I'm trying to figure out how to "lock" a value in a table. Basically like:
local t = {
x = 1;
}
-- So if someone tried to change "x", it would be set back to default
t.x = 2
So, if someone tried to change a key (or the key's value) in a table, that already exists, how would i go about doing that? The __index and __newindex metamethods only work when the key doesn't exist, so is there any way i could make the script catch changes to existing data in a table?
unprotected = {
a = 1,
b = 2,
c = 3
}
protected = {
d = 4,
e = 5,
f = 6
}
--Anything that's already in the table will be unprotected.
t = setmetatable(unprotected, {
__metatable = "The metatable is locked", --Lock it up
__index = protected, --If it's not in the table, it's a key protected by __newindex.
__newindex = function(self, key, value)
if protected[key] then
error("Key '"..key.."' is protected in this table.")
else
rawset(self, key, value)
end
end
})
t.a = 5
print(t.a)
t.d = 5
print(t.d)
--You might find this useful in a module or in _G. You might not.
--return t
--_G.t = t
Why is this downvoted?
Not sure, but I'll sure accept this answer. Thanks for the example funyun.
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1 comment
I would have thought that the __index metamethod catches changes in the value? Because it will usually cause a c-stack overflow when you try to change it without rawset inside the metamethod.