Requesting assistance coercing a string to a function call

[captn_retardo]

Hello all,
I am attempting to load a string from a file, and then coercing that string into the function name. For example, I would like to do something like:

Code: Select all

function test_func()
    print("yes!")
end

str = "test_func"

str()

So that end part, where I str() is obviously wrong, as a string is not a function. I am at a loss at how to do this. Does anyone have any tricks they can share?

[Robin]

Try using loadstring:

Code: Select all

function test_func()
    print("yes!")
end

str = "test_func"

assert(loadstring(str))()

Disclaimer: I didn't test it.

[bartbes]

Try this:

Code: Select all

function test_func()
    print("yes!")
end

str = loadstring("test_func()") --notice the (), better syntax..

str()

--or..
str = "test_func()"
loadstring(str)() --however, this converts to a function every time

Robin beat me, but I hope this is going to help anyway

EDIT: though robin's suggestion of using assert is good..

[Robin]

We both were almost right. I think this is the way to go:

Code: Select all

function test_func()
    print("yes!")
end

str = assert(loadstring("test_func()"))

str()

Explanation:
"test_func()" is the string that gets executed.
loadstring creates a function (or was it called "chunk" or something like that?), containing the code from a string
assert gives an error if something went wrong, otherwise passes the function to str

[bartbes]

So.. what I said (if you include my edit)..

I kind of feel like saying "I was better", but I won't.. or will I?

[Robin]

I kind of feel like saying "I was better", but I won't.. or will I?

I say we call it a draw

[captn_retardo]

Thank you so much for the quick response. Loadstring() is exactly what I was looking for.

[Jake]

Rather than loading the string as a piece of Lua you can just call the function from the global table

Code: Select all

local str = "test_func"
_G[str]()

I would prefer to do that because it seems safer to me.

[bartbes]

And what if you want to do more than just calling a single functions without arguments?

[Jake]

Depends on exactly what but surely it's quicker just to do a table lookup, right?