Lua callback into module

Question

My script registers itself for a callback using

require "cmodule"
index = 1
cmodule.RegisterSoftButtonDownCallback(index, "callbackFunc")

where callbackFunc is the name (a string) of the callback function. Now I turned this script into a module, but the callback is not called anymore, I assume because the callback function is not in the scope of the cmodule. How can I solve this? (Lua newbie)

cmodule is a device driver that has Lua bindings.

Edit: My complete solution based in the answer from BMitch below:

require "cmodule"
local modname = "myModule"
local M = {}
_G[modname] = M
package.loaded[modname] = M
local cmodule = cmodule
local _G = _G
setfenv(1,M)

function callbackFunc()
    -- use module vars here
end
_G["myModule_callbackFunc"] = callbackFunc
index = 1
cmodule.RegisterSoftButtonDownCallback(index, "myModule_callbackFunc")

What is cmodule? That's not part of Lua 5.1. Where does it come from? Is it a global variable or a local one? — Nicol Bolas
– Nicol Bolas, Commented Jul 8, 2011 at 20:27
cmodule is a device driver that has Lua bindings. I do a require "cmodule" at the start of the script (loading cmodule.dll). It is not developed by me. If it is important to know what exactly it does I could try to contact the author. — Emile
– Emile, Commented Jul 9, 2011 at 9:35

BMitch · Accepted Answer · 2011-07-09 14:01:08Z

2

You need to have something defined in the global space for a string to be evaluated back to a function call.

Depending on how they implemented RegisterSoftButtonDownCallback, you may be stuck defining the function itself, rather than the table/field combination like myModule.callbackFunc. To minimize the namespace pollution, if you can't use myModule.callbackFunc, then I'd suggest myModule_callbackFunc=myModule.callbackFunc or something similar. So your code would look like:

require "cmodule"
index = 1
myModule_callbackFunc=myModule.callbackFunc
cmodule.RegisterSoftButtonDownCallback(index, "myModule_callbackFunc")

For a better fix, I would work with the cmodule developers to get their program to accept a function pointer rather than a string. Then your code would look like:

require "cmodule"
index = 1
cmodule.RegisterSoftButtonDownCallback(index, myModule.callbackFunc)

answered Jul 9, 2011 at 14:01

BMitch

271k52 gold badges555 silver badges512 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Emile Over a year ago

Thanks, this set me on the right track. I will add my solution to the original question so that others can benefit from it. If you think it can be improved upon then please comment.

Collectives™ on Stack Overflow

Lua callback into module

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related