luabind-user — luabind's official mailing list

[luabind] Test for key on luabind class (userdata vs table?)

[Glen F. <hol...@gm...>]

Hi there, I know it's possible to set "properties" on luabind classes in Lua.  You can set and get these keys, no problem.  However, it doesn't seem possible to "get" (or test for the existence of) an unset key -- you'd expect it to return 'nil', but it crashes.  Is there a way to test a luabind class for the existence of a key (as though it were a table), without crashing?  Here is a made-up example:

function testKey(obj, key)
    if obj[key] then
        print(type(obj) .. " key: '" .. key .. "' value: " .. obj[key])
    else
        print(type(obj) .. " key: '" .. key .. "' doesn't exist.")
    end
end

class 'MyClass'
MyClass.someFlag = 5
function MyClass:__init(name)
    self.name = name
end

-- Test on an instance of the class:
a = MyClass('example')
testKey(a, 'name')
testKey(a, 'doesNotExist') -- not an error to access an unset key; simply returns nil
testKey(a, 'someFlag')
a.someFlag = -12
testKey(a, 'someFlag')

-- Now do a similar test on the class itself (not an instance):
testKey(MyClass, 'someFlag') -- works fine; the key has already been set

-- But for undefined keys, it fails (if MyClass were a table instead of
-- a userdata (class), you'd expect it to simply return nil).
testKey(MyClass, 'doesNotExist') -- crash

So, is there a way I can test if a luabind class has a particular key?  (I'm using Lua-derived C++ classes, but I have the same problem even with simple luabind classes, as shown in the above simple example).

Thanks,
Glen.

Re: [luabind] I want to please unsubscribe from this list

[Michael S. <mic...@tu...>]

Doesn't the unsubscribe-function on the admin page work?

[luabind] I want to please unsubscribe from this list

[Maha A. <mah...@gm...>]

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Re: [luabind] References to native types

[Michael S. <mic...@tu...>]

Hello again,
digging through the list I found this issue to pop up again and again.
People were trying to use refs to native types, or there were
complaining why luabind wouldn't support it etc.. Maybe it would be wise
to add a paragraph to the documentation stating that is just not
possible to implement that, since lua does not know about
references/pointers?
The only thing that I can imagine one could do would be to provide an
opt-in type boxing support. So you could inject boxed native types into
lua that could be unboxed into references on the c++ side again (I think
this is quite similar to what Java has?). And some way to box native
types on the lua side to, to simulate references. One would then have to
differ between lua and c++ boxes, because c++ boxes would contain
pointers to a c++ value, whereas boxes created in lua would have a true
datamember...
The unboxing converter would then have to differ between c++ boxes and
lua boxes, because the latter would have to write back to the table,
whereas the former supplied the true pointer and wouldn't have to do
anything.
But any way, we'd have to manually box and unbox the types in native and
in lua code. So I really doubt that it's worth the great effort that is
necessary to implement that.

Michael

[luabind] References to native types

[Michael S. <mic...@tu...>]

Hi there,
I was playing around with the rvalue reference stuff whereby I broke a
test case, which happened to declare a function to lua with the
signature "int(int&)".
Now you could make that work by registering "int" as a class and when
passing in a value by reference, it would wrap that one up to a userdata
object. However when you do that, you basically disable the ability to
call functions on the lua side that accept numbers. My question is,
should registering functions taking references to native types even be
allowed?

I think I will have to somewhate differ in all calls between native&user
defined types. Because for example when you call into lua with a rvalue
ref to a user defined type, it could move it to the internal pointer
holder (and on the other end it could move it out, if there was a flag
indicating rvalue reference), however for native types they must be
treated as per-value under all circumstances (probably the passing is
broken in current head because of that, call_function took a const& of
all parameters and the default_converter was somehow "optimized" to
catch const int& (but not int&!) and treat it by value. This stuff is
pretty fragile and I intend to replace it by something that is
reasonably understandable).

