About CScriptHandle

Author

714

June 18, 2012 09:31 PM

Hi,

i use CScriptHandle like this



    CScriptHandle handle;

    asIScriptObject *obj = Npcs[id]->scriptObject->object;

    handle.opAssign(obj, Npcs[id]->scriptObject->type->GetTypeId());

    obj->Release();

    return handle;

script



TestShip @npc = cast<TestShip@>(AI.GetNpcScriptHandle(second.id));

            if(npc is null)

                dbg("FAIL!");

first question:

asIScriptObject stored in CScriptHandle is already created way before being used by CScriptHandle.
i continuously use asIScriptObject to find which script object is associated with npc.
i dont get the call obj->Release(); (without it, Kept by application error)
if CScriptHandle holds a ref wont it be released when it goes out of scope, why do i need to call release on my precious object?

second question:

TestShip class is inherited from NpcShip
so when i cast it like this



NpcShip @npc = cast<NpcShip@>(AI.GetNpcScriptHandle(second.id));

@npc is always null, it cant cast it.
i am assuming this expected behaviour.
if so, how should i achieve this cast? (very important since i cant really know object type, only its base class)

Thank you.

WitchLord

4,860

June 19, 2012 01:28 PM

Question 1:

I agree with you. Calling Release() shouldn't be needed here. I'll have to check what is happening.

As a side note. I'll need to implement a Set() method to be used from the application instead of opAssign(). opAssign() only works if there is an active context (in your case I guess there is as you didn't get a null-pointer-access exception).

Question 2:

The CScriptHandle doesn't have the intelligence yet to see that the TestShip also is a NpcShip. The CScriptHandle::opCast() method needs to implement this with call to engine->IsHandleCompatibleWithObject().

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WitchLord

4,860

June 19, 2012 03:18 PM

I tested the scenario for returning a CScriptHandle, the following function is working properly:





static CScriptHandle ReturnRef()

{

  asIScriptContext *ctx = asGetActiveContext();

  asIScriptEngine *engine = ctx->GetEngine();

  asIScriptModule *mod = engine->GetModule("test");

  int typeId = mod->GetTypeIdByDecl("CTest");



  asIScriptObject *obj = reinterpret_cast<asIScriptObject *>(engine->CreateScriptObject(typeId));



  CScriptHandle ref;

  ref.opAssign(obj, typeId);



  // Need to release our reference as the CScriptHandle counts its own, and we will not keep our reference

  obj->Release();



  return ref;

}

The function is registered with:





engine->RegisterGlobalFunction("ref @ReturnRef()", asFUNCTION(ReturnRef), asCALL_CDECL);

and the script that called it looks like this:





class CTest

{

  int val;

  CTest()

  {

    val = 42;

  }

}

void func()

{

  ref @r = ReturnRef();

  assert( r !is null );

  CTest @t = cast<CTest>(r);

  assert( t !is null );

  assert( t.val == 42 );

}

Observe, that in this function I really do have to call Release() because the application creates the instance in the call and won't keep a reference to the object that will be returned by the CScriptHandle.

In your case, as the application will hold on to the reference even after the return, the Release() method should not be called.

My guess is that the Release() is missing in some other place, probably when you're cleaning up your C++ Npcs, which is when the script object needs to be destroyed too.

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saejox

Author

714

June 19, 2012 07:20 PM

you are right, physics callback of a projectile was holding a reference to npc even though it should not.
Thank you.

on the second issue.
i try to handle the cast issue by using CScriptAny, since i saw in implementation that it checks for IsHandleCompatibleWithObject



	int tid = Npcs[id]->scriptObject->type->GetTypeId();

	tid |= asTYPEID_OBJHANDLE; // make type id a handle,

	asIScriptObject **o = &obj; // CScriptAny expects a handle, so give it a pointer to a pointer, it will derefence it as i understand it

	CScriptAny *myAny = new CScriptAny(o, tid, engine);

	return myAny;

script



NpcShip @npc;		

any a = AI.GetNpcScriptHandleAsAny(second.id);

a.retrieve(@npc); // returns false

this fails at IsHandleCompatibleWithObject. doesnt think TestShip is an NpcShip. ( script side casting works)

should i stop trying to work around it till you finish CScriptHandle

edit:



TestShip @npc; // not NpcShip (base)

any a = AI.GetNpcScriptHandleAsAny(second.id);

a.retrieve(@npc);

works. but,
NpcShip @npc; a.retrieve(@npc); doesnt

WitchLord

4,860

June 20, 2012 02:50 AM

I just checked in the changes for CScriptHandle. Besides supporting polymorphing for script classes I also made some other changes for the C++ interface that should hopefully make slightly easier to use.

