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(void*) as Parameter and @this handle

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Started by saejox May 03, 2012 04:51 PM

4 comments, last by saejox 11 years, 11 months ago

saejox

714

Author

May 03, 2012 04:51 PM

Hi,

I would like to use function such as



r = engine->RegisterObjectMethod("EventManager", "int RegisterSomeCallback(?&in ,const string &in)", asMETHODPR(EventManager, RegisterSomeCallback, (void *,const string &), int), asCALL_THISCALL);assert( r >= 0 );

Angelscript Code



class Npc

{

	 int callbackid;

	 Npc()

	 {

	 	 // pass object pointer to engine with function name

	 	 callbackid = EM.RegisterSomeCallback(@this, "CallBackFunction");

	 }



	 void CallBackFunction()

	 {

	 	 print("Success!");

	 }



	 ~Npc()

	 {

	 	 EM.UnregisterCallback(callbackid);

	 }

}

passing @this as a pointer is not possible as i figured. or am i doing it wrong?
also is ?&in correct way to register void* parameter?

thank you.

saejox

714

Author

May 03, 2012 05:08 PM

Another related question

is it possible to pass an object function's pointer to another Angelscript function or to C++ ?

WitchLord

4,834

May 03, 2012 06:29 PM

You can pass @this to a ?&in parameter. AngelScript will then pass a pointer to the handle as the argument.

Note that the ?&in parameter in AngelScript is translated to 2 distinct parameters in the registered function, the first is the void* that receives the pointer to the value, and the second is an int that receives the typeId of the value.

Manual: The variable parameter type

Your function RegisterSomeCallback must then be implemented as:



int EventManager::RegisterSomeCallback(void *ptr, int typeId, const string &methodName)

{

   // Make sure it is a handle that is received

   if( typeId & asTYPEID_OBJHANDLE )

   { 

      // Get the address of the object

      void *obj = *reinterpret_cast<void**>(ptr);



      // Get the object type

      asIObjectType *type = engine->GetObjectTypeById(typeId);



      // Get the method

      asIScriptFunction *func = type->GetMethodByName(methodName.c_str());

      if( func )

      {

         // Keep a reference to the object for the callback

         engine->AddRefScriptObject(obj, type);



         ...

      } 

   }

}

No, it is currently not possible to take the pointer of a class method in AngelScript. In a future version I'll implement something similar to delegates to support this.

AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

saejox

714

Author

May 03, 2012 07:16 PM

i thought typeid was optional and engine registers only handle if it doesn't exist. silly me.

i did it like this (might be useful for someone in the future)



int EventManager::RegisterSomeCallback(void *ptr, int typeId, const string &methodName)

{

   if( typeId & asTYPEID_OBJHANDLE )

   {

	  // cast it to asIScriptObject

	  asIScriptObject*obj = *static_cast<asIScriptObject**>(ptr); // static_cast works just fine





	  // Get the object type

	  asIObjectType *type = obj->GetObjectType(); // faster than engine->GetObjectTypeById lookup i think



	  // Get the method

	  asIScriptFunction *func = type->GetMethodByName(methodName.c_str());

	  if( func )

	  {

		 obj->AddRef() // dont need engine here neither

	  }



   }

}

Thank you. It works beautifully!

WitchLord

4,834

May 03, 2012 07:30 PM

That works too. Though you may want to add a check to make sure the handle is really to a script object, so the application doesn't crash in case the script calls the function with a handle to a registered object instead.



// Make sure the value is a handle to a script object

if( (typeId & asTYPEID_OBJHANDLE) && (typeId & asTYPEID_SCRIPTOBJECT) )

{

   ...

}

AngelCode.com - game development and more - Reference DB - game developer references
AngelScript - free scripting library - BMFont - free bitmap font generator - Tower - free puzzle game

saejox

714

Author

May 03, 2012 07:38 PM

That works too. Though you may want to add a check to make sure the handle is really to a script object, so the application doesn't crash in case the script calls the function with a handle to a registered object instead.

// Make sure the value is a handle to a script object if( (typeId & asTYPEID_OBJHANDLE) && (typeId & asTYPEID_SCRIPTOBJECT) ) { ... }

thank you.

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