Re: [LUA]: Cannot use userdata as table index
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- Subject: Re: [LUA]: Cannot use userdata as table index
- From: Tom N Harris <whoopdedo@...>
- Date: 2015年7月10日 12:45:10 -0400
On Saturday, July 11, 2015 02:23:14 AM Борис Александров wrote:
> http://prntscr.com/7r4ecw It seems to me that lua compares table index and
> given value by address, not by _equal metamethod
>
This is correct. Only the primitive
Since the GetPlayer objects define a __tostring metamethod, you can convert the
userdata to string for use as a table key.
The __equals metamethod wouldn't be useful for tables. Lua would need a __hash
metamethod that returns a value suitable as a table key. But I wonder what
strange things could happen if A==B is not the same as hash(A)==hash(B)?
And anyway you can roll your own table with meta-keys.
function objecthash(o)
-- exercise for the reader: memoize keys for the lifetime of the object
local mt = getmetatable(o)
if mt and mt.__hash then
return mt.__hash(o)
end
return o
end
__index = function(t,o)
return getmetatable(t).__proxy[objecthash(o)]
end
__newindex = function(t,o,v)
getmetatable(t).__proxy[objecthash(o)] = v
end
--
tom <telliamed@whoopdedo.org>