class methods in ruby

gistfile1.rb

class Article
  #class method
  def self.publish
    .......
  end
end

# all class methods
class << Article
  def publish
    ...
  end

  def annouce
    ....
  end
end

# mix of instance and class methods.
class Article

  def initialize(content)
    ...
  end

  #instance method
  def addContent
    ...
  end

  class << self

    def publish
      ....
    end

    def announce
      ....
    end
  end

end