Composition and inheritance: the Julian way

General Usage
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5

You can always make a macro to avoid boilerplate code, e.g.:

abstract type AbstractPerson end

mutable struct Person <: AbstractPerson
    name::String
    age::Int
end


macro inherit(name, base, fields)
    base_type = Core.eval(@__MODULE__, base)
    base_fieldnames = fieldnames(base_type)
    base_types = [t for t in base_type.types]
    base_fields = [:($f::$T) for (f, T) in zip(base_fieldnames, base_types)]
    res = :(mutable struct $name end)
    push!(res.args[end].args, base_fields...)
    push!(res.args[end].args, fields.args...)
    return res
end


@inherit Citizen Person begin
    nationality::String
end

But honestly, I know very few tasks where field inheritance is indeed the best approach.

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