Ruby Modules

ruby_modules1.rb

module A
  def self.a
    p 'self a'
  end
  
  def a
    p 'Aa'
  end
  
  def b 
    p 'Ab'
  end
end

class B
  include A
  
  def a
    p 'Ba'
  end
end

B.new.a # Ba
B.new.b # Ab
A.a # self a

A.new # NoMethodError: undefined method `new' for A:Module

ruby_modules2.rb

module A
  module B
    def self.nesting
      Module.nesting
    end
    class C
      def self.nesting
        Module.nesting
      end
    end
  end
end

A::B::C.new
A::B.nesting # [A::B, A]
A::B::C.nesting # [A::B::C, A::B, A]

ruby_modules3.rb

# http://www.railstips.org/blog/archives/2009/05/15/include-vs-extend-in-ruby/
module A
  def a
    p 'a'
  end
end

module B
  def b
    p 'b'
  end
end

module C
  def c
    p 'c'
  end
end

class E
  #include A
end

class D
  extend B
  
  class << self
    include C
  end
end

E.a # NoMethodError: undefined method `a' for E:Class
E.new.a # a
D.b # b
D.new.b # NoMethodError: undefined method `b' for #<D:0x007f8ebc83f160>
D.c # c
D.new.c # NoMethodError: undefined method `c' for #<D:0x007f8ebb906b08>

https://gist.github.com/mkurtikov/f42a4bd5c43f63e294bc4d84614f68ba#file-ruby_modules3-rb-L21 remove comment from #include A