Quick Question: IsA or Casting?

[GuruKnight]

Which would be better if you have an actor and want to see if its a certain object?

if(myObj.IsA('MyObject'))


OR

if(MyObject(myObj) != none)

Is there any difference? I think the second would be better because you find 2 things from it. 1 is that its your object and the 2 is whether it is none or not. Does the first method also does both these things?

 

[elmuerte]

if myObj = none the first would give errors, but the first is a tiny bit more efficient

 

[Winged Unicorn]

The first method (IsA) just checks if the given Object has a certain class among its parent classes:

inline UBOOL UObject::IsA( class UClass* SomeBase ) const
{
	guardSlow(UObject::IsA);
	for( UClass* TempClass=Class; TempClass; TempClass=(UClass*)TempClass->SuperField )
		if( TempClass==SomeBase )
			return 1;
	return SomeBase==NULL;
	unguardobjSlow;
}

The second method (dynamic cast) is definately safer, because it first makes sure that the pointer to the given Object is valid, then it internally calls the first method (IsA) itself:

template<class T> T* Cast( UObject* Src )
{
	return Src && Src->IsA(T::StaticClass()) ? (T*)Src : NULL;
}

Therefore, use the second method any time you can. Use the first one only when all you have is a class name and not an actual reference.

 

[GuruKnight]

Aye, thank you.

Interesting that the 2nd calls the other internally.

 

[[SAS]Solid Snake]

I usually almost always use the the second one and that is to avoid Script Errors at all times, I am one of those coders that hate script warnings and do everything I can do avoid it. I use the IsA when I know the object I am IsA'ing is never none.