LUA API for my simple engine

Hi there! I´ve been developing a simple engine for quite a time now and now I am at the point where it comes inevitable to either hardcode a game or implement a LUA API for the engine, so that I can do most of the game stuff in LUA. So I´ve went along read quite a big part of the LUA documentation, and finally came to the conclusion that using SWIG to build my LUA API would be a good move. However I´ve come to a dead point somehow: I´ve coded 2 simple classes that wrap my base entity class and the class for movables: Entity wrapper: L_Entity.h


class L_Entity
{
public:
	L_Entity(){this->m_pEntity = NULL;}
	L_Entity(PUKE::Logic::Entity *e){this->m_pEntity = e;}
	
	~L_Entity(){this->m_pEntity = NULL;}

	virtual void SetName(char* n)
	{
		if(this->m_pEntity)
		{
			this->m_pEntity->SetName(LPCTSTR(n));
		}
	}
	virtual char* GetName()
	{
		if(this->m_pEntity)
		{
			return (char*)this->m_pEntity->GetName();
		}
		return "";
	}

	virtual void SetPosition(float x, float y, float z)
	{
		if(this->m_pEntity)
		{
			this->m_pEntity->SetPosition(x,y,z);
		}
	}


	virtual float GetPositionX()
	{
		if(this->m_pEntity)
		{
			return this->m_pEntity->GetPosition().x;
		}
		return 0.f;
	}

	virtual float GetPositionY()
	{
		if(this->m_pEntity)
		{
			return this->m_pEntity->GetPosition().y;
		}
		return 0.f;
	}

	virtual float GetPositionZ()
	{
		if(this->m_pEntity)
		{
			return this->m_pEntity->GetPosition().z;
		}
		return 0.f;
	}

	virtual void SetState(int newState)
	{
		if(this->m_pEntity)
		{
			this->m_pEntity->SetState(newState);
		}
	}

	virtual int	GetState()
	{
		if(this->m_pEntity)
		{
			return this->m_pEntity->GetState();
		}
		return -1;
	}

	virtual void PerformAction(int action)
	{
		if(this->m_pEntity)
		{
			this->m_pEntity->GetController()->PerformAction(action);
		}
	}


protected:
	PUKE::Logic::Entity *m_pEntity;
};

Movable wrapper: L_Movable.h


class L_Movable : public L_Entity
{
public:
	L_Movable() : L_Entity(){}
	L_Movable(PUKE::Logic::Movable* m) : L_Entity(m){}

	void MoveTo(float x, float y, float z, float speed)
	{
		if(this->m_pEntity)
		{
			((PUKE::Logic::Movable*)this->m_pEntity)->MoveTo(x,y,z,speed);
		}
	}
	
	void MoveToTimed(float x, float y, float z, float time)
	{
		if(this->m_pEntity)
		{
			((PUKE::Logic::Movable*)this->m_pEntity)->MoveToTimed(x,y,z,time);
		}
	}
};

Additionally I have a simple function that returns a pointer to the Entity with a specific name, which is wrapped in this function: L_StaticFunctions.h


static L_Entity GetEntity(LPCTSTR name)
{
	if(PUKE::pCurrentScene)
	{
		PUKE::Logic::Entity* e = PUKE::pCurrentScene->GetEntityByName(name);
		switch(e->GetType())
		{
		case MOVABLE:
			return L_Movable((PUKE::Logic::Movable*)e);
		
		default:
			return L_Entity(e);
		}
	}
	return L_Entity();
}

Now I´ve created a simple SWIG file like this:


%module PUKE
%include <windows.i>

%include "L_StaticFunctions.h"
%include "L_Entity.h"
%include "L_Movable.h"

So far, so good... after adding some #include's and a using namespace into the create PUKE_wrap.cxx everything compiled fine. Now using L_Entity, L_Movable and the static GetEntity should work. Have a look at the simple LUA-function I created:


function Button1OnPush()
	t = PUKE.L_Movable()
	t:PerformAction(123)
	
	test = PUKE.L_Entity()
	test:PerformAction(8)
	
	door = PUKE.GetEntity("Door01")
	door:PerformAction(8)
	door = GetEntity("Door02")
	door:PerformAction(8)
end

This function works until the line door:PerformAction(8). Notice that t = PUKE.L_Movable() and t:PerformAction(123) works as expected. PUKE.GetEntity(...) seems to work, too. At least the C++-function returns a valid Entity. However door:PerformAction(8) results in the following error: map.lua:17: attempt to index global 'door' (a userdata value) So, all in all my questions are: a) Does anybody have a clue why that error occurs, although L_Movable seems to be available in LUA? b) As the PUKE_wrap.cxx is unreadable, as the comment at its top also states, I would love to read a tutorial on wrapping C++ classes for LUA myself, perhaps that will produce more readable code, although more work, so I´d appreciate using SWIG if I get it to work correctly. Thx for reading and for help and sry for posting that much source, but I think I´ve got everything necessary. If not, feel free to ask.

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