Michael

Re: [luabind] Alternative fork for C++11

[Willi S. <wi...@sc...>]

I downloaded it sometime in the afternoon - judging from your name 
you're probably German as well so we likely share a timezone, so chances 
are I didn't have the latest version. I'll try again later, using 4.8 as 
well.

Circular dependencies are indeed something I thought of as well but 
didn't want to investigate at the time.

Willi

Re: [luabind] Alternative fork for C++11

[Michael S. <ms...@tu...>]

Hello Willi,

which version did you use on which compiler? I had exactly these error 
messages before getting it compatible to gcc 4.8.1 yesterday evening. 
This was a problem that started, because MSVC delays template 
instantiation (contra the standard) and so conforming compilers need 
certain function definitions earlier in cases. But including the 
definitions led to a circular header dependency, which never ends well. 
I fixed that one last evening, so I'm curious if you used the latest master?

Michael

Re: [luabind] Alternative fork for C++11

[Willi S. <wi...@sc...>]

I've fiddled with it for a while but couldn't get it to compile with the 
Android NDK. Got a couple of errors, like one about 
luabind::get_back_reference() not being found in pointer_converter.hpp 
although it clearly includes back_reference.hpp. Strange.

Well, I'll use the Lua C API for now, using experimental C++11-based 
libraries might not be the best thing to do in your first Android NDK 
program.

Willi

Re: [luabind] Alternative fork for C++11

[Willi S. <wi...@sc...>]

Hi,

just wanted to say thank you for this. I'll probably give this a try 
soon-ish and report back. (Any problems I encounter will go to the 
github issue tracker, that what it's for after all.)

Willi

Re: [luabind] Alternative fork for C++11

[Michael S. <mic...@tu...>]

Hello,
thank you so much for the input, I will work on it.

Michael

PS: Do you mind me contacting you directly in case if questions? Mustn't
have all the noise here for implementation details, I figure.

Re: [luabind] Alternative fork for C++11

[Lorenzo P. <bla...@gm...>]

Actually it is a very good thing to require an extra flag, as c++11 
doesn't only add stuff but changes the behaviour of some subtleties.

On 09/26/2013 05:14 PM, Michael Steinberg wrote:
> Gnarg!
> I will try to find out how to set that with the CMake files. This was
> the first CMake project I used and I didn't think about other compilers
> might need an extra flag for c++11. Many more beginner's mistakes to come!
>
> Michael
>
> ------------------------------------------------------------------------------
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Re: [luabind] Alternative fork for C++11

[Lorenzo P. <bla...@gm...>]

Right now I'm busy so I can't fix all the problems, but here's something 
that might be interesting to you.
A patch for some trivial problems with path names (replace \ with /, 
which is cross-platform) and the -std=c++11 flag: 
http://pastebin.com/maSTChZy
A log of "make -k" to spot the compilation errors on all the compile 
units: http://pastebin.com/KgjZtULV
I urge you to also add a newline at the end of the source files, not 
having that is a bit annoying on linux because basically every tool try 
to add it, and it's general wisdom to put them otherwise "some programs 
might not work".

On 09/26/2013 05:14 PM, Michael Steinberg wrote:
> Gnarg!
> I will try to find out how to set that with the CMake files. This was
> the first CMake project I used and I didn't think about other compilers
> might need an extra flag for c++11. Many more beginner's mistakes to come!
>
> Michael
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> luabind-user mailing list
> lua...@li...
> https://lists.sourceforge.net/lists/listinfo/luabind-user

Re: [luabind] Alternative fork for C++11

[Lorenzo P. <bla...@gm...>]

Hold on, I have already fixed it, plus another thingie. I'll share the 
patch in moments
On 09/26/2013 05:14 PM, Michael Steinberg wrote:
> Gnarg!
> I will try to find out how to set that with the CMake files. This was
> the first CMake project I used and I didn't think about other compilers
> might need an extra flag for c++11. Many more beginner's mistakes to come!
>
> Michael
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> luabind-user mailing list
> lua...@li...
> https://lists.sourceforge.net/lists/listinfo/luabind-user

Re: [luabind] Alternative fork for C++11

[Michael S. <mic...@tu...>]

Gnarg!
I will try to find out how to set that with the CMake files. This was
the first CMake project I used and I didn't think about other compilers
might need an extra flag for c++11. Many more beginner's mistakes to come!

