Rails - Oct 2009 - Return "title" column if "caption" column is empty?

Hi all

Oh my god, this really shouldn''t be a tough one, but I just
don''t get
it. ;-)

class Page < ActiveRecord::Base
  def caption
    caption ? caption : title
  end
end

I want to return the content of the title column when the caption column
is empty:

p.caption # Caption is not empty
# => "caption"

p.caption # Caption is empty
# => "title"

Not astonishing, I get a StackLevelTooDeep Exception with my
"solution"
above... But how can I do it right?

Thanks a lot... My brain is just a bit wrecked today...
Josh
-- 
Posted via http://www.ruby-forum.com/.

On Wed, Oct 7, 2009 at 11:11 AM, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> class Page < ActiveRecord::Base
>  def caption
>    caption ? caption : title
>  end
> end
This will produce an infinite loop.  I think you want something more like

self.caption ? self.caption : self.title

But honestly I''d rename the method to something else for clarity.



-- 
Greg Donald
http://destiney.com/

> On Wed, Oct 7, 2009 at 11:11 AM, Joshua Muheim
> <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>> class Page < ActiveRecord::Base
>>  def caption
>>    caption ? caption : title
>>  end
>> end
>
> This will produce an infinite loop.  I think you want something more  
> like
>
> self.caption ? self.caption : self.title
>
> But honestly I''d rename the method to something else for clarity.
Agreed.  At some point you''re going to want to access
''caption''
directly and the above won''t let you do that.

Plus your team might not realize you''re adding magic.

I''ve always gone with "preferred"... that is..

def preferred_caption
   # code to get me the ideal caption for the fields available
end

That helps remind me that I''m not necessarily getting back the caption
itself, but the ideal caption for the given situation.

It''s worked well for me so far.

-philip

Use read_attribute(:caption).

2009/10/7, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>
> Hi all
>
> Oh my god, this really shouldn''t be a tough one, but I just
don''t get
> it. ;-)
>
> class Page < ActiveRecord::Base
>   def caption
>     caption ? caption : title
>   end
> end
>
> I want to return the content of the title column when the caption column
> is empty:
>
> p.caption # Caption is not empty
> # => "caption"
>
> p.caption # Caption is empty
> # => "title"
>
> Not astonishing, I get a StackLevelTooDeep Exception with my
"solution"
> above... But how can I do it right?
>
> Thanks a lot... My brain is just a bit wrecked today...
> Josh
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
-- 
Von meinen Mobilgerät aus gesendet

Thanks for your useful hints, guys. :-)
-- 
Posted via http://www.ruby-forum.com/.

super might work too

  def caption
    super ? super : title
  end


On Oct 7, 5:26 pm, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Thanks for your useful hints, guys. :-)
> --
> Posted viahttp://www.ruby-forum.com/.

Mauricio Szabo wrote:
> super might work too
> 
>   def caption
>     super ? super : title
>   end
But it won''t, because caption is not defined on the superclass.
> 
> 
> On Oct 7, 5:26�pm, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7m5VldFQK4jKA@public.gmane.orgt>
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

Have you tested it? I tried on a test application, and it works...

On Oct 8, 9:06 am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
s.net> wrote:
> Mauricio Szabo wrote:
> > super might work too
>
> >   def caption
> >     super ? super : title
> >   end
>
> But it won''t, because caption is not defined on the superclass.
>
>
>
> > On Oct 7, 5:26 pm, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
>
> Best,
> --
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
> --
> Posted viahttp://www.ruby-forum.com/.

Mauricio Szabo wrote:
> Have you tested it? I tried on a test application, and it works...
Hmm.  Maybe ActiveRecord''s method_missing trickery strikes
again...
> 
> On Oct 8, 9:06�am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

Also I am not sure what rails default is when you just add a
"?"....does it only fail if caption is nil?

