Re: Luabind and passing classes

Heh, I should have tried you code before I replied....

anyhow - using std:string will work, but I looks like const char *
should work too.

I tried this using gcc -

#include <iostream>

#include "lua.hpp"
#include "luabind/luabind.hpp"
#include "luabind/operator.hpp"

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));
    }
};

int main()
{
    lua_State* L = luaL_newstate();
    luaL_openlibs(L);
    using namespace luabind;
    open(L);

    TestClass::configureLuaObject(L);

    if (luaL_dostring(L, "t = TestClass('My Test')\n"
			 "print(t:getString())") == 1)
    {
        std::cout
            << "Couldn't run Lua program: "
            << lua_tostring(L, -1)
            << std::endl;
    }
}

and it worked.

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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