Michael

Re: [luabind] Alternative fork for C++11

[Lorenzo P. <bla...@gm...>]

It doesn't seem to set the -std=c++11 flag

On 09/26/2013 04:51 PM, Michael Steinberg wrote:
> Hello,
>>   Do I just compile all the .cpp files?
> the project comes with CMake files that should probably be able to set
> up the project files for your build environment (It was very simple here
> on windows). You will need a version of the lua library however.
>
> Michael
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> luabind-user mailing list
> lua...@li...
> https://lists.sourceforge.net/lists/listinfo/luabind-user

Re: [luabind] Alternative fork for C++11

[Michael S. <mic...@tu...>]

Hello,
> I believe it reduces the codebase ? It
> should make the code a lot clearer also, allowing for more third party
> contributions.
Lots of old code has gone, the statistics are about +4k -5k lines. Note
that this includes my replacement for boost::mpl usage (boost::mpl +
boost::lexical_cast are really big buggers and noone seems to care to
make c++11-ready) and other boost stuff, so it could have been even less
(plus the meta header in the end provides much more than I used at the
end). But I fear that I might have broken stuff all over the place, so
this needs testing and the provided tests do not cover the whole code.
I tried to make the stuff clearer, if anybody has improvement ideas,
I'll gladly accept patches (when I find out how to apply them :D)/ideas.
Other than that I'm watching the other repositories and try to port
their patches.

Michael

Re: [luabind] Alternative fork for C++11

[Michael S. <mic...@tu...>]

Hello,
>  Do I just compile all the .cpp files?
the project comes with CMake files that should probably be able to set
up the project files for your build environment (It was very simple here
on windows). You will need a version of the lua library however.

Michael

Re: [luabind] Alternative fork for C++11

[Lorenzo P. <bla...@gm...>]

Looks interesting.
I could test with gcc 4.8.1 and possibly even clang on Mac OSX 10.8, but 
I'm not familiar with the original build method of luabind, I don't know 
if I should mimic it. Do I just compile all the .cpp files?

On 09/26/2013 04:31 PM, Michael Steinberg wrote:
> Hello,
> I have so far been developing privately on a fork of Ryan Pavlik's
> luabind version (https://github.com/decimad/luabind-deboostified) to
> make it independent of boost and use variadic templates and c++11
> constructs unconditionally. With the advent of Visual C++ 2013 RC I felt
> it was time to tame the beast down in order to not cripple Intellisense
> by its pure complexity of all boost preprocessor magic going on there,
> but maybe there is something in it for users of different compilers.
> I basically replaced the policy system and reworked all the
> calling-wrapper-code while trying to maintain test stability (adapting
> the tests where I found a breaking change was farvorable).
> Now I don't want to urge anyone using it (it would even create some
> porting work, as it is not 100% source compatible), but I want to ask if
> anyone could take the time to test if it compiles and tests ok on other
> c++11 compilers or if I made it unbuildable by accident (maybe even
> giving hints of what is wrong). If anyone ever feels like he would like
> to use a c++11-version, I would like to contribute back a working thing
> (or at least try to offer it).
>
> With kind regards,
> Michael
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> luabind-user mailing list
> lua...@li...
> https://lists.sourceforge.net/lists/listinfo/luabind-user

Re: [luabind] Alternative fork for C++11

[Teto <mat...@gm...>]

That's truly awesome.  I had started myself a port of luabind to C++11
 but had given up in front facing the huge amount of work needed.
I won't have time to check this anytime soon but I will in a few
months and give you feedback. I believe it reduces the codebase ? It
should make the code a lot clearer also, allowing for more third party
contributions.

Thanks a lot for your work.

