From: Joel Pearson <lists@...>
Date: 2012-10-25T08:17:30+09:00
Subject: Re: Exception handelling in ruby

Brian Candler wrote in post #1080999:
> Joel Pearson wrote in post #1080729:
>> rescue => e
>> This rescues any error and lets you use 'e' as a variable to inspect the
>> error.
>
> That is incorrect.
>
> rescue => e
>
> only rescues exceptions which are StandardError and its descendants.
> That is, it is exactly the same as
>
> rescue StandardError => e
>
>> something like the below would catch errors 1 and 2 respectively, and if
>> the error didn't fall into those categories then the third rescue would
>> catch it.
>>
>> rescue 1
>> rescue 2
>> rescue
>
> No, a bare "rescue" also only captures StandardError and its children.
>
> If you want to rescue *absolutely every* exception then you need to
> write explicitly:
>
> rescue Exception
>
> However, as I said before, this is almost always a bad idea, because
> exceptions outside of StandardError are things you rarely want to catch;
> things that mean your interpreter has blown up in such a bad way that
> it's pointless attempting to continue, and catching it will only prolong
> the pain.

D'oh! I forgot that Exception covers more than the default rescue.
Brian is right, try to avoid rescuing something as all-encompassing as 
"Exception". If you want to know what your error is, you can do a test 
run which causes the failure, and try something like "e.class" to 
ascertain the type of error you need to handle.

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