Ruby中的private和protected

#private 声明的方法
#只能在实例方法中调用并且不能使用self
#子类可以调用

#protected
#只能在实例方法中调用能够使用self
#可以在本类或者子类的实例方法中使用 
#
class C1
    def c1
        puts 'public method'
    end
    
    def c2
        puts 'private method'
    end
    private :c2
    
    def c3 
        puts 'protect method'
    end
    protected :c3
   
  def test
    c2
    c3
    c = C1.new
    c.c3
  end
  def self.test2
    c2 #error
    c3 #error
    c = C1.new
    c.c3  #error
  end

end
C1.new.test
#C1.test2 =>error

class C2 < C1
    def test
        c2
    c3
    self.c3
    end
end
C2.new.test

class C3
    c1 = C1.new
    c1.c3#error
end