Matt

On Thu, Sep 26, 2013 at 4:31 PM, Michael Steinberg
<mic...@tu...> wrote:
> Hello,
> I have so far been developing privately on a fork of Ryan Pavlik's
> luabind version (https://github.com/decimad/luabind-deboostified) to
> make it independent of boost and use variadic templates and c++11
> constructs unconditionally. With the advent of Visual C++ 2013 RC I felt
> it was time to tame the beast down in order to not cripple Intellisense
> by its pure complexity of all boost preprocessor magic going on there,
> but maybe there is something in it for users of different compilers.
> I basically replaced the policy system and reworked all the
> calling-wrapper-code while trying to maintain test stability (adapting
> the tests where I found a breaking change was farvorable).
> Now I don't want to urge anyone using it (it would even create some
> porting work, as it is not 100% source compatible), but I want to ask if
> anyone could take the time to test if it compiles and tests ok on other
> c++11 compilers or if I made it unbuildable by accident (maybe even
> giving hints of what is wrong). If anyone ever feels like he would like
> to use a c++11-version, I would like to contribute back a working thing
> (or at least try to offer it).
>
> With kind regards,
> Michael
>
> ------------------------------------------------------------------------------
> October Webinars: Code for Performance
> Free Intel webinars can help you accelerate application performance.
> Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from
> the latest Intel processors and coprocessors. See abstracts and register >
> http://pubads.g.doubleclick.net/gampad/clk?id=60133471&iu=/4140/ostg.clktrk
> _______________________________________________
> luabind-user mailing list
> lua...@li...
> https://lists.sourceforge.net/lists/listinfo/luabind-user

[luabind] Alternative fork for C++11

[Michael S. <mic...@tu...>]

Hello,
I have so far been developing privately on a fork of Ryan Pavlik's
luabind version (https://github.com/decimad/luabind-deboostified) to
make it independent of boost and use variadic templates and c++11
constructs unconditionally. With the advent of Visual C++ 2013 RC I felt
it was time to tame the beast down in order to not cripple Intellisense
by its pure complexity of all boost preprocessor magic going on there,
but maybe there is something in it for users of different compilers.
I basically replaced the policy system and reworked all the
calling-wrapper-code while trying to maintain test stability (adapting
the tests where I found a breaking change was farvorable).
Now I don't want to urge anyone using it (it would even create some
porting work, as it is not 100% source compatible), but I want to ask if
anyone could take the time to test if it compiles and tests ok on other
c++11 compilers or if I made it unbuildable by accident (maybe even
giving hints of what is wrong). If anyone ever feels like he would like
to use a c++11-version, I would like to contribute back a working thing
(or at least try to offer it).

With kind regards,
Michael

Re: [luabind] How to get Lua class name from C++ class?

[Glen F. <hol...@gm...>]

Okay, thanks, that works.  I also need to do a pop afterwards, or the stack keeps growing, right? (Seems to be the case, judging by printing out lua_gettop(L) before and after the method.)


>     luabind::object(L, &foo).push(L);
>     // Note: -1 instead of lua_gettop(L) would not work in the following line
>     // because of a bug in luabind::argument's ctor.
>     luabind::argument myArg(luabind::from_stack(L, lua_gettop(L)));
>     luabind::class_info info = luabind::get_class_info(myArg);


    ::lua_pop(L, 1);

Great, thanks -- I guess my problems were because of that bug you mention, because I was using -1 in luabind::argument's ctor.  Didn't know there was any problem with that.

Glen.

On Aug 28, 2013, at 6:23 PM, Christian <cn...@gm...> wrote:

