Lua type function for nested table reference

Question

I'm just starting to write Lua code for World of Warcraft. I frequently need to check to see if a global variable nested in a table has been defined by another author's Lua code.
Example:

Mytable[MyfirstLvl].Mysecondlvl.fred where the variable MyfirstLvl1 has spaces in it

At present I'm using:

if (type(Mytable) == 'table') and (type(Mytable[MyfirstLvl]) == 'table') and (type(Mytable[MyfirstLvl].Mysecondlvl) == 'table') then
    --some code using Mytable[MyfirstLvl].Mysecondlvl.fred
end

I'd like an easier way to do this. I thought of writing a function that uses _G, but can't find any examples of parsing dynamic variable names that have '[' and ']' in them.

Is there an easy way to tell if a value nested several levels down in a table has been defined or can someone help with creating a custom function to do this?

Here is what I came up with:

function newType(reference)
    if type(reference) ~= 'string' then
        print('...argument to Type must be a string')
        return
    end

    local t = {string.split('].[', reference)}

    local tt = {}
    for k, v in ipairs(t) do
        if string.len(v) ~= 0 then
            local valueToInsert = v
            if (string.sub(v, 1, 1) == '"') or (string.sub(v, 1, 1) == "'") then
                valueToInsert = string.sub(v, 2, -2)
            elseif tonumber(v) then
                valueToInsert = tonumber(v)
            end
            table.insert(tt, valueToInsert)
        end
    end

    local myReference = _G
    local myType
    for i, curArg in ipairs(tt) do
        if type(myReference) ~= 'table' then            
            return 'nil'            
        end
        if type(myReference[curArg]) ~= 'nil' then
            myReference = myReference[curArg]
            myType = type(myReference)
        else
            return 'nil'
        end
    end
    return myType

end    
SavedDB = {}
SavedDB.profiles = {}
SavedDB.profiles.Character = {}
SavedDB.profiles.Character.name = 'fireymerlin'
print(newType('SavedDB.profiles["Character"].name')

All of your comments helped me think this through. Thank you. If you see a better way to accomplish this (I hope the example at the bottom helps), please let me know. I was trying to make a function that I could pass one string to, but couldn't get the pattern matching to work when the string included ["Character"].

Answer 1

Would that work for you?

if type( ((Mytable or {})[MyfirstLvl] or {}).Mysecondlvl ) == "table"