waldyrious / metafields.jl

Extra info about your julia fields

MetaFields

This package allows defining metadata for fields in a struct, similar to tags in go. But named and inifitely extensible.

They use a similar syntax to Parameters.jl, with a | bar instead of =. You can, in fact, use it as a replacement for Parameters.jl with the aid of Defaults.jl.

@metafield describe ""

@describe mutable struct Described
   a::Int     | "an Int with a description"  
   b::Float64 | "a Float with a description"
end

d = Described(1, 1.0)

julia>describe(d, :a) 
"an Int with a description"  

julia>describe(d, :b) 
"a Float with a description"  

julia>describe(d, :c) 
""  

A more complex example :

using Parameters
@metafield describe ""
@metafield paramrange [0, 1]

@describe @paramrange @with_kw struct Keyword{T}
    a::T = 3 | [0, 100] | "a field with a range, description and default"
    b::T = 5 | [2, 9]   | "another field with a range, description and default"
end

k = Keyword()

julia> describe(k, :b) 
"another field with a range, description and default"

julia> paramrange(k, :a) 
[0, 100]
""  

You can chain as many metafields together as you want.

Just remember that the data for the first @metafield macro goes at the end on the line in the struct. This makes sense when you consider that @with_kw from Parameters.jl has to be the last macro, but the first item in the row after the field type.

You can also update or add fields on a type that is already declared using the same syntax, but you don't need to include all fields, or even their types.