# Capture part of return type
**URL:** https://discourse.julialang.org/t/capture-part-of-return-type/43139
**Category:** General Usage
**Tags:** parametric-types
**Created:** [July 15, 2020, 5:57pm UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139 "2020-07-15T17:57:45Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@grahamas](https://discourse.julialang.org/u/grahamas)
#### Post date: [July 15, 2020, 5:57pm UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139/1 "2020-07-15T17:57:45Z")
Is there a way to capture the type of a return in a variable (specifically a parameter of the variable type, but baby steps)
```julia
function f()
A::AbstractArray{T} where T = [1.0 2.0]
return T
end
```
Of course I can pretty easily get this info otherwise, but this syntax _almost_ seems like it makes sense. Almost, because it’s not quite clear how you’d get the scoping to work.
edit: Honestly, I’d also be happy with hearing about some non-syntactic way to say something like
```julia
@get_type T AbstractArray{T} typeof(A)
```
where it pattern matches and sets the T variable.
edit 2: … is the answer just to use function dispatch? That’s the answer, isn’t it. Sorry for the noise.
---
### Author:  [@dpsanders](https://discourse.julialang.org/u/dpsanders)
#### Post date: [July 15, 2020, 6:07pm UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139/2 "2020-07-15T18:07:48Z")
Are you just looking for `eltype`?
```julia
julia> A = [1.0, 2.0]
2-element Array{Float64,1}:
1.0
2.0
julia> T = eltype(A)
Float64
```
---
### Author:  [@grahamas](https://discourse.julialang.org/u/grahamas)
#### Post date: [July 15, 2020, 6:24pm UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139/3 "2020-07-15T18:24:37Z")
Not quite. I’m actually doing more like `nt::NamedTuple{names} = (a = 1.0, b = 2.0)`. But this works for my particular purposes:
```julia
typenames(nt::NamedTuple{names}) where names = names
```
It’d be nice if there were a simple syntactic way to do this, but writing a little helper function is fine
---
### Author:  [@marius311](https://discourse.julialang.org/u/marius311)
#### Post date: [July 15, 2020, 6:47pm UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139/4 "2020-07-15T18:47:17Z")
I could be wrong but it seems you could write a macro which lets you have the syntax from your OP by creating the helper function you, and it could probably be pretty generic. Ie it would turn,
```julia
function f()
A::AbstractArray{T} where T = [1.0 2.0]
return T
end
```
into
```julia
function f()
A::AbstractArray{T} where T = [1.0 2.0]
T = ((::AbstractArray{T} where T)->T)(A)
return T
end
```
And you can imagine this kind of thing can be done pretty programatically. Just an idea.
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [July 16, 2020, 10:08am UTC](https://discourse.julialang.org/t/capture-part-of-return-type/43139/5 "2020-07-16T10:08:41Z")
> [@grahamas](#):
>
> But this works for my particular purposes:
>
> ```julia
> typenames(nt::NamedTuple{names}) where names = names
>
> ```
I am afraid I still don’t understand the question, but would
```julia
julia> keys((a = 1, b = 2))
(:a, :b)
```
help?
Also `fieldnames` in type space.