class Person
  attr_accessor :name
  def initialize(name)
    @name = name
  end

module Sortable
  def sort(options={})
    attributes = options[:attributes].inject("["){|attribute_string, attribute| attribute_string << "object.#{attribute},"} + "]"
    options[:collection].sort_by{|object| eval(attributes)}
  end

class Animal
    def speak
        "please override me"
    end
end

class Person
  attr_accessor :name
  def greeting
    "Hello I'm #{@name}"
  end

a = [1,2,3,4]
p a
a << 5
p a
a.push(6,7,8)

module Sortable
  def sort(options={})
    attributes = options[:attributes].inject("["){|attribute_string, attribute| attribute_string << "object.#{attribute},"} + "]"
    options[:collection].sort_by{|object| eval(attributes)}
  end

class Person
  attr_accessor :lastname,:firstname,:age
  def initialize(firstname,lastname,age)
    @lastname = lastname
    @firstname = firstname

class Person
  include Comparable
  attr_accessor :name
  def initialize(name)
    @name = name

#comparable operator <=>
# natural ordering
# 1 2 3 4...
# a b c
puts 1 <=> 1

class CourseEvaluation
  attr_accessor :title,:teacher
  def initialize(title,teacher)
    @title,@teacher = title, teacher
    @comments = []

module Commentable
  def initialize
    @comments = []
  end
  def add_comment(comment)

module ClassMethods
  def run
    puts "I'm running..."
  end
end

#RUBYISMS

a = b.foo
if a.empty?
  a = b.bar

#RUBYISMS

a = b.foo
if a.empty?
  a = b.bar

#RUBYISMS

a = b.foo
if a.empty?
  a = b.bar