Looong methods! And code in the initializer!

model.rb

module Id::Model

  def initialize(data = {})
    @data = data.reduce({}) do |acc, (k, v)|
      field = fields[k.to_sym]
      v ||= field.default!
      v = field.type.new(v) if field.type.is_a?(Id::Model) && !v.nil?
      acc.merge(k.to_s => Id::Hashifier.enhash(v))
    end
  end

  def set(update)
    updated = data.merge(update.stringify_keys)
    self.class.new(updated)
  end

  def unset(*fields)
    fields  = fields.map(&:to_s)
    updated = data.except(*fields)
    self.class.new(updated)
  end

  def eql? other
    other.is_a?(Id::Model) && other.data.eql?(self.data)
  end
  alias_method :==, :eql?

  def hash
    data.hash
  end

  attr_reader :data
  alias_method :to_hash, :data

  def self.included(base)
    base.send :extend, Id::Field, Id::Association, Id::EtaExpansion
  end
end

I think the initializer is doing too much. Indoctrinated as I am, dogmatic as I may sound! Id::Hashifier looks like a good candidate (only by name obviously) for this functionality.

Also, mutation on line 18- tsk tsk.