Lua weak reference

Question

I'm aware of the weak tables functionality in Lua, however I would like to have a weak reference with a single variable.

I've seen this proposal which suggests an API as follows:

-- creation
ref = weakref(obj)
-- dereference
obj = ref()

which would seem ideal. However this doesn't appear to be in the documentation elsewhere; only weak tables.

Is there something analogous to Python's weak reference to object functionality?

Answer 1

Something like this can do what you want I believe:

local obj = {value = "obj.value"}

local ref = setmetatable({real = obj}, {__mode = "v", __call = function(self) return self.real end})

print(obj.value)
print(ref.real.value)
print(ref().value)

obj = nil
collectgarbage()
collectgarbage()

print(obj)
print(ref.real)
print(ref())

The __call part is optional but gives you the ref() call syntax. Without it you have to use the direct access version.