LuaGlueClassRef

[JMLX42]

Hi,

the idea is the same as described in #25 but for Lua "classes" tables. In C++, there is no way to manipulate a "class object". Yet, as Lua stores classes as tables, we can easily emulate some aspects of C++ meta-programming if we were able to get a reference to a comparable Lua class table object.

MyComponentClass = {}
function MyComponentClass:someMethod()
-- some code...
end

MyOtherComponentClass = {}
function MyOtherComponentClass:someMethod()
-- some other code...
end

cppObject:removeComponentByType(MyOtherComponentClass)

class MyCppClass
{
public:
  template <typename T>
  removeComponentByType()
  {
    // use typeid...
  }

  void
  removeComponentByTypeWrapper(LuaGlueClassRef ref)
  {
    // compare "ref"...
  }
};

So I was thinking about having a LuaGlueClassRef and the required stack<> specializations. This class should only store the things required to identify and compare Lua class bound from C++ using LuaGlue. For example, we could compare their METATABLE_CLASSIDX_FIELD field.

What do you think?

[Tomasu]

Hm, that could work.

One question though, if I added a wrapper for Lua tables, and allowed passing them to C++, would also work? I think not being able to pass tables around is probably a rather big missing feature. At any rate, adding a table wrapper is going to happen.

[JMLX42]

Well I don't pass tables from C++ to Lua. And when I'm dealing with Lua tables in C++, I actually only need somekind of comparable ref: not the actual table and its content. I just want to be able to "compare types".

Anyway we could have a LuaGlueTable object with get/set methods: those won't weight anything since they'll just mess with the Lua stack when called. Right?

I guess the two features can be implemented in a single class then...

[Tomasu]

Yeah, I meant passing tables from lua to C++.

But yeah, I see what you want.. I'm just not sure it needs to be implemented in the core like that. What about adding a global function that grabs the type from any LuaGlue object/class? then you can pass that in as a string (not sure exporting the class idx is a good idea, its an internal implementation detail, and the actual integer value will change based on the order things are added to the symtab).

[Tomasu]

Ok, I've pushed up a "typeid" function that can be called on a Class or an instance. Let me know if this works for you.

[Tomasu]

closing for now. if theres something I've missed, please reopen.