Re: [LUA]: Cannot use userdata as table index

[Tom N Harris <whoopdedo@...>]

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>