Do the same thing for 4 conditions else do something else

Question

I have a system that I need translate to Lua. The code is to read an XML file.

cat = elementAttributeTable["Category"] -- This will be 3 char code.

Now, if cat is e.g. "MUS" or "MUA" or "XMS", I need to process other elementAttributeTable[] information. Else do some default stuff.

I have seen some info using a Table, but can't find an if in_table() thing. Other languages have the Select...Case, that I don't see in Lua.

How could I do this?

Answer 1

One straightforward way to express this is using or:

if cat == "MUS" or cat == "MUA" or cat == "XMS" then
    -- process information
else
    -- default behavior
end

given the few values you are testing for, this is completely fine.

You might want to write yourself a helper:

local function equals_any(value, ...)
    local n = select("#", ...)
    for i = 1, n do
        if value == select(i, ...) then
            return true
        end
    end
    return false
end

Usage: if equals_any(cat, "MUS", "MUA", "XMS") then ... end.

Alternatively, if you want a more "data-driven" approach or have many more categories to check for (such that it negatively affects performance), you could use a table:

local categories = {MUS = true, MUA = true, XMS = true}
if categories[cat] then
    -- process information
else
    -- default behavior
end