How to iterate through table in Lua?

So, I have a table something along these lines:

arr =
{
apples = { 'a', "red", 5 },
oranges = { 'o', "orange", 12 },
pears = { 'p', "green", 7 }
}

It doesn't seem like it's possible to access them based on their index, and the values themselves are tables, so I just made the first value of the nested table the index of it, so it now looks like this:

arr =
{
apples = { 0, 'a', "red", 5 },
oranges = { 1, 'o', "orange", 12 },
pears = { 2, 'p', "green", 7 }
}

So, now any time I use one of these tables, I know what the index is, but still can't get to the table using the index, so I started to write a function that loops through them all, and check the indexes until it finds the right one. Then I realized... how can I loop through them if I can't already refer to them by their index? So, now I'm stuck. I really want to be able to type arr.apples vs arr[1] most of the time, but of course it's necessary to do both at times.

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If you want to refer to a nested table by multiple keys you can just assign them to separate keys. The tables are not duplicated, and still reference the same values.

arr = {}
apples = {'a', "red", 5 }
arr.apples = apples
arr[1] = apples

This code block lets you iterate through all the key-value pairs in a table (http://lua-users.org/wiki/TablesTutorial):

for k,v in pairs(t) do
print(k,v)
end
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最佳答案

To iterate over all the key-value pairs in a table you can use pairs:

for k, v in pairs(arr) do
print(k, v[1], v[2], v[3])
end

outputs:

pears   2   p   green
apples  0   a   red
oranges 1   o   orange

Edit: Note that Lua doesn't guarantee any iteration order for the associative part of the table. If you want to access the items in a specific order, retrieve the keys from arr and sort it. Then access arr through the sorted keys:

local ordered_keys = {}


for k in pairs(arr) do
table.insert(ordered_keys, k)
end


table.sort(ordered_keys)
for i = 1, #ordered_keys do
local k, v = ordered_keys[i], arr[ ordered_keys[i] ]
print(k, v[1], v[2], v[3])
end

outputs:

  apples  a   red     5
oranges o   orange  12
pears   p   green   7
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All the answers here suggest to use ipairs but beware, it does not work all the time.

t = {[2] = 44, [4]=77, [6]=88}


--This for loop prints the table
for key,value in next,t,nil do
print(key,value)
end


--This one does not print the table
for key,value in ipairs(t) do
print(key,value)
end
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For those wondering why ipairs doesn't print all the values of the table all the time, here's why (I would comment this, but I don't have enough good boy points).

The function ipairs only works on tables which have an element with the key 1. If there is an element with the key 1, ipairs will try to go as far as it can in a sequential order, 1 -> 2 -> 3 -> 4 etc until it cant find an element with a key that is the next in the sequence. The order of the elements does not matter.

Tables that do not meet those requirements will not work with ipairs, use pairs instead.

Examples:

ipairsCompatable = {"AAA", "BBB", "CCC"}
ipairsCompatable2 = {[1] = "DDD", [2] = "EEE", [3] = "FFF"}
ipairsCompatable3 = {[3] = "work", [2] = "does", [1] = "this"}


notIpairsCompatable = {[2] = "this", [3] = "does", [4] = "not"}
notIpairsCompatable2 = {[2] = "this", [5] = "doesn't", [24] = "either"}

ipairs will go as far as it can with it's iterations but won't iterate over any other element in the table. 

kindofIpairsCompatable = {[2] = 2, ["cool"] = "bro", [1] = 1, [3] = 3, [5] = 5 }

When printing these tables, these are the outputs. I've also included pairs outputs for comparison.

ipairs + ipairsCompatable
1       AAA
2       BBB
3       CCC


ipairs + ipairsCompatable2
1       DDD
2       EEE
3       FFF


ipairs + ipairsCompatable3
1       this
2       does
3       work


ipairs + notIpairsCompatable


pairs + notIpairsCompatable
2       this
3       does
4       not


ipairs + notIpairsCompatable2


pairs + notIpairsCompatable2
2       this
5       doesnt
24      either


ipairs + kindofIpairsCompatable
1       1
2       2
3       3


pairs + kindofIpairsCompatable
1       1
2       2
3       3
5       5
cool    bro
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Hi guys i am new in LUA but these answers helped me only like an half.So i write my own.

for i in pairs(actions) do
if actions[i][3] ~= nill then
--do something
end
end
  1. i - is index of value in table similar like in c#
  2. actions - just name of table
  3. actions[i][3] it will check all indexes in table if their 3rd value is not nil

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