ex.class应该在这里等于什么？

Question

我正在尝试使用从本网站下载的代码来学习ruby .

我陷入了困境.

  def test_you_dont_get_null_pointer_errors_when_calling_methods_on_nil
    # What happens when you call a method that doesn't exist.  The
    # following begin/rescue/end code block captures the exception and
    # makes some assertions about it.
    begin
      nil.some_method_nil_doesnt_know_about
    rescue Exception => ex
      # What exception has been caught?
      assert_equal NoMethodError, ex.class

  # What message was attached to the exception?
  # (HINT: replace __ with part of the error message.)
  assert_match(/__/, ex.message)
end

结束

我应该用错误消息的一部分替换__,但我没有成功.好吧,我是,因为经过几次尝试后我只是用空格替换它,因为我认为错误信息在单词之间有空格.但我怎么看错误信息是什么？

Answer 1

你会在这里得到一个NoMethodError:

>> def tst
>>   nil.an_unknown_meth
>> rescue Exception => ex
>>   puts ex.class
>>   puts ex.message
>> end
 => nil 

>> tst
NoMethodError
undefined method `an_unknown_meth' for nil:NilClass

所以NoMethodError对于一个类,并且/undefined method .* for nil:NilClass/作为一个消息应该适合.

有关NoMethodError的更多信息以及ruby-docs中的Ruby Exceptions