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

Jasmijn · Accepted Answer · 2020-05-10 13:58:08Z

2

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:

Use a variable:

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

Assign k3 after the table creation:

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

answered May 10, 2020 at 13:58

Jasmijn

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1 Comment

Jolisif693 Over a year ago

Thank you, I went on and followed the second approach you described.

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