Issue with variable scope

[Nimhfree]

Hi, I have a problem that someone can probably explain to me pretty easily, but my head is a little fuzzy at the moment from lack of sleep.

In the following code I have a variable followerName declared outside of the for loop. I insert a new table into t with a function f defined to pass in followerName to the call to SetMapAreaQuests. What happens is whenever that function f is called, the value that is passed in for followerName is always the last one that was in the Grail.followerMapping as it passed through the for loop.

local followerInfo, followerName, qualityLevel
for questId, followerId in pairs(Grail.followerMapping) do
	if Grail:MeetsRequirementFaction(questId) then
		followerInfo = C_Garrison.GetFollowerInfo(followerId)
		followerName = followerInfo.name
		qualityLevel = followerInfo.quality
		tinsert(t, { sortName = followerName, displayName = ITEM_QUALITY_COLORS[qualityLevel].hex..followerName.."|r", mapID = 0, f = function() Grail:SetMapAreaQuests(0, followerName, { questId }) Wholly.zoneInfo.panel.mapId = 0 Wholly._ForcePanelMapArea(Wholly, true) CloseDropDownMenus() end })
	end
end

A fix that seems to work properly is to change the scope of the followerName variable such that is is defined within the loop itself as the following code shows:

local followerInfo, qualityLevel
for questId, followerId in pairs(Grail.followerMapping) do
	if Grail:MeetsRequirementFaction(questId) then
		followerInfo = C_Garrison.GetFollowerInfo(followerId)
		local followerName = followerInfo.name
		qualityLevel = followerInfo.quality
		tinsert(t, { sortName = followerName, displayName = ITEM_QUALITY_COLORS[qualityLevel].hex..followerName.."|r", mapID = 0, f = function() Grail:SetMapAreaQuests(0, followerName, { questId }) Wholly.zoneInfo.panel.mapId = 0 Wholly._ForcePanelMapArea(Wholly, true) CloseDropDownMenus() end })
	end
end

Can someone enlighten me as to why this is the case?

[MunkDev]

That's because you're referencing the original followerName, not the value it held at the time you created the instance of the function. Since the original followerName was last overwritten by the last entry in Grail.followerMapping, all the functions will refer to that data. Think memory address, not value.

In your second code snippet you create a separate instance of followerName for each iteration, meaning each followerName has its own memory assigned and its own address. If you don't use the variables outside the for loop then there really is no reason to reference outside that scope.