dry-struct-bomb.rb

class User < Dry::Struct
  MissingAttribute = Class.new(NameError)

  def name
    [first_name, last_name].join(' ')
  end

  attribute :name, Dry::Types['strict.string']
  attribute :first_name, Dry::Types['strict.string']

  private

  def method_missing(*)
    super
  rescue NameError => error
    raise MissingAttribute.new("#{ error.message } (not loaded attribute?)")
  end
end

user = User.new(first_name: 'John', name: 'John Doe')
user.name