# @track things. HOWTO: Is it possible to create global scope variable from local scope (function)
**URL:** https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814
**Category:** General Usage
**Tags:** question, metaprogramming
**Created:** [February 20, 2022, 7:07pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814 "2022-02-20T19:07:57Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 20, 2022, 7:07pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/1 "2022-02-20T19:07:57Z")
Hey Julianners,
I want something like this:
```julia
function fn(m)
# very compley function... and "m" would be a complex shit... that is hard to print
@track modelsss m[1]=4+9 # mimicing a possible case
# ex.: using m[1] later on
end
c=[3,4]
fn(c)
modelsss
```
I have this @track macro:
```julia
macro track(var, ex)
esc(quote
((@isdefined $var) == false) && ($var = []); # create the variable... but it is only LOCAL scope :(
res = $ex
push!($var, res)
end)
end
```
But this create a local variable.
Is this even possible? Or I have to have a evasion maneuver like creating the variable outside and calling global beforehand ☹
Bests!
Marcell
---
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 20, 2022, 7:12pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/2 "2022-02-20T19:12:05Z")
Wow I think I solved…
```julia
macro track(var, ex)
esc(quote
((@isdefined $var) == false) && (global $var = []);
res = $ex
push!($var, res)
end)
end
```
I didn’t know if this is this easy… :o Julia constinously suprise me!
Anyway I hope it is a useful macro for everyone! 😉
---
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 20, 2022, 7:17pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/3 "2022-02-20T19:17:12Z")
One more improvement, so we don’t run our expression’s return:
```julia
macro track(var, ex)
esc(quote
((@isdefined $var) == false) && (global $var = []);
res = $ex
push!($var, res)
res
end)
end
```
---
### Author:  [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)
#### Post date: [February 20, 2022, 8:26pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/4 "2022-02-20T20:26:38Z")
You’ll want to selectively escape `var` and `ex` rather than the whole block.
---
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 20, 2022, 8:51pm UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/5 "2022-02-20T20:51:53Z")
What is the difference in the behind?
I lack too much knowledge to implement this on the macro field in spite I tried to understand a year before:
```julia
macro track(vari, ex)
eva = esc(vari)
eex = esc(ex)
quote
((@isdefined $eva) == false) && (global $eva = []);
res = $eex
push!($eva, res)
res
end
end
```
This is somehow terribly wrong. And errors everywhere… 😃
I used escaping too long time ago and just cannot remeber how to do it… 😕
---
### Author:  [@tk3369](https://discourse.julialang.org/u/tk3369)
#### Post date: [February 21, 2022, 4:33am UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/6 "2022-02-21T04:33:22Z")
My video could be helpful here 🙂
[ ](https://www.youtube.com/watch?v=JePBb9-ychE)
---
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 21, 2022, 7:47am UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/7 "2022-02-21T07:47:43Z")
I stuck with a "module scope variable @isdefined checkin sadly… :
```julia
macro track(vari, ex)
eva = esc(vari)
eex = esc(ex)
quote
esc(((@isdefined $((vari))) == false) && (global $vari = []));
res = $eex
push!($eva, res)
res
end
end
```
I don’t know how to check the “vari” in the “Main.” scope I think.
---
### Author:  [@Marcell\_Havlik](https://discourse.julialang.org/u/Marcell_Havlik)
#### Post date: [February 21, 2022, 7:53am UTC](https://discourse.julialang.org/t/track-things-howto-is-it-possible-to-create-global-scope-variable-from-local-scope-function/76814/8 "2022-02-21T07:53:45Z")
Ok, I think I do this and at least I make a little macro higiene:
```julia
macro track(var, ex)
res = gensym()
esc(quote
((@isdefined $var) == false) && (global $var = []);
$res = $ex
push!($var, $res)
$res
end)
end
```