I know I can't directly get a dictionary table length in Lua... but can I know at least if it has any entry or not?

Question

As summary states... Lets say I want to quickly know if a table is empty or has been filled with some hash entries, is there a simpler and generic (I mean, not having to resort to check if certain entry exists) way than having to parse the table to simply know this? Thanks.

Answer 1

Yes, you can use the next function to do this. If the table t is empty, then next(t) will return nil. Otherwise, next(t) will return the first index and the associated value.

local t1 = {}
local index1, value1 = next(t1)
print(index1, value1) -- nil    nil

local t2 = {a = "b", c = "d"}
local index2, value2 = next(t2)
print(index2, value2) -- c  d

Note that the order that next(t) accesses the table in is arbitrary. In the case of t2, it happened to choose index "c" first.