# Macro for unpack and copy
**URL:** https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416
**Category:** New to Julia
**Tags:** macros, struct, copy
**Created:** [June 23, 2021, 5:36am UTC](https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416 "2021-06-23T05:36:26Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@iHany](https://discourse.julialang.org/u/iHany)
#### Post date: [June 23, 2021, 5:36am UTC](https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416/1 "2021-06-23T05:36:27Z")
Hi,
I’m frequently use [UnPack.jl](https://github.com/mauro3/UnPack.jl) to unpack data.
For example,
```julia
struct MyStr
a
b
end
mystr = MyStr(1, 2)
@unpack a, b = mystr # a, b = mystr.a, mystr.b
```
However, I sometimes need copy the unpacked values. For example,
```julia
struct MyStr
a
b
end
mystr = MyStr(1, 2)
@unpack a, b = mystr # a, b = mystr.a, mystr.b
a = copy(a)
b = copy(b)
```
Is there any macro that “unpack and copy” variables?
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [June 23, 2021, 6:36am UTC](https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416/2 "2021-06-23T06:36:40Z")
If it is specific to a type, you could define a special unpack method. See the last example in the README.
Otherwise, a feature could be to be able to specify a function to be applied before unpacking. In a sense similar to say `sum` which allows a function as input which is then applied to each element before summing. Not sure about the syntax though.
---
### Author:  [@iHany](https://discourse.julialang.org/u/iHany)
#### Post date: [June 23, 2021, 6:52am UTC](https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416/3 "2021-06-23T06:52:37Z")
> [@mauro3](#):
>
> Otherwise, a feature could be to be able to specify a function to be applied before unpacking. In a sense similar to say `sum` which allows a function as input which is then applied to each element before summing. Not sure about the syntax though.
For me, it’s an interesting way.
How about this form?
```julia
@unpack(:copy, a = mystr) # a = copy(mystr.a)
```
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [June 23, 2021, 7:16am UTC](https://discourse.julialang.org/t/macro-for-unpack-and-copy/63416/4 "2021-06-23T07:16:51Z")
That would need parenthesis for several outputs (unless you insist on the “:”, which I find odd)
For example:
```julia
@unpack copy a, b = A
@unpack(copy, (a, b = A))
```
Not sure about it though.