Lua string concatenation within table constructor

Question

I'm trying to initialize a table of default properties for my script, and I'm facing the following scenario:

_property_table = {

    k1 = "val1",
    k2 = "val2",
    k3 = k1 .. "val3",

}

print(_property_table.k3)

When trying to concatenate k1 within the table constructor, lua fails with the following error:

_impl error: [string "main.lua"]:10: attempt to concatenate global 'k1' (a nil value)

Is this behavior expected, or am I missing something?

I'm fairly new to Lua, so any tips or suggestions on how to proceed would be appreciated.

Thanks

Answer 1

That behaviour is expected: k1 is not a variable name, k1 = is simply a shortcut for ["k1"] = inside a table expression. There are two basic solutions:

1. Use a variable:

   local k1 = "val1"
   _property_table = {
       k1 = k1,
       k2 = "val2",
       k3 = k1 .. "val3",
   }
   

2. Assign k3 after the table creation:

   _property_table = {
       k1 = "val1,
       k2 = "val2",
   }
   _property_table.k3 = _property_table.k1 .. "val3"