Re: Luabind and passing classes

If you change to returning a std::string, rather than a const char *, it
should work.  I'm not sure, but from memory Luabind has a 'built-in'
converter from std:string to a Lua string.

You can return a const char * if you really need to, but I think it will
just appear as Lua userdata? Not sure.  What was the error you got?
Unless you're happy with std::string, then it doesn't matter. ;-)

Nigel

On Wed, 2010-07-21 at 19:42 -0700, Nathaniel Lewis wrote:

> Thanks I spent a bit and got what I wanted working sort of.  How do you
> you return strings from a exposed function?  I got the exposing working
> fine and I can pass a string as a parameter but how do I get it as a
> result. the class (part of testing) is
> 
> class TestClass {
>     std::string myString;
> public:
>     TestClass() {
>         myString = "Not Initalized";
>     }
>     TestClass( const char* aString ) {
>         myString = std::string(aString);
>     }
>     void setString( const char* aString ) {
>         myString = std::string(aString);
>     }
>     const char* getString( void ) {
>         return myString.c_str();
>     }
>     void printString( void ) {
>         std::cout << myString << std::endl;
>     }
>     static void configureLuaObject(lua_State* lVM) {
>         luabind::module(lVM) [
>             luabind::class_<TestClass>("TestClass")
>                 .def(luabind::constructor <> ())
>                 .def(luabind::constructor<const char*>())
>                 .def("setString", &TestClass::setString)
>                 .def("getString", &TestClass::getString)
>                 .def("printString", &TestClass::printString)
>         ];
>     }
>     void callFunction(lua_State* lVM) {
>         luabind::call_function<void>(lVM, "AFunction",
> boost::ref(this));
>     }
> };
> 
> getString throws an error when run.
> 					Nathaniel
> 
> On Thu, 2010-07-22 at 13:40 +1200, Nigel Atkinson wrote:
> > Hi Nathaniel,
> > 
> > Short answer: Yes.
> > 
> > If you bind a class using Luabind it can be passed to Lua functions as
> > a parameter.  When you bind a class you do not need to bind the
> > class's constructor.  Omitting the constructor prevents your Lua
> > script from being able to instantiate that particular class, however
> > Lua can otherwise use instances passed to it from C++.
> > 
> > I do this quite often with singleton classes.
> > 
> > Nigel Atkinson
> > 
> > On Wed, 2010-07-21 at 16:53 -0700, Nathaniel Lewis wrote: 
> > > I was reading through some tutorials and I had a question unanswered.
> > > How do I pass a specific class to Lua?  I have a class that represents a
> > > world in my game engine and I need some way to talk with it from Lua.  I
> > > think LuaBind is the answer but I don't know.  I would never want to
> > > create the class from Lua.  Instead I would want to pass a reference to
> > > the one created on the c++ side to Lua and then call functions inside of
> > > it.  Is this possible with LuaBind?  Basically a simple script would
> > > look like this
> > > 
> > > -- called when map is loaded by engine --
> > > function Init (worldInstance) 
> > >     -- do stuff --
> > > end
> > > 
> > > -- called after every frame is rendered --
> > > Update = coroutine.wrap( function (worldInstance, timeSinceLastFrame)
> > >     while true do
> > > 	-- do stuff + call coroutine.yield() when waiting for things --
> > >     end
> > > end)
> > > 						Nathaniel
> > > 
> > > 
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