Index Nill and Square Brackets

[circonian]

I have two questions if anyone can help me out. Thanks!

First Question:
Can anyone tell me why one of these works and the other does not?
TargetHPBar[1] turns out nil for ZO_TargetUnitFramereticleover, but it works for ZO_PlayerAttributeHealth

HPBar =       {ZO_PlayerAttributeHealth,      true, false, DEFAULT_ALPHA,   69,   0, 300, DEFAULT_SCALE},
TargetHPBar = {ZO_TargetUnitFramereticleover, true, false, DEFAULT_ALPHA,    0, 150, 300, DEFAULT_SCALE},

I'm trying to do this:

ConfigurableUI.BarSetup(TargetHPBar)
 
function ConfigurableUI.BarSetup(_BarTable)
    _Control, _Unlocked, _Hidden, _Alpha, _Posx, _Posy, _Width, _Scale = unpack(_BarTable)
    _Control:SetMovable(_Unlocked)
       ...
end

Second Question:
Looking at other addons I can't figure out what the difference is between some of the assignments I see like:

-- I see some like this...I get this one.
DAMAGE_COLOR         = { 1, 1, 1, 1 }
-- But I also see some with square brackets around them
[DAMAGE_TYPE_NONE]      = { 1, 1, 1, 1 }
-- Some also have single quotes in them
['ZO_ActionBar1'] = {1, myaddon.stuff}
-- Some also have double quotes in them
["enabled"] = true,

Whats the difference in those ? Why do some have square brackets, some have ['...'] and some have ["..."]?

Thanks

[Edda]

"blabla" and 'blabla' is exactly the same thing. "..." and '...' are used to delimit a string. In PHP they are slightly different ("..." lets you insert variables on the fly like : "my max health is $MaxHP"), not sure about Lua but afaik they are stricly the same.

The difference between DAMAGE_COLOR and [DAMAGE_COLOR] is that [] are used to define a table index so it's likely that [DAMAGE_COLOR] = stuff is part of a table, where DAMAGE_COLOR = stuff is just a variable defined with name DAMAGE_COLOR

Example without table :

DAMAGE_COLOR = "red"
HEAL_COLOR = "green"
BUFF_COLOR = "yellow"

Example with table :

local Colors = {} -- create an empty table
Colors.DAMAGE_COLOR = "red"
Colors.HEAL_COLOR = "green"
Colors.BUFF_COLOR = "yellow"

Or

local Colors = {} -- create an empty table
Colors["DAMAGE_COLOR"] = "red"
Colors["HEAL_COLOR"] = "green"
Colors["BUFF_COLOR"] = "yellow"

Which is the same thing.

Then you can access your colors with either i.e. Colors.DAMAGE_COLOR or Colors["DAMAGE_COLOR"].

Now for [DAMAGE_TYPE_NONE] without quotes this is different because the thing will return you the value with index of the DAMAGE_TYPE_NONE value.

Example :

local Colors = {"red", "green", "blue"}
local MY_SUPER_INDEX = 2
print(Colors[MY_SUPER_INDEX]) -- "green"
 
MY_SUPER_INDEX = 4
print(Colors[MY_SUPER_INDEX]) -- nil

To sum up : ".." or '..' is for string. [] is for table indexes. ["MyIndex"] is for value with index "MyIndex" and [MyIndex] is for value with index *content of MyIndex* - if that makes sense because with [MyIndex] the MyIndex is not considered an index but a variable.

Another silly example :

local index1 = "color1"
local index2 = "color2"
local index3 = "color3"
 
local Colors = {[index1] = "red", [index2] = "green", [index3] = "blue"}
 
print(Colors["color3"]) -- "blue"
print(Colors.color3) -- "blue"
print(Colors.index3) -- nil

About your first question : I think TargetHPBar[1] turns out nil because ZO_TargetUnitFramereticleover IS nil. Did you check for a typo ? Lua is case-sensitive.