> You are right, argument has no constructor that takes a C++ object, sorry. But using push() and from_stackworks, as in the following example (tested):
>  
> #include <luabind/luabind.hpp>
> #include <luabind/class_info.hpp>
>  
> #include <iostream>
>  
> class Foo {};
>  
> int main()
> {
>    lua_State* L = luaL_newstate();
>     luabind::open(L);
>     luabind::module(L) [
>         luabind::class_<Foo>("LuaFoo")
>     ];
>    
>     Foo foo;
>    
>     luabind::object(L, &foo).push(L);
>     // Note: -1 instead of lua_gettop(L) would not work in the following line
>     // because of a bug in luabind::argument's ctor.
>     luabind::argument myArg(luabind::from_stack(L, lua_gettop(L)));
>     luabind::class_info info = luabind::get_class_info(myArg);
>     std::cout << info.name << '\n'; // Prints "LuaFoo".
> }
>  
>  
> From: Glen Fraser [mailto:hol...@gm...] 
> Sent: Wednesday, August 28, 2013 5:38 PM
> To: lua...@li...
> Subject: Re: [luabind] How to get Lua class name from C++ class?
>  
> Thanks, Christian, but I didn't manage to get anything to work in the way you describe.  I can't seem to simply substitute 'object' with 'argument'…  I also tried using myObject.push(L), then using the "from_stack" referenced argument to call get_class_info(), then doing a lua_pop(), but that just crashes on me (a bit later on)…and before that, it hasn't returned the correct class_info structure.  I think I'd need to see a simple example, sorry.
>  
> On the other hand, the "hacky" code from Eduard (see his earlier reply) does seem to work fine, as does another approach I came up with, where I just use luabind::call_function() to call the bound "class_info" function in Lua, then get the class_info structure by doing object_cast on the returned object.  Of course, this may be (?) a bit less efficient than doing the direct stack-fiddling you guys suggest, but it works.
>  
> Thanks,
> Glen.
>  

Re: [luabind] How to get Lua class name from C++ class?

[Christian <cn...@gm...>]

You are right, argument has no constructor that takes a C++ object, sorry. But using push() and from_stack works, as in the following example (tested):

 

#include <luabind/luabind.hpp>

#include <luabind/class_info.hpp>

 

#include <iostream>

 

class Foo {};

 

int main()

{

   lua_State* L = luaL_newstate();

    luabind::open(L);

    luabind::module(L) [

        luabind::class_<Foo>("LuaFoo")

    ];

    

    Foo foo;

    

    luabind::object(L, &foo).push(L);

    // Note: -1 instead of lua_gettop(L) would not work in the following line

    // because of a bug in luabind::argument's ctor.

    luabind::argument myArg(luabind::from_stack(L, lua_gettop(L)));

    luabind::class_info info = luabind::get_class_info(myArg);

    std::cout << info.name << '\n'; // Prints "LuaFoo".

}

 

 

From: Glen Fraser [mailto:hol...@gm...] 
Sent: Wednesday, August 28, 2013 5:38 PM
To: lua...@li...
Subject: Re: [luabind] How to get Lua class name from C++ class?

 

Thanks, Christian, but I didn't manage to get anything to work in the way you describe.  I can't seem to simply substitute 'object' with 'argument'…  I also tried using myObject.push(L), then using the "from_stack" referenced argument to call get_class_info(), then doing a lua_pop(), but that just crashes on me (a bit later on)…and before that, it hasn't returned the correct class_info structure.  I think I'd need to see a simple example, sorry.

 

On the other hand, the "hacky" code from Eduard (see his earlier reply) does seem to work fine, as does another approach I came up with, where I just use luabind::call_function() to call the bound "class_info" function in Lua, then get the class_info structure by doing object_cast on the returned object.  Of course, this may be (?) a bit less efficient than doing the direct stack-fiddling you guys suggest, but it works.

 

Thanks,

Glen.

 

On Aug 28, 2013, at 4:07 PM, "Christian" <cn...@gm...> wrote:





Just replace luabind::object with luabind::argument in your code. They work both the same, only that the first stores the referenced object in the registry, while the latter just leaves it on the stack.

 

If you ever have to convert one into another, just use the ones push() method and the others from_stack constructor (but avoid relative indices with luabind::argument).

 

From: Glen Fraser [mailto:holaglen@ <http://gmail.com> gmail.com] 
Sent: Wednesday, August 28, 2013 1:09 PM
To:  <mailto:lua...@li...> lua...@li...
Subject: [luabind] How to get Lua class name from C++ class?

