passing pointers using LuaBridge
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- Subject: passing pointers using LuaBridge
- From: Moose <moose@...>
- Date: 2014年4月07日 09:38:39 +0200
Hi all,
I am making moderate progress integrating Lua into my C++ environment.
After trying many different ways of wrapping C or C++ code I ended up
with two candidates that seemed to suit my needs best. LuaBridge
(https://github.com/vinniefalco/LuaBridge) and LuaWrapper
(https://bitbucket.org/alexames/luawrapper).
I was able to create C++ wrappers for existing classes with both, and,
inside my scripts, to create objects of those types and call methods
upon them. So far so good. However, with both implementations I have
failed to pass existing objects with C++ lifetime into the script.
With LuaBridge for example I do this (simplified):
int luaopen_mylib_1(lua_State *L) {
using namespace luabridge;
getGlobalNamespace(L)
.beginNamespace("mylib")
.addFunction ("testfree", testfree)
.beginClass<MyClass>("MyClass")
.addFunction("foo", &MyClass::foo )
.endClass()
.endNamespace();
// quite like this interface btw.
return 0;
}
... then ...
using namespace luabridge;
lua_State *L = luaL_newstate();
luaL_openlibs(L);
// and register the functions within that context
luaopen_mylib_1(L);
// create MyClass instance
MyClass *p = new MyClass();
setGlobal(L, p, "mc"); // a LuaBridge Method that pushes the
pointer as
// global userdata on the
stack
if (luaL_dofile(L, "luawrapper_reuse.lua")) {
std::cerr << "Lua program returned an error: \n";
std::cerr << lua_tostring(L, -1);
std::cerr << std::endl;
lua_close(L);
}
delete p;
All very straight forward.
Then in my script...
[[
print("Executing LuaBridge test")
mylib.testfree()
mc:foo()
]]
The method testfree() is being called all right. At least I see the
output. But then, when I try to access the instance "mc", I get:
luawrapper_reuse.lua:6: attempt to index global 'mc' (a userdata value)
Despite the fact that I do everything by the book, exactly the way it
is described in LuaBridges manual. Can anyone tell me what I do wrong?
How can I access the object?
It seems like Lua does know it. A pointer by the name 'mc' has been
pushed as userdata into the context, which is how I understand this is
supposed to work. But why can I not de-reference it and call a method?
So close to the goal and yet all my efforts fail on this....
With that Test I use LuaJit 2.0 on Windows64 (MSVC9).
Help is much appreciated.
Thanks,
Moose.