You can find it at the head revision in the SVN.

Let me know if it works or if you face any troubles with it.

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saejox

Author

714

June 20, 2012 07:01 AM

Thank you for your trouble, but it doesnt work

it is same problem as i mentioned in my previous post about CScriptAny.

IsHandleCompatibleWithObject does not accept types as compatible.
CScriptAny is stuck at the same place too

here is how class inheritance looks like,



class NpcBase

{

	 // npc related stuff, like handles to c++ objects

};



class NpcShip : NpcBase

{

	 // ship related stuff

};



class TestShip : NpcShip

{

	 // individual npc ship

};

here i cast in script, this works



TestShip ship;

    TestShip @shipHandle = @ship;



    NpcShip @baseShip;

    @baseShip = cast<NpcShip>(shipHandle);



    if(baseShip !is null)

	  dbg("success!");

prints success

i use it like this



NpcShip @npc;

@npc = cast<NpcShip>(AI.GetNpcScriptHandle(second.id)); // GetNpcScriptHandle returns TestShip@

Casting it to NpcBase also does not work. Casting to TestShip continues to work with new Cast method.

i thought maybe i made a mistake in my c++ code, so i tried this script



	 TestShip ship;

	 TestShip @handle = @ship;

    any shipAny;

    shipAny.store(@handle);

    NpcShip @base;

    shipAny.retrieve(@base);



    if(base is null)

	  dbg("Fail");

prints Fail.

now i m pretty sure IsHandleCompatibleWithObject doesnt return true when it should.

sorry for the long verbose code

WitchLord

4,860

June 20, 2012 02:04 PM

Yes, it's possible the method has a bug. Yesterday I only tested with Interfaces. I'll add a test for inherited classes too.

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WitchLord

4,860

June 20, 2012 03:14 PM

You were right. IsHandleCompatibleWithObject was completely ignoring the inheritance.

It's just a small change to fix this:





bool asCScriptEngine::IsHandleCompatibleWithObject(void *obj, int objTypeId, int handleTypeId) const

{

  // if equal, then it is obvious they are compatible

  if( objTypeId == handleTypeId )

    return true;



  // Get the actual data types from the type ids

  asCDataType objDt = GetDataTypeFromTypeId(objTypeId);

  asCDataType hdlDt = GetDataTypeFromTypeId(handleTypeId);



  // A handle to const cannot be passed to a handle that is not referencing a const object

  if( objDt.IsHandleToConst() && !hdlDt.IsHandleToConst() )

    return false;



  if( objDt.GetObjectType() == hdlDt.GetObjectType() )

  {

    // The object type is equal

    return true;

  }

  else if( objDt.IsScriptObject() && obj )

  {

    // There's still a chance the object implements the requested interface

    asCObjectType *objType = ((asCScriptObject*)obj)->objType;

    if( objType->Implements(hdlDt.GetObjectType()) )

      return true;



// ---> Add this

    // It may also be an inheritance

    if( objType->DerivesFrom(hdlDt.GetObjectType()) )

      return true;

  }



  return false;

}

I'll have this fix checked in tonight.

Regards,
Andreas

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saejox

Author

714

June 21, 2012 02:56 PM

thank you casting works.

but a new bug appears

this is from test_addon_scripthandle.cpp file



r = ExecuteString(engine, "ref @r = ReturnRef(); \n"

		  "assert( r !is null ); \n"

						    "CTest @t = cast<CTest>(r); \n"

		  "assert( t !is null ); \n"

		  "assert( t.val == 42 ); \n", mod);

this test works.

but when change it like that



r = ExecuteString(engine, "ref @r = ReturnRef(); \n"

		  "assert( r !is null ); \n"

						    "CTest @t = cast<CTest>(ReturnRef()); \n" // use ReturnRef() directly

		  "assert( t !is null ); \n"

		  "assert( t.val == 42 ); \n", mod);

it causes an assertion at this line :
line number: 917 as_compiler.cpp
asASSERT( tempVariables.GetLength() == 0 );

WitchLord

4,860

June 21, 2012 03:33 PM

Thanks. This is probably a bug with the asOBJ_ASHANDLE feature. I'll look into it.

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