 

Hello there, I'm using luabind and trying to get the Lua subclass name from an instance of the base class in C++.

 

I want to use get_class_info(), but it expects an "argument" rather than an "object".  Perhaps there is a better way to do this, besides trying to figure out how to convert a luabind::object into a luabind::adl::argument…  Here is some example code that should illustrate the problem:

 

class BaseClass {

public:

    virtual ~BaseClass() {}

    std::string getClassName(lua_State* L);

    // ... more stuff...

};

 

class BaseClass_wrapper : public BaseClass, public luabind::wrap_base {

    // ... some stuff...

};

 

std::string BaseClass::getClassName(lua_State* L)

{

    BaseClass_wrapper* p = dynamic_cast<BaseClass_wrapper*>(this);

    std::string className("UNKNOWN");

    if (p != 0) {

        luabind::object myObject(L, p);

        luabind::class_info info = luabind::get_class_info(myObject); // no good!

        // no viable conversion from 'luabind::object' to 'const luabind::adl::argument'

        className = info.name;

    }

    return className;

}

 

 

Thanks for any suggestions,

Glen.

 

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Re: [luabind] How to get Lua class name from C++ class?

[Glen F. <hol...@gm...>]

Thanks, Christian, but I didn't manage to get anything to work in the way you describe.  I can't seem to simply substitute 'object' with 'argument'…  I also tried using myObject.push(L), then using the "from_stack" referenced argument to call get_class_info(), then doing a lua_pop(), but that just crashes on me (a bit later on)…and before that, it hasn't returned the correct class_info structure.  I think I'd need to see a simple example, sorry.

On the other hand, the "hacky" code from Eduard (see his earlier reply) does seem to work fine, as does another approach I came up with, where I just use luabind::call_function() to call the bound "class_info" function in Lua, then get the class_info structure by doing object_cast on the returned object.  Of course, this may be (?) a bit less efficient than doing the direct stack-fiddling you guys suggest, but it works.

Thanks,
Glen.

On Aug 28, 2013, at 4:07 PM, "Christian" <cn...@gm...> wrote:

> Just replace luabind::object with luabind::argument in your code. They work both the same, only that the first stores the referenced object in the registry, while the latter just leaves it on the stack.
>  
> If you ever have to convert one into another, just use the ones push() method and the others from_stack constructor (but avoid relative indices with luabind::argument).
>  
> From: Glen Fraser [mailto:hol...@gm...] 
> Sent: Wednesday, August 28, 2013 1:09 PM
> To: lua...@li...
> Subject: [luabind] How to get Lua class name from C++ class?
>  
> Hello there, I'm using luabind and trying to get the Lua subclass name from an instance of the base class in C++.
>  
> I want to use get_class_info(), but it expects an "argument" rather than an "object".  Perhaps there is a better way to do this, besides trying to figure out how to convert a luabind::object into a luabind::adl::argument…  Here is some example code that should illustrate the problem:
>  
> class BaseClass {
> public:
>     virtual ~BaseClass() {}
>     std::string getClassName(lua_State* L);
>     // ... more stuff...
> };
>  
> class BaseClass_wrapper : public BaseClass, public luabind::wrap_base {
>     // ... some stuff...
> };
>  
> std::string BaseClass::getClassName(lua_State* L)
> {
>     BaseClass_wrapper* p = dynamic_cast<BaseClass_wrapper*>(this);
>     std::string className("UNKNOWN");
>     if (p != 0) {
>         luabind::object myObject(L, p);
>         luabind::class_info info = luabind::get_class_info(myObject); // no good!
>         // no viable conversion from 'luabind::object' to 'const luabind::adl::argument'
>         className = info.name;
>     }
>     return className;
> }
>  
>  
> Thanks for any suggestions,
> Glen.
>  
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Re: [luabind] How to get Lua class name from C++ class?

[Christian <cn...@gm...>]

Just replace luabind::object with luabind::argument in your code. They work both the same, only that the first stores the referenced object in the registry, while the latter just leaves it on the stack.

