Iterate through vars without a index? - variables

Question

I set some vars like this:
local var1Age = 10
local var2Age = 20
local var3Age = 30
Now I want to iterate them with a loop like this:
for i=1, 3 do
if var..i..Age >= 21 then
print("yep")
end
end
I can't change the vars, or create a table instead. Is it possible somehow with this vars?
Edit:
I could do something like this:
if var1Age >= 21 then
print("yep")
end
if var2Age >= 21 then
print("yep")
end
if var3Age >= 21 then
print("yep")
end
But I have ~50 vars like that. That's why I search a way to do it with a loop.
Edit2:
The vars are set by a class I can't change, so I can't change the way the vars are set.
For example I can't set the vars like this:
local varAge = {}
varAge[1] = 10
varAge[2] = 20
varAge[3] = 30
Edit3:
The class saves the vars in a table like this: http://ideone.com/iO4I8N

Answer 1

You could iterate through all local variables via debug.getlocal and filter variables you're interested in by name. http://www.lua.org/pil/23.1.1.html
Here is example on how to use it.
local var1Age = 10
local var2Age = 20
local var3Age = 30
function local_var_value(n)
local a = 1
while true do
local name, value = debug.getlocal(2, a)
if not name then break end
if name == n then
return value
end
a = a + 1
end
end
for i=1, 3 do
local v = local_var_value("var"..i.."Age")
if v and v >= 21 then
print("yep")
end
end

Answer 2

Are you really sure you want to stretch the language usage this far? The use of debug library should be left for advanced use when you cannot do otherwise.
Maybe your programming problem could be solved in a more elegant way using "regular" Lua facilities. To have a sequence of variables indexed by a number, simply use a table as an array:
local varAge = {}
varAge[1] = 10
varAge[2] = 20
varAge[3] = 30
for i=1,#varAge do
if varAge[i] >= 21 then
print("yep")
end
end
EDIT
If you really need to use debug.getlocal and performance is really an issue, you can avoid the potential O(n2) behavior scanning the locals only once and storing their values in a table:
local var1Age = 10
local var2Age = 20
local var3Age = 30
local function GetLocalVars( level )
local result = {}
for i = 1, math.huge do
local name, value = debug.getlocal( level, i )
if not name then break end
result[ name ] = value
end
return result
end
local local_vars = GetLocalVars( 2 )
for i = 1, 3 do
local name = "var"..i.."Age"
local v = local_vars[ name ]
if v and v >= 21 then
print("yep")
end
end

Answer 3

Based on the sample code you provided from your comment here, You should be able to iterate through your data structure without ever needing to use debug.getlocal.
local vars = varcount(DTClass)
for i = 1, vars do
local vari = "var" .. i
local variAge = DTClass[vari.."Age"]
if variAge and variAge >= 21 then
print(DTClass[vari.."Weight"])
end
end
This should work whether DTClass is a table or a userdata assuming it provides a suitable __index. Of course you need some way to determine total elements in DTClass. Just implement the varcount function to do this.
If DTClass is a table, varcount can be as simple as return #DTClass / var_fields.