ruby - 如何重现 NilClass 的未定义方法错误

Question

我想了解如何在 Ruby 1.9 中重现以下错误：

NoMethodError (undefined method `[]' for nil:NilClass):

这是我自己的兴趣。以下对我不起作用：

a = nil
a[:key]

它产生以下错误：

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.[]

Answer 1

您的代码在我的机器上运行（提交答案，因为我无法格式化评论）：

⇨ irb
1.9.3p194 :001 > a = nil
 => nil 
1.9.3p194 :002 > a[:key]
  NoMethodError: undefined method `[]' for nil:NilClass
    from (irb):2
    from /Users/bjc/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'