Using multiple Lua scripts with c++

Question

I'm trying to use lua with my c++ program and when I look up for how to use multiple lua script with I found this result https://stackoverflow.com/a/61684333/22979136
I modified this result and eventualy end up with this

local file_env = {}
local file_chunk = {}

function AddScript(ScriptLocation, index, Nd)
    file_env[index] = setmetatable({}, {__index = _G})
    file_chunk[index] = loadfile(ScriptLocation)

    _ENV = file_env[index]

    file_chunk[index]()

    file_env[index].InitNode(Nd)
    file_env[index].Start()
end

function UpdateScript(index)
    print(file_env[index])
    file_env[index].Update()
end

but there is some issue
when I call the "UpdateScript" function in my c++ program I get no result and "print(file_env[index])" just gives me the "nill" result
how can I fix this?

I tried to call the "UpdateScript" function inside the "AddScript" function but that didnt seem to help

Can you please provide a minimal example of how you call these functions from C++ which results in this error? — YurkoFlisk
– YurkoFlisk, Commented Nov 24, 2023 at 21:17

ESkri · Accepted Answer · 2023-11-27 02:43:30Z

1

In Lua, an environment is an internal property of a function.
So, replace

    file_chunk[index] = loadfile(ScriptLocation)

    _ENV = file_env[index]

with

    file_chunk[index] = loadfile(ScriptLocation, "t", file_env[index])

to embed environment into a function on its creation.
You will be unable to set this function's environment later.

edited Nov 27, 2023 at 2:43

answered Nov 24, 2023 at 19:08

ESkri

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5 Comments

Codyea Over a year ago

when i tried this and run the update function on my program the results were the same i think my problem is that this function does not set the tables in the script it only changes the value in the function and i dont know how to fix this

Joseph Sible-Reinstate Monica Over a year ago

"You will be unable to set this function's environment later." You can, with the debug library: Recreating setfenv() in Lua 5.2

ESkri Over a year ago

@JosephSible - Debug library is not helpful here. That solution doesn't work if Lua program is compiled to bytecode with debug info stripped (because upvalue names are stripped too, and you never know which one is the "_ENV")

Joseph Sible-Reinstate Monica Over a year ago

@ESkri Don't chunks always only have one upvalue?

ESkri Over a year ago

@JosephSible - Yes.

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