From: Lloyd Zusman <ljz@...>
Date: 2005-03-03T08:02:35+09:00
Subject: Re: Erb: terminating a script?

Jamis Buck <jamis_buck@byu.edu> writes:

> On Mar 2, 2005, at 12:19 PM, Lloyd Zusman wrote:
>
>> William Ramirez Wrote:
>>
>>> On Wed, 2 Mar 2005 21:32:28 +0900, Lloyd Zusman <ljz@asfast.com>
>>> wrote:
>>>>   A<br>
>>>>   B<br>
>>>>   <% WHAT GOES HERE TO END THE SCRIPT? %>
>>>>   C<br>
>>>>   D<br>
>>>>
>>>> What do use for "WHAT GOES HERE ..." in order to cause the
>>>> processing to end after A and B print out?
>>>
>>> Just doing some quick reading, you may want to try exit or exit!, if
>>> you haven't already. If you have, what happened? Did it still output C
>>> and D?
>>>
>>> Apparently they're very similar, however, exit! ignores exception
>>> handling, at_exit functions, and finalizers.
>>
>> I did call exit, and it terminated the entire web server.  I forgot to
>> mention that I'm running Erb inside of ErbHandler within a webrick
>> FileHandler instance, not within a stand-alone CGI.  I'm sorry for
>> having left out that key piece of information in my original query.
>>
>> The same thing happened with the "exit!" method.
>
> Have you tried doing 'return'? Or perhaps 'break'? I haven't tried these
> myself, so I don't know if they will work or not. Just throwing out some
> ideas.

Yes, I have tried them.

Using 'return', I get this error:

  ERROR ThreadError: return can't jump across threads

Using 'break', I get this one:

  undefined method `result' for #<String:0x850bddc>

However, following up on the idea I mentioned in my previous message, I
did the following ... and it works:

  Original line in ErbHandler#do_GET ...

    res.body = evaluate(ERB.new(data), req, res)

  Replaced with ...

    res.body = evaluate(ERB.new('<% catch(:quit) { %>' +
                                data +
                                '<% } %>'), req, res)

Then, I can exit by doing a '<% throw :quit %>' from anywhere in the
page.  And any text that's specified before the 'throw' appears in the
resulting text.

The following also yields the same results:

    res.body = evaluate(ERB.new('<% lambda { %>' + data + '<% }.call %>')
                        req, res)

In this case, I can exit early by using either '<% break %>' or
'<% return %>'.  I like this one better, and this is what I have
just now implemented in my application.

Because of this, it seems to me that it would be beneficial if Erb were
to always put a lambda-call block around the text that gets evaluated.

I'm in favor of this enhancement going into a subsequent release, and
I'll soon submit a patch.

Thoughts or opinions?

-- 
 Lloyd Zusman
 ljz@asfast.com
 God bless you.