Re: protecting exported data from within C
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- Subject: Re: protecting exported data from within C
- From: Romulo Bahiense <romulo@...>
- Date: 2005年3月15日 23:09:41 -0300
However, I find I can still modify the value of Account.version. I only
get the error message
if I try and add new fields to the table. From the description in the
book my function should
be called whenever lua tries to assign something to the table.
No. The __newindex metamethod will be called if, and only if, there are
no corresponding value in the respective table.
To avoid such behavior, you could create a table for the __index
metamethod which will hold read-only values, and create a function for
the __newindex metamethod that will check if the value already exists in
the __index table.
The __newindex function would be something like:
__newindex = function (obj,key,value)
local meta = getmetatable(obj)
if type(meta)~='table' or type(meta.__index)~='table' then
return
end
if rawget(meta.__index,key)~=nil then
error('Attempt to override "'..tostring(key).. '" - a constant value')
else
rawset(obj,key,value) -- Adds it to the table.
end
end
--rb