# "Nullable" (really "Nothingable") Types
**URL:** https://discourse.julialang.org/t/nullable-really-nothingable-types/55894
**Category:** General Usage
**Tags:** macros
**Created:** [February 23, 2021, 10:29pm UTC](https://discourse.julialang.org/t/nullable-really-nothingable-types/55894 "2021-02-23T22:29:56Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@astrobc1](https://discourse.julialang.org/u/astrobc1)
#### Post date: [February 23, 2021, 10:29pm UTC](https://discourse.julialang.org/t/nullable-really-nothingable-types/55894/1 "2021-02-23T22:29:56Z")
I’m curious if there’s a proper Julian way to implement optional struct fields through an effective Union{T, Nothing}.
I’ve written the macro below and it seems to work for my very simple test case. Is there a better way to achieve this? I suppose there could also be a macro for specific fields instead of the whole struct.
```julia
macro optional(block::Expr)
struct_name = block.args[2]
fields_expr = block.args[3].args
fields = Expr[]
for field ∈ fields_expr
if typeof(field) !== LineNumberNode
s = field.args[1]
t = field.args[2]
new_field = :($(s)::Union{$(t), Nothing})
push!(fields, new_field)
end
end
esc(quote
struct $struct_name
$(fields...)
end
end)
end
@optional struct A
x::Float64
y::Float64
end
a = A(1.0, nothing)
println(a)
```
---
### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [February 23, 2021, 10:41pm UTC](https://discourse.julialang.org/t/nullable-really-nothingable-types/55894/2 "2021-02-23T22:41:56Z")
One other option would be something like
```julia
julia> macro var"?"(T)
esc(:(Union{$T, Nothing}))
end
@? (macro with 1 method)
julia> struct A
x:: @? Float64
y:: Float64
end
julia> f(x::@? A) = x
f (generic function with 1 method)
julia> f(nothing)
julia> f(A(nothing, 1))
A(nothing, 1.0)
```
---
### Author:  [@astrobc1](https://discourse.julialang.org/u/astrobc1)
#### Post date: [February 23, 2021, 10:47pm UTC](https://discourse.julialang.org/t/nullable-really-nothingable-types/55894/3 "2021-02-23T22:47:29Z")
Welp, I’m sold. That does sound like the best route! I didn’t even know one can use strings to define methods like you just did… Crazy stuff. Thanks!
---
### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [February 23, 2021, 11:27pm UTC](https://discourse.julialang.org/t/nullable-really-nothingable-types/55894/4 "2021-02-23T23:27:57Z")
One thing to note is that the `var` stringmacro was introduced in version `1.3`, but it’s a oneliner to define your own version:
```julia
julia> macro myvar_str(s) esc(Symbol(s)) end;
julia> myvar"a multiword variable name" = 1
1
julia> myvar"a multiword variable name"
1
```