local mooDB

local defaults = {
    a = {
        foo = "bar"
    },
    b = 1,
    c = {
        bar = "foo"
    },
}

if not mooDB then
    -- NOTE: This would not be in the actual real world code.  This
    -- simulates user data, normally loaded from some sort
    -- of datastore, which is SavedVariables in the case of
    -- World of Warcraft.
    mooDB = {
        c = {
            bop = "whee"
        }
    }
end

function inheritdefaults(t, defaults)
    for k,v in pairs(defaults) do
        if t[k] then
            if type(v) == "table" then
                inheritdefaults(t[k], v)
            end
        end
    end

    local mt = getmetatable(t) or {}
    function mt:__index(k)
        return defaults[k]
    end
    return setmetatable(t, mt)
end

inheritdefaults(mooDB, defaults)

assert(mooDB ~= defaults)
assert(mooDB.a == defaults.a)
assert(mooDB.c ~= defaults.c)
assert(mooDB.a.foo == "bar")
assert(mooDB.b == 1)
assert(mooDB.c.bar == "foo")
assert(mooDB.c.bop == "whee")

Lua: Sane Granular Defaults for User Supplied Data

Other