Introduction
Hello I am dand, a 2 year lua programmer and this is just a small guide to hopefully explain next to beginners and people who don’t even know it existed.
next is a builtin function used to give functionality to pairs (not ipairs) and allows us to loop through dictionaries easily.
Simple terms
next returns the a tuple of the next index and value in the given dictionary. The first arguement is the given dictionary, and the second arguement is the current index. To get the first index you set the second parameter to nil
Example
Heres an example in code
local dict = {
['Greeting'] = 'Hello!'
['Farewell'] = 'Bye!'
}
local i, v = next(dict) -- 'Greeting', 'Hello!'
next(dict, i) -- 'Farewell', 'Bye!'
What does this mean?
Well this allows for use to loop through dictionaries and this is what pairs does!
pairs described as a function:
local function pairs(t)
return next, t, nil
end
This may be confusing, and tbh for anyone who isn’t a magician at lua, it is. It might take you a while to understand by what a for loop does when given a function, is keep running that function and uses the returned value as the second parameter to run again.
local function for(func, t, f)
while true do
local i, v = func(t, i)
if i and v then
f(i, v)
else
break
end
end
end
local t = {
['Hello'] = 'hi'
}
for(next, t, function(i, v)
print(i, v)
end)
This is just a custom for loop in function form as an example.
What about ipairs?
Well ipairs is just simple. It just keeps adding up the index until the value becomes nil.
local function iterate(t, i)
i += 1
local v = t[i]
if v then
return i,v
end
end
local function ipairs(t)
return iterate, t, 0
end
Conclusion
This is just a small guide and requires a good knowledges of lua to understand. Feel free to read these sources for more information and ask questions if you’re confused.