gistfile1.lua

-- Note: Lua Proxy Userdata is what holds the reference to the obj-c object

function dummyCode(array) -- array is an instance of an obj-c NSArray Object
   local thing = NSObject:alloc():init() -- Assume the Lua Proxy Userdata for 'thing' is 
                                         -- automatically put into the strong set

   ... -- Misc Lua code. Assume the Lua garbage collector will be run during this code. Since
       -- 'thing' is not being retained by any other obj-c code (its retain count is 1) it is 
       -- removed from the strong set.

   array:insertObject(thing) -- Now 'thing' has been retained by obj-c (its retain count is 2), 
                             -- but Lua has no way of knowing it should be added back into the
                             -- strong set.

   thing = nil -- Now the Lua Proxy Userdata will be destroyed on the next garbage collection, 
               -- yet the 'thing' obj-c object is still being used and will need the Lua Proxy
               -- Userdata 
end