Why isn't my iteration for the table not printing anything?
I've made an example of what I'm trying to convey and I don't know why it's not working as expected.
local tab = {["key"] = nil}
for k, v in pairs(tab) do
print(v)
end
What I expect it to do is print nil since the value of the key is nil, but what it's doing is print completely nothing at all. However, if I do set the value to something else other than nil, it functions as expected and prints the value.
local tab = {["key"] = "hi"}
for k, v in pairs(tab) do
print(v)
end
-- prints "hi"
Directly printing the value from the table like tab.key seems to print nil so why doesn't iterating through the table not work?
2 answers
Hello!
I tried out a few variations myself just to be sure.
Here's the code:
local Table1 = {["Key"] = nil}
local Table2 = {["Key"] = "nil"}
local Table3 = {["Key"] = "Hi1"}
local Table4 = {["Key1"] = "Hi2",
["Key2"] = nil,
["Key3"] = 256
}
local function PrintTable(Table)
for i, v in pairs(Table) do
print(v)
end
end
Table4.Key3 = Table4.Key2
PrintTable(Table1)
PrintTable(Table2)
PrintTable(Table3)
PrintTable(Table4)
print(Table1.Key, Table2.Key, Table3.Key, Table4.Key1, Table4.Key2, Table4.Key3)
The result printed was: nil Hi1 Hi2 nil nil Hi1 Hi2 nil nil
So to answer your question, when you iterate over a table (Such as with the for i, v in pairs) it simply skips the nil value. When you Deliberately call it however then it'll print the result.
Basically, it's a resource saving measure. It still works as expected though.
Hi noposts,
I think the answer to your question is simple. When you iterate through a table, it ignores all values that are nil.
You can see this when you try it with a normal table and not a dictionary
local tab = {nil, nil, "hi"}
for _, val in next, tab do
print(val); -- Only runs once printing "hi".
end
So, a table ignores all values that are nil, since an empty table has nil values inside of it to begin with. Also, you asking it to print the value by doing:
tab = {["key"] = nil};
print(tab.key);
This doesn't mean anything because if you were to do tab.[any word] it will just print nil. So, tab.whatever or tab.nothing or tab.anyword will end up printing nil, since those don't exist in the first place. So, ["key"] isn't even recognized as a real value. It just ignores that whole value since it's nil.
Well, I hope I explained the issue well and helped. Have a wonderful day/night.
Thanks,
Best regards,
~~ KingLoneCat