How to create a private class method?

private doesn’t seem to work if you are defining a method on an explicit object (in your case self). You can use private_class_method to define class methods as private (or like you described).

class Person
  def self.get_name
    persons_name
  end

  def self.persons_name
    "Sam"
  end

  private_class_method :persons_name
end

puts "Hey, " + Person.get_name
puts "Hey, " + Person.persons_name

Alternatively (in ruby 2.1+), since a method definition returns a symbol of the method name, you can also use this as follows:

class Person
  def self.get_name
    persons_name
  end

  private_class_method def self.persons_name
    "Sam"
  end
end

puts "Hey, " + Person.get_name
puts "Hey, " + Person.persons_name