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debug.getupvalue

Summary

Returns the name and value of an upvalue

Prototype

name, value = debug.getupvalue (level, upvalue)


Description

Similar to debug.getlocal, returns the names and values of the upvalues for the nominated function. See also debug.setupvalue.


function newCounter ()
  local n = 0
  return function ()  -- anonymous function
    n = n + 1
    return n
    end -- function
end -- newCounter 

c = newCounter ()
c ()  -- count a couple of times
c ()

-- show upvalues in c

local i = 1

repeat
  name, val = debug.getupvalue (c, i)
  if name then
    print ("index", i, name, "=", val)
    i = i + 1
  end -- if
until not name

 -->
 
 index 1 n = 2


In this example the function c is a closure (with associated upvalue "n").

NOTE: Lua does not let you see or change upvalues for C functions (eg. string.gfind).


See Also ...

Lua functions

debug.debug - Enters interactive debugging
debug.getfenv - Returns the environment of an object
debug.gethook - Returns the current hook settings
debug.getinfo - Returns a table with information about a function
debug.getlocal - Returns name and value of a local variable
debug.getmetatable - Returns the metatable of the given object
debug.getregistry - Returns the registry table
debug.setfenv - Sets the environment of an object
debug.sethook - Sets a debug hook function
debug.setlocal - Sets the value of the local variable
debug.setmetatable - Sets the metatable for an object
debug.setupvalue - Sets an upvalue for a function
debug.traceback - Returns a string with a traceback of the stack call

Topics

Lua base functions
Lua bc (big number) functions
Lua bit manipulation functions
Lua coroutine functions
Lua debug functions
Lua io functions
Lua math functions
Lua os functions
Lua package functions
Lua PCRE regular expression functions
Lua script extensions
Lua string functions
Lua syntax
Lua table functions
Lua utilities
Scripting
Scripting callbacks - plugins

(Help topic: lua=debug.getupvalue)

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