rails console打印实例变量

class U
  attr_reader :name
  attr_writer :age
  attr_accessor :sex
  def initialize(name, age, sex, phone)
      @name = name
      @age = age
      @sex = sex
      @phone = phone
  end
end
u = U.new('yanlp', 11, '男', '13900000001')

u.name
=> "yanlp"
u.phone
NoMethodError: undefined method `phone' for #
u.methods.grep /instance/
=> [:instance_values,
 :instance_variable_names,
 :pretty_print_instance_variables,
 :instance_variables,
 :instance_variable_get,
 :instance_variable_set,
 :instance_variable_defined?,
 :remove_instance_variable,
 :instance_of?,
 :instance_eval,
 :instance_exec]
u.instance_values['phone']
=> "13900000001"
u.instance_variable_set(:@phone, '13900000002')
=> "13900000002"
u.instance_variable_get(:@phone)
=> "13900000002"
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