Re: Member pointers in 0.8.1

Marcus,
awesome! That should go into the official docs for slow people like me. I remember vaguely thinking about a similar solution, but back then I think we didn't want to include lua/luabind in all of the classes that needed to be bound, but that requirement changed over time. Also, I didn't get the raw_ policy at all :)
I assume, this would work just as fine for returning shared_ptr using shared_from_this ?

Daniel,
thanks for the heads up on the downcasts! 

best,
Tony




________________________________
Von: Marcus Speight <[email protected]>
An: [email protected]
Gesendet: Freitag, den 24. April 2009, 19:22:31 Uhr
Betreff: Re: [luabind] Member pointers in 0.8.1

Define function to accept the raw state

.def("GetObject", (luabind::object(Manager::*)(Name&, lua_State*)) &Manager::GetObjectByName, raw(_2))

In you base object class add a virtual function called asLua

class Object
{
    ...
    virtual luabind::object asLua(lua_State *L) = 0;
};

The new GetObjectByName function calls the one you already have then calls the new asLua function

luabind::object Manager::GetObjectByName(Name& n, lua_State *L)
{
    Object *obj = GetObjectByName(n);
    return obj->asLua(L);
}

In derived classes override the asLua function

class Camera
{
    ...
    virtual luabind::object asLua(lua_State *L) { return luabind::object(this, L); }
};

The result is the function returns a derived type.

local l_camera = Manager::GetObject(Name("Camera"));

l_camera is of type Camera.

> Date: Fri, 24 Apr 2009 17:19:28 +0000
> From: [email protected]
> To: [email protected]
> Subject: Re: [luabind] Member pointers in 0.8.1
> 
> 
> I'd be interested in a solution for this as well. What we did as a workaorund was to add cast functions to the lua bindings for the derived classes, so you have to know that (in Lua) you receive a Object* and then convert like this: local actor = Actor.cast(myobject).
> It does feel wrong to introduce casts like this to a dynamic language, but at least it works. Ultimately, we rewrote part of our project specifically because of these problems and reimplemented some of the classes in pure lua.
> I really wish luabind was more intelligent and forgiving when it comes to (smart)pointer casts and general usage.
> Best,
> Tony
> 
> 
> ----- Ursprüngliche Mail ----
> Von: hymedia <[email protected]>
> An: [email protected]
> Gesendet: Freitag, den 24. April 2009, 19:04:53 Uhr
> Betreff: Re: [luabind] Member pointers in 0.8.1
> 
> Greetings,
> 
> This might be a no can do but you wizards out there might have an hocus
> pocus workarounds...
> 
> Let say the basic function is define like this:
> 
> .def("GetObject", (Object*(Manager::*)(Name &)) &Manager::GetObjectByName)
> 
> All good, the Manger return an Object, but many classes derived from Object
> in my C++ and my Luabind Modules follow the same structure. In c++ you can
> statically cast to the desired type... Is there a way to static cast a
> Luabind return value within a Lua script?
> 
> Something like:
> 
> local l_camera = (Camera*) Manager:GetObject(Name("Camera"));
> 
> 
> This would work But it is not really sexy...
> 
> .def("GetActor", (Actor*(Manager::*)(Name &)) &Manager::GetObjectByName)
> .def("GetCamera", (Camera*(Manager::*)(Name &)) &Manager::GetObjectByName)
> 
> thx
> 
> -----Original Message-----
> From: Ilia Trendafilov [mailto:[email protected]] 
> Sent: Tuesday, April 14, 2009 3:07 PM
> To: [email protected]
> Subject: Re: [luabind] Member pointers in 0.8.1
> 
> Problem solved! Thanks!
> 
> On Mon, Apr 13, 2009 at 10:16 PM, Daniel Wallin <[email protected]> wrote:
> > Ilia Trendafilov wrote:
> >> James Porter wrote:
> >>> Your code works for me in Luabind 0.8.1 / Lua 5.1.4 / MSVC8 SP1 with no
> >>> problems whatsoever. Is your version of Lua up to date, and did you
> >>> compile Luabind via bjam?
> >
> > Really? That's weird. It fails for me on GCC 4.3.2 as well.
> >
> >> Since you can run the code, it seems that I'm doing something wrong,
> >> but I don't have a clue what it might be. Not sure if that's relevant,
> >> boost version is 1.37 on Windows and 1.38 on Linux, built by bjam on
> >> both OSes.
> >
> > Can you try this patch, it should solve the problem:
> > ...
> > Daniel Wallin
> > BoostPro Computing
> > http://www.boostpro.com
> 
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