ER 6 Know How Ruby Build Inheritance Hierarachies ref: http://qiita.com/giwa/items/2390a3f93a9e8c474707

file0.txt

BasicObject
<- Kernel (module)
<- PP::ObjectMixin(module)
<- Object
<- Person
<- Customer

file1.rb

[3] pry(main)> class Person
[3] pry(main)*   def hi
[3] pry(main)*     puts 'hi'
[3] pry(main)*   end
[3] pry(main)* end

[4] pry(main)> class Customer < Person
[4] pry(main)* end


[11] pry(main)> Customer.superclass
=> Person

[12] pry(main)> Customer.singleton_class
=> #<Class:Customer>

[13] pry(main)> Customer.ancestors
=> [Customer, Person, Object, PP::ObjectMixin, Kernel, BasicObject]

[14] pry(main)> Customer.included_modules
=> [PP::ObjectMixin, Kernel]

[16] pry(main)> module PersonMixin
[16] pry(main)*   def name
[16] pry(main)*     puts 'foo'
[16] pry(main)*   end
[16] pry(main)* end

[18] pry(main)> Person.superclass
=> Object

[19] pry(main)> Customer.ancestors
=> [Customer, Person, PersonMixin, Object, PP::ObjectMixin, Kernel, BasicObject]

[20] pry(main)> module PersonMixin2
[20] pry(main)*   def name
[20] pry(main)*     puts 'bar'
[20] pry(main)*   end
[20] pry(main)* end
=> :name

[21] pry(main)> class Person
[21] pry(main)*   include PersonMixin
[21] pry(main)*   include PersonMixin2
[21] pry(main)* end
=> Person

[22] pry(main)> Customer.ancestors
=> [Customer,
 Person,
 PersonMixin2,
 PersonMixin,
 Object,
 PP::ObjectMixin,
 Kernel,
 BasicObject]

[28] pry(main)> Customer.superclass
=> Person

[29] pry(main)> Customer.superclass.superclass
=> Object

[30] pry(main)> Customer.superclass.superclass.superclass
=> BasicObject

[31] pry(main)> Customer.included_modules
=> [PersonMixin2, PersonMixin, PP::ObjectMixin, Kernel]

[37] pry(main)> customer = Customer.new
=> #<Customer:0x007f9de428f008>
[38] pry(main)> def customer.name
[38] pry(main)*   "baz"
[38] pry(main)* end

[42] pry(main)> customer.singleton_methods
=> [:name]

[43] pry(main)> customer.name
=> "baz"