Lua - check if array exists

Question

I'm trying to find out if a certain array exists via an if statement such as

if array{} == nil then array = {} else print("it exists") end

The above doesn't work it seems and I have no way of checking if it exists, basically I'm creating an AddOn which scans a log for a certain event and if it's true it returns the spellName. I wish to create an array with that spellName, however spellName = {} doesn't work as it seems to just create a new array (rather than updating the existing one).

local _SPD = CreateFrame("Frame");
_SPD:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED");
_SPD:SetScript("OnEvent", function(self, event, ...)

local timestamp, type, sourceName = select(1, ...), select(2, ...), select(5, ...)

if (event == "COMBAT_LOG_EVENT_UNFILTERED") then
    if select(2,...) == "SPELL_AURA_APPLIED" then
        if select(5,...) == UnitName("player") then

            local spellID, spellName = select(12, ...), select(13, ...)

             spellName = { 
                sourceName = {

                } 
            }

            table.insert(spellName["sourceName"], {id = spellID, stamp = timestamp })

            for k,v in pairs ( spellName["sourceName"] ) do
                print (k.. ": " ..v["id"].. " at " ..v["stamp"])
            end 
        end
    end
end
end);

Basically it's just re-creating the table every time a certain aura is applied on me (which is expected behavior)

I've banged my head but I have no idea how to check if spellName (and sourceName) exists and if so do not create them again since in this case the variable already exists because it returns the value to me so I can't check if they're nil as they won't be, I need to somehow check if a table exists on those values and if not create them.

Thanks in advance.

local spellID, spellName = select(12, ...), select(13, ...) is silly. Get rid of the , select(13, ...) and just leave the select(12, ...). select() actually returns all values, starting with the given index, not just a single value, so saying local a, b = select(12, ...) will assign the 12th arg to a and the 13th arg to b. — Lily Ballard
– Lily Ballard, Commented Jan 30, 2013 at 22:46

hjpotter92 · Accepted Answer · 2013-01-30 22:40:38Z

2

Your declaration for table checking is wrong. Use it like this:

if type(array) == "table" then
  print("it exists")
else
  array = {}
end

edited Jan 30, 2013 at 22:40

answered Jan 30, 2013 at 19:14

hjpotter92

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8 Comments

furq Over a year ago

For what it's worth, this could be written as array = type(array) == "table" and array or {}.

Mud Over a year ago

You could have just written if type(array) == 'table' then -- which will return nil if array is nil, making the first test unnecessary.

hjpotter92 Over a year ago

@Mud hmm, I didn't know that type can take nil arguments. Edited.

sof2er Over a year ago

Thanks for the help, I've added the following lines:

print(spellName)     if type(array) == spellName then     print("it exists")     else     spellName = {}     print(spellName)     print("created")     end

and it seems to return the first print with the spellName but the one after the creation of the table returns with a table number (which is different everytime I run the spell while the first print stays the same.

hjpotter92 Over a year ago

You need to use if type(spellName) == "table" as your if condition.

|

Egor Skriptunoff · Accepted Answer · 2013-01-31 04:06:09Z

1

Try this:

local spellID, spellName = select(12, ...), select(13, ...)
spellName = spellName or {}
spellName.sourceName = spellName.sourceName or {}
table.insert(spellName.sourceName, {id = spellID, stamp = timestamp })

edited Jan 31, 2013 at 4:06

answered Jan 30, 2013 at 19:42

Egor Skriptunoff

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3 Comments

sof2er Over a year ago

Doesn't work unfortunately, returned an error

Locals: (*temporary) = nil (*temporary) = <table> {  id = 52127  stamp = 1359598562.074 } (*temporary) = "table expected, got nil"

Egor Skriptunoff Over a year ago

@user2026598 - Edited my answer. Try again please.

sof2er Over a year ago

didn't seem to work either, however adding myTable = {} at the top and using if myTable[spellName] then print("exists") else myTable[spellName] = {} end seemed to do the trick. Thanks to the following people in this thread: mmo-champion.com/threads/…

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