How to iterate all content in a table using loops?
Please note:
I know how to iterate a table, this question is basically asking how to iterate ALL content in a table. For example, if you have a table like: local t = {a = 1, b = {1,2,3}} , I'd want to return a table with all it's unpacked data, assuming there are nested tables in it. Like getting all descendants of an object, except instead of iterating an object, it'd be a table.
Question
I know how I could iterate all content in a table with recursive functions, but is there a way to do it with loops instead? This is my current code for my current table iteration:
local function tree(t)
local all = {}
local function add(x)
for i,v in next, x do
all[#all+1] = v
if type(v) == "table" then
add(v)
end
end
end
add(t)
return all
end
for i,v in next, tree{
a = 1,
b = {1,2,3}
} do print(i,v) end -- prints all values
But I'd like a looped alternative a lot more. If anyone knows how or if this is possible, I'd appreciate the explanation. Thanks.
2 answers
To iterate through nested tables, you can used nested loops inside of nested functions.
local test = {1,2,3,a = {4,5,b = {6}}}
local function printall(tab)
for i,v in pairs(tab) do
if type(v) == "table" then --if v is a table then
printall(v) --run the function again on the value v
else
print(v)
end
end
end
printall(test)
additionally, you could use coroutines so that iterating through the nested tables wouldn't effect the rest of the code.
local test = {1,2,3,a = {4,5,b = {6}}}
local function printall(tab)
for i,v in pairs(tab) do
if type(v) == "table" then --if v is a table then
coroutine.resume(coroutine.create(printall),v) --run the function again on the value v under a new thread
else
print(v)
end
end
end
coroutine.resume(coroutine.create(printall),test)
EDITED
You could use a while loop:
local tab = {}
local num = 0
while num < #tab do
num = num + 1
if type(tab[num]) == "table" then
for _,v in pairs (tab[num]) do
print(v)
end
else
print(tab[num])
end
end
or a repeat loop:
local tab = {}
local num = 0
repeat
num = num + 1
if type(tab[num]) == "table" then
for _,v in pairs (tab[num]) do
print(v)
end
else
print(tab[num])
end
until
num == #tab
Both basically continue until num is equal to #tab.
type() is a function used to get the type of value you are putting into it's parameters.
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