An HStruct that also contains type data,

typed_struct.rb

require 'hstruct'

class TypedStruct < HStruct
  def self.schema(schema = nil)
    @__schema ||= schema
  end
end

def TypedStruct(members_hash, &block)
  member_names = members_hash.keys

  TypedStruct.new(*member_names, &block).tap { |struct|
    struct.schema(members_hash)
  }
end

# Example

Condition = TypedStruct(
    id:            String,
    concept_id:    Fixnum,
    started_at:    Time,
    finished_at:   Time,
    patient_id:    String,
    medications:   Array,
    procedures:    Array,
    professionals: Array,
) do
  # ...
end

p Condition.schema
 =>
  {
                 :id => String < Object,
         :concept_id => Fixnum < Integer,
         :started_at => Time < Object,
        :finished_at => Time < Object,
         :patient_id => String < Object,
        :medications => Array < Object,
         :procedures => Array < Object,
  }

Not sure if I like the uppercase method overloading but mimicking the way that Struct.new returns a class is a bit crazy.

If you're curious check out the rubinius implementation of Struct https://github.com/rubinius/rubinius/blob/f290f2a4f7c59894ea567f9cb05cbe00a31a6654/kernel/common/struct.rb