CODEWITHSUNDEEP
lua
user441521
user441521

Reputation: 6998

lua's loadstring() not working with tables

I have some text and I'm trying to load it via load string. The following works:

local m = loadstring("data = 5")()

But when the data is a table it doesn't work and gives the error "attempt to call a nil"

local m = loadstring("data = { 1 = 10}")()

Upvotes: 0

Views: 1429

Answers (2)

Nick Gammon
Nick Gammon

Reputation: 1171

If you had added an assert you would have got a more helpful message:

local m = assert (loadstring("data = { 1 = 10}"))()

Result:

stdin:1: [string "data = { 1 = 10}"]:1: '}' expected near '='
stack traceback:
    [C]: in function 'assert'
    stdin:1: in main chunk
    [C]: ?

And to actually answer the question, unless the table key happens to follow Lua variable naming rules, you have to put it inside square brackets, eg.

local m = assert (loadstring("data = { [1] = 10}"))()

m is still nil when I do this

What does that matter? The loadstring is done.

Just do this:

assert (loadstring("data = { 1 = 10}"))()
print (data [1])

You don't need the variable m. The loadstring puts a table into data - that is the important thing.

Upvotes: -1

hjpotter92
hjpotter92

Reputation: 80649

The table declaration in lua require integer keys to be put inside square brackets:

data = {
  [1] = value,
}

The enclosing of keys in square brackets is always allowed, valid and possible. It can be skipped iff your key follows the pattern: [A-Za-z_][A-Za-z0-9_]* (which is the same as a valid variable name in lua)

Upvotes: 2

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