Error calling class methods from instance methods in Ruby

instance_and_class.rb

class HasInstanceMethods
  def instance_method
    puts "In instance method, the type of `self` is #{self.class}"
  end

  def self.class_method
    puts "In class method, the type of `self` is #{self.class}"
  end

  def call_class_from_instance
    begin
      class_method # raise NameError
    rescue Exception => e
      puts "raised #{e.inspect}"
    end
  end

  def call_self_class_from_instance
    self.class.class_method # works
  end

end


instance = HasInstanceMethods.new

instance.instance_method # works

HasInstanceMethods.class_method # works

# would raise NoMethodError:
# instance.class_method 

instance.call_class_from_instance # NameError

instance.call_self_class_from_instance # works

# ouptut:
# In instance method, the type of `self` is HasInstanceMethods
# In class method, the type of `self` is Class
# raised #<NameError: undefined local variable or method `class_method' for #<HasInstanceMethods:0x007fc88709d380>>
# In class method, the type of `self` is Class