Invoke methods in Pascal - pascal

Question

I am in front of following problem:
My Main programming Language is C++ with the Qt4 Library, but now I have to write a Pascal Wrapper, which should give the possibility to use the functions of a C DLL in Pascal.
Now I want to make it possible to invoke a method from any Pointer. But I can't find a Pascal method to invoke a method. I want something like the QMetaObject::invokeMethod method in QT. I got following code:
unit CgPConnect;
//{$mode objfpc}{$H+}
{$mode delphi}
interface
uses
Classes, SysUtils, dynlibs;
type
Callback = Record
var callbackObject: Pointer;
var objectFunction: string;
end;
CallbackObject = Record
var objectName: string;
var callback: Callback;
end;
MutableObject = Object
var name: string;
var state: string;
var properties: array of VariantMap;
var annotations: array of VariantMap;
end;
PConnect = Class
constructor create(connectorPath: string);
destructor destroy;
private
var hostactionCallbacks: array of CallbackObject;
var mConnectorPath: string;
var mConnectorLibrary: TLibHandle;
function loadConnectorLibrary: Boolean;
public
procedure registerCallbackForHostaction(objectName, objectFunction: string; callbackObject: pointer);
procedure callHostactionCallback(receivedObject :MutableObject);
var mLibraryLoaded: Boolean;
end;
implementation
constructor PConnect.create(connectorPath: string);
begin
mConnectorPath:= connectorPath;
mLibraryLoaded:= false;
//Eventuell noch slash hinzufügen
mLibraryLoaded:= loadConnectorLibrary;
end;
destructor PConnect.destroy;
begin
UnloadLibrary(mConnectorLibrary);
end;
procedure PConnect.registerCallbackForHostaction(objectName, objectFunction: string; callbackObject: pointer);
var c: Callback;
var callbackCount: integer;
begin
if mLibraryLoaded = true then
begin
c.callbackObject:= callbackObject;
c.objectFunction:= objectFunction;
callbackCount:= Length(hostactionCallbacks)+1;
SetLength(hostactionCallbacks, callbackCount);
hostactionCallbacks[callbackCount].objectName:= objectName;
hostactionCallbacks[callbackCount].callback:= c;
end;
end;
procedure PConnect.callHostactionCallback(receivedObject :MutableObject);
var receivedObjectName, objectFunction: string;
var i, count: integer;
var callbackObject: pointer;
begin
if mLibraryLoaded = true then
begin
receivedObjectName:= receivedObject.name;
count:= Length(hostactionCallbacks);
for i:=0 to count do
begin
if hostactionCallbacks[i].objectName = receivedObjectName
begin
objectFunction:= hostactionCallbacks[i].callback.objectFunction;
callbackObject:= hostactionCallbacks[i].callback.callbackObject;
if callbackObject <> 0 then
//INVOKE METHOD (objectFunction) OF OBJECT (callbackObject)
end;
end;
end;
end;
end.
I would be happy about a fast answer :)

Answer 1

You cannot directly and portably call a C++ method from Pascal. If your callbackfunction is a C++ object, forget it.
Otherwise fill a TMethod object and cast that to the proper "procedure of object" declaration. Don't forget the calling convention.
For more bizarre solutions you might want to have a look at (RemObjects') Pascalscript.
P.s. this is the same that you can't even call a C++ method reliably from another C++ compiler. It is not Pascal vs C++ per se.