Store a Lua function?

Question

Calling a Lua function from C is fairly straight forward but is there a way to store a Lua function somewhere for later use? I want to store user defined Lua functions passed to my C function for use on events, similar to how the Connect function works in wxLua.

Answer 1

check the registry (luaL_ref()). it manages a simple table that lets you store any Lua value (like the function), and refer to it from C by a simple integer.

Answer 2

Building on Javier's answer, Lua has a special universally-accessible table called the registry, accessible through the C API using the pseudo-index LUA_REGISTRYINDEX. You can use the luaL_ref function to store any Lua value you like in the registry (including Lua functions) and receive back an integer that can be used to refer to it from C:

// Assumes that the function you want to store is on the top of stack L
int function_index = luaL_ref(L, LUA_REGISTRYINDEX);

Answer 3

The easiest way to do this is for your function to take a "name" and the lua function text. Then you create a table in the interpreter (if it doesn't exist) and then store the function in the table using the named parameter.

In your app just keep hold of a list of function names tied to each event. When the event fires just call all the functions from your table whose key matches the names in the list.