Rails - Jan 2008 - Dynamic Finders don't give Exceptions? Or I can't get any...

Hi,

This has been bugging me a bit.

If I do the code:

begin
  user = User.find(:id)
rescue
  flash[:notice] = "Invalid ID"
else
  # rest of code
end

It works fine catching an invalid ID. However this code:

begin
  user = User.find_by_email(:email)
rescue
  flash[:notice] = "Invalid Email"
else
  # rest of code
end

Never raises an exception and I have to check if ''user ==
nil''. This is
irritating because it means my code has to be structured differently in
each case. Am I doing something wrong? I''d like to have one style of
error checking after every database read, for clarity.

Cheers
Theo
-- 
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On Jan 11, 2008 12:01 AM, Theo Graham-brown
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> Hi,
>
> This has been bugging me a bit.
>
> If I do the code:
>
> begin
>   user = User.find(:id)
> rescue
>   flash[:notice] = "Invalid ID"
> else
>   # rest of code
> end
>
> It works fine catching an invalid ID. However this code:
>
> begin
>   user = User.find_by_email(:email)
> rescue
>   flash[:notice] = "Invalid Email"
> else
>   # rest of code
> end
>
> Never raises an exception and I have to check if ''user ==
nil''. This is
> irritating because it means my code has to be structured differently in
> each case. Am I doing something wrong? I''d like to have one style
of
> error checking after every database read, for clarity.
>
> Cheers
> Theo
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
There''s a sidebar in AWDWR that discusses that.  The gist is that if
you do User.find(1), then you expect that record to exist.  If you do
User.find_by_some_attribute("foo"), then it''s more of a scan,
and not
finding a result isn''t exceptional.

You can use User.find_by_id(1) if you want those same no-error
semantics.  I think it''s best to use whichever expresses your intent
better, rather than simply trying for uniformity.

Pat

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Pat Maddox wrote:
> On Jan 11, 2008 12:01 AM, Theo Graham-brown
> <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>>   flash[:notice] = "Invalid ID"
>> else
>> --
>> Posted via http://www.ruby-forum.com/.
>>
>> >
>>
> 
> There''s a sidebar in AWDWR that discusses that.  The gist is that
if
> you do User.find(1), then you expect that record to exist.  If you do
> User.find_by_some_attribute("foo"), then it''s more of a
scan, and not
> finding a result isn''t exceptional.
> 
> You can use User.find_by_id(1) if you want those same no-error
> semantics.  I think it''s best to use whichever expresses your
intent
> better, rather than simply trying for uniformity.
> 
> Pat
Okay, that makes sense. I''ll leave it as it is, then. I worry that I am
a very poor Rails programmer, you see.

With PHP/C#/C++/C/Java stuff it''s so well documentated that you can 
quickly see when you''re writing in a clear and correct style, but I
just
don''t know enough about Rails to know if I''m making a mess of
things.

Cheers
Theo
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On Jan 11, 2008 12:22 AM, Theo Graham-brown
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> Pat Maddox wrote:
> > On Jan 11, 2008 12:01 AM, Theo Graham-brown
> > <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> >>   flash[:notice] = "Invalid ID"
> >> else
> >> --
> >> Posted via http://www.ruby-forum.com/.
> >>
> >> >
> >>
> >
> > There''s a sidebar in AWDWR that discusses that.  The gist is
that if
> > you do User.find(1), then you expect that record to exist.  If you do
> > User.find_by_some_attribute("foo"), then it''s more
of a scan, and not
> > finding a result isn''t exceptional.
> >
> > You can use User.find_by_id(1) if you want those same no-error
> > semantics.  I think it''s best to use whichever expresses your
intent
> > better, rather than simply trying for uniformity.
> >
> > Pat
>
> Okay, that makes sense. I''ll leave it as it is, then. I worry that
I am
> a very poor Rails programmer, you see.
>
> With PHP/C#/C++/C/Java stuff it''s so well documentated that you
can
> quickly see when you''re writing in a clear and correct style, but
I just
> don''t know enough about Rails to know if I''m making a
mess of things.
Pick up a copy of Obie''s book, The Rails Way.  It''s all about
documenting the Rails way of doing things.

Pat

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