HashInit

hashinit.rb

module HashInit

#example usage:

#  instead of this -
#  
#  class Message
#    attr_reader :content, :sender, :subject
#    attr_accessor :event
#    def initialize(message)
#        @content, @sender, @subject, @event =
#          message[:content], message[:sender], message[:subject], message[:event]
#    end

# type this -
#
#  class Message
#    attr_reader :content, :sender, :subject
#    attr_accessor :event
#    include HashInit
#    def initialize(message)
#      init_ivars message
#    end

  def init_ivars(hash)
    hash.each do |k,v|
      set_ivar_from_hash(k,v)
    end
  end

# can't really recommend using attr_ methods below, but I included them for good measure :-)

  def attr_accessor_init(hash)
    hash.each do |k,v|
      set_ivar_from_hash(k,v)
      add_attr_reader(k)
      add_attr_writer(k)
    end
  end

  def attr_reader_init(hash)
    hash.each do |k,v|
      set_ivar_from_hash(k,v)
      add_attr_reader(k)
    end
  end

  def attr_writer_init(hash)
    hash.each do |k,v|
      set_ivar_from_hash(k,v)
      add_attr_writer(k)
    end
  end

  private

  def set_ivar_from_hash(key, value)
    self.instance_variable_set("@#{key}", value)
  end

  def add_attr_reader(key)
    self.class.send(:define_method, key, proc{self.instance_variable_get("@#{key}")})
  end

  def add_attr_writer(key)
    self.class.send(:define_method, "#{key}=", proc{|v| self.instance_variable_set("@#{key}", v)})
  end
end

I suggest you take a look at https://github.com/intridea/hashie