Ruby:如果出现正确的错误，我如何返回一个 bool 值？

Question

我有兴趣比较我的代码是否出现了正确的错误。如果引发正确的错误，则返回 true，否则返回 false。

有办法解决吗？还是我需要编写异常处理？

例如，

some_method(arg) == TypeError # => true

Answer 1

When an exception has been raised but not yet handled (in rescue, ensure, at_exit and END blocks) the global variable $! will contain the current exception and $@ contains the current exception’s backtrace.

按以下操作(使用内联 rescue 方式):

2.0.0-p0 :001 > [1, 2, 3].first("two")
TypeError: no implicit conversion of String into Integer
    from (irb):1:in 'first'
    from (irb):1
    from /home/kirti/.rvm/rubies/ruby-2.0.0-p0/bin/irb:16:in '<main>'
2.0.0-p0 :002 > [1, 2, 3].first("two") rescue $!.class == TypeError
 => true 
2.0.0-p0 :003 > [1, 2, 3]['a'] rescue $!.class == TypeError
 => true 
2.0.0-p0 :004 > [1, 2, 3]['a']
TypeError: no implicit conversion of String into Integer
    from (irb):4:in '[]'
    from (irb):4
    from /home/kirti/.rvm/rubies/ruby-2.0.0-p0/bin/irb:16:in '<main>'
2.0.0-p0 :005 > 1/0 rescue $!.class == TypeError
 => false 
2.0.0-p0 :006 > 

TypeError

Raised when encountering an object that is not of the expected type.

[1, 2, 3].first("two")

raises the exception: TypeError: no implicit conversion of String into Integer

在你的情况下你可以这样写:

some_method(arg) rescue $!.class == TypeError