 

If you ever have to convert one into another, just use the ones push() method and the others from_stack constructor (but avoid relative indices with luabind::argument).

 

From: Glen Fraser [mailto:hol...@gm...] 
Sent: Wednesday, August 28, 2013 1:09 PM
To: lua...@li...
Subject: [luabind] How to get Lua class name from C++ class?

 

Hello there, I'm using luabind and trying to get the Lua subclass name from an instance of the base class in C++.

 

I want to use get_class_info(), but it expects an "argument" rather than an "object".  Perhaps there is a better way to do this, besides trying to figure out how to convert a luabind::object into a luabind::adl::argument…  Here is some example code that should illustrate the problem:

 

class BaseClass {

public:

    virtual ~BaseClass() {}

    std::string getClassName(lua_State* L);

    // ... more stuff...

};

 

class BaseClass_wrapper : public BaseClass, public luabind::wrap_base {

    // ... some stuff...

};

 

std::string BaseClass::getClassName(lua_State* L)

{

    BaseClass_wrapper* p = dynamic_cast<BaseClass_wrapper*>(this);

    std::string className("UNKNOWN");

    if (p != 0) {

        luabind::object myObject(L, p);

        luabind::class_info info = luabind::get_class_info(myObject); // no good!

        // no viable conversion from 'luabind::object' to 'const luabind::adl::argument'

        className = info.name;

    }

    return className;

}

 

 

Thanks for any suggestions,

Glen.

 

Re: [luabind] How to get Lua class name from C++ class?

[eduard m. <mue...@go...>]

Hey,

you can
​ ​
use the "private" luabind::detail::object_rep*
luabind::detail::get_instance(lua_State* L, int index)
​here ​
instead.
This is quite a hack, but we at found no other "official" way on doing this
within a wrap_base:

​​
 std::string
​​
BaseClass::getClassName(lua_State* L)
 {
   luabind::detail::wrap_access::ref(*this).get(L);
   luabind::detail::object_rep* pObjectRep =
luabind::detail::get_instance(L, -1);
   ::lua_pop(L, 1); //ref.get

   if (pObjectRep)
   {
     return
​ ​
std::string (pObjectRep->crep()->name());
   }
   else
   {
     throw std::runtime_error(
       "Internal Error: failed to resolve a Lua wrapper class name");
   }
 }

Hope this helps.

Best regards,
Eduard


On Wed, Aug 28, 2013 at 1:09 PM, Glen Fraser <hol...@gm...> wrote:
>
> Hello there, I'm using luabind and trying to get the Lua subclass name
from an instance of the base class in C++.
>
> I want to use get_class_info(), but it expects an "argument" rather than
an "object".  Perhaps there is a better way to do this, besides trying to
figure out how to convert a luabind::object into a luabind::adl::argument…
 Here is some example code that should illustrate the problem:
>
> class BaseClass {
> public:
>     virtual ~BaseClass() {}
>     std::string getClassName(lua_State* L);
>     // ... more stuff...
> };
>
> class BaseClass_wrapper : public BaseClass, public luabind::wrap_base {
>     // ... some stuff...
> };
>
> std::string
> BaseClass::getClassName(lua_State* L)
> {
>     BaseClass_wrapper* p = dynamic_cast<BaseClass_wrapper*>(this);
>     std::string className("UNKNOWN");
>     if (p != 0) {
>         luabind::object myObject(L, p);
>         luabind::class_info info = luabind::get_class_info(myObject); //
no good!
>         // no viable conversion from 'luabind::object' to 'const
luabind::adl::argument'
>         className = info.name;
>     }
>     return className;
> }
>
>
> Thanks for any suggestions,
> Glen.
>
>
>
------------------------------------------------------------------------------
> Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more!
> Discover the easy way to master current and previous Microsoft
technologies
> and advance your career. Get an incredible 1,500+ hours of step-by-step
> tutorial videos with LearnDevNow. Subscribe today and save!
>
http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk
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> https://lists.sourceforge.net/lists/listinfo/luabind-user
>