light userdata (was: Lua 5 and tags)
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- Subject: light userdata (was: Lua 5 and tags)
- From: Wim Couwenberg <debosberg@...>
- Date: 2004年7月25日 04:13:07 -0700 (PDT)
> If not, how can we use them since there are
> absolutely no way we could test the type of
> these light userdata without metatable nor tag.
I tend to use light userdata in the following
situations:
1) As key for the registry. This is a very convenient
way to make sure your registry keys are private. An
example:
instead of:
/* retrieve private data */
lua_pushstring(L, "mykey");
lua_gettable(L, LUA_REGISTRYINDEX);
I do it like this:
/* in file scope: */
static char mykey[] = "mykey";
/* retrieve private data */
lua_pushlightuserdata(L, mykey);
lua_gettable(L, LUA_REGISTRYINDEX);
2) If garbage collection is not an issue you can
implement types purely in scripts and add the actual
C/C++ object as light userdata, e.g. by assigning it
to a "__data" key or such. This can save some hassle
to create, administrate and access user data.
--
Wim
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