Catch get/set of userdata in table?
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- Subject: Catch get/set of userdata in table?
- From: "J. Perkins" <jason@...>
- Date: 2001年9月06日 17:33:47 -0400
Is there a way to catch a get/set to a userdata object that is stored in
a table? I know how to do it for a global variable, like LHF showed a
while back (see example below) -- is there some way to do an equivalent
operation on a table member?
I have a C++/Lua component system, and rather than mirroring all of the
get...() and set...() calls of C++ I'd like to make them look like
regular table variables and have assignments transparently call the C++
get...() and set...() methods under the hood. So if I had something like
this in C++:
struct MyComponent {
int getValue();
void setValue (int value);
};
In Lua it would look like:
MyComponent.value = 22;
x = MyComponent.value
I got it working by *not* putting anything in the table, catching the
"gettable" and "settable" calls and manually looking up the proper table
method from an internal array of entry points. It's ugly. Is there a
more elegant way to make this happen?
Thanks,
Jason
From: Luiz Henrique de Figueiredo <lhf@t...>
Date: Wed May 10, 2000 5:54 pm
Subject: RE: Direct accessing of application variables from lua
extern int I,J;
static void getTint(void)
{
int* var=(int*) lua_getuserdata(lua_getparam(2));
lua_pushnumber(*var);
}
static void setTint(void)
{
int* var=(int*) lua_getuserdata(lua_getparam(2));
int val=(int) lua_getnumber(lua_getparam(3));
*var=val;
}
void export(void)
{
int Tint=lua_newtag();
lua_pushusertag(&I,Tint); lua_setglobal("I");
lua_pushusertag(&J,Tint); lua_setglobal("J");
lua_pushcfunction(getTint); lua_settagmethod(Tint,"getglobal");
lua_pushcfunction(setTint); lua_settagmethod(Tint,"setglobal");
}