function pointer

**durban** · 10-08-2005

I'm having a problem with a function pointer. The function pointer is in a struct and is being set to a function in a derived class(the class name isn't certain).

Code:

typedef struct StateManager
{
	D3DRENDERSTATETYPE RenderState[10];
	DWORD Value[10];
	void (*render)(void); // FUNCTION POINTER

Code:

virtual void __cdecl Render(); //FUNCTION DECLARATION

RenderResources is the predefined struct. Render is the overloaded Render function.

Code:

RenderResources->render = Render;

And the error:

Code:

error C2440: '=' : cannot convert from 'void (__cdecl ArkTest::* )(void)' to 'void (__cdecl *)(void)'

I'm guessing I need to change the function pointer declaration to contain ArkTest:: but I don't want to do that because there's no certainty the overloaded function will be ArkTest. However, I'm new to function pointers and I'm probably missing something. Any Ideas?

**grumpy** · 10-08-2005

You want a pointer to member function, not a pointer to function. __cdecl is also a compiler specific extension, which I'll ignore.

To get a pointer to member function use;

Code:

class X
{
      void (X::*render)();

      public:
         X() {render = &X::Render;};
         void Render();
         void DoRender() {this->(*render)();};
};

**Salem** · 10-08-2005

A really good and detailed explanation
http://www.newty.de/fpt/index.html

**durban** · 10-08-2005

AYE! Thanks for the reply, but I don't think you read my whole post. Now, the problem is..I don't know the member's class. =X Is there any way to make a pointer to a class member that you don't know? Such as a derived class =)

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