com
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