I like to do something like this in these scenarios:

def the_caption
  self.caption.blank? title : caption
end

I haven''t used read_attribute yet but from the docs it might look
something like this

def caption
      caption = read_attribute(:caption)
      caption.blank? self.title : caption
end

You get the idea though....just wanted to mention the "blank" part
because if your caption is somehow set to " " I am guessing you want
the title returned.

On Oct 8, 9:43 am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
s.net> wrote:
> Mauricio Szabo wrote:
> > Have you tested it? I tried on a test application, and it works...
>
> Hmm.  Maybe ActiveRecord''s method_missing trickery strikes
again...
>
>
>
> > On Oct 8, 9:06 am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
>
> Best,
> --
> Marnen Laibow-Koserhttp://www.marnen.org
> mar...-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
> --
> Posted viahttp://www.ruby-forum.com/.

def caption
  self[:caption] || title
end

On Oct 8, 5:11 am, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Hi all
>
> Oh my god, this really shouldn''t be a tough one, but I just
don''t get
> it. ;-)
>
> class Page < ActiveRecord::Base
>   def caption
>     caption ? caption : title
>   end
> end
>
> I want to return the content of the title column when the caption column
> is empty:
>
> p.caption # Caption is not empty
> # => "caption"
>
> p.caption # Caption is empty
> # => "title"
>
> Not astonishing, I get a StackLevelTooDeep Exception with my
"solution"
> above... But how can I do it right?
>
> Thanks a lot... My brain is just a bit wrecked today...
> Josh
> --
> Posted viahttp://www.ruby-forum.com/.

@Joshua - FYI self[:caption] <=> read_attribute(:caption)

@Chris - ...and I am guessing interchangeable with self.caption

On Oct 9, 5:27 am, Chris
<c.bartl...-wUU9E3n5/m4qAMOr+u8IRA@public.gmane.org>
wrote:
> def caption
>   self[:caption] || title
> end
>
> On Oct 8, 5:11 am, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
> wrote:
>
> > Hi all
>
> > Oh my god, this really shouldn''t be a tough one, but I just
don''t get
> > it. ;-)
>
> > class Page < ActiveRecord::Base
> >   def caption
> >     caption ? caption : title
> >   end
> > end
>
> > I want to return the content of the title column when the caption
column
> > is empty:
>
> > p.caption # Caption is not empty
> > # => "caption"
>
> > p.caption # Caption is empty
> > # => "title"
>
> > Not astonishing, I get a StackLevelTooDeep Exception with my
"solution"
> > above... But how can I do it right?
>
> > Thanks a lot... My brain is just a bit wrecked today...
> > Josh
> > --
> > Posted viahttp://www.ruby-forum.com/.

Afaik it has nothing to do with method missing magic. Its just that if
you overwrite a method, a call to super invokes the original method.
AR injects accessor methods for every table column into the class.

2009/10/8, Marnen Laibow-Koser
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>
> Mauricio Szabo wrote:
>> Have you tested it? I tried on a test application, and it works...
>
> Hmm.  Maybe ActiveRecord''s method_missing trickery strikes
again...
>>
>> On Oct 8, 9:06�am, Marnen Laibow-Koser <rails-mailing-l...@andreas-
>
> Best,
> --
> Marnen Laibow-Koser
> http://www.marnen.org
> marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
-- 
Von meinen Mobilgerät aus gesendet

mike wrote:
> Afaik it has nothing to do with method missing magic. Its just that if
> you overwrite a method, a call to super invokes the original method.
Not really.  As far as I know, super calls the method of the same name 
*in the parent class*, which isn''t always the same thing. 
That''s why we
have alias_method_chain -- it wouldn''t be necessary if super worked the
way you claim.
> AR injects accessor methods for every table column into the class.
But into the model class itself, not AR::Base.  There is no 
AR::Base#caption method for super to call.  I suspect that super simply 
triggers AR''s method_missing, which happens to do the right thing in 
this case.  But that shouldn''t be relied on as a general rule c
> 
> 2009/10/8, Marnen Laibow-Koser
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>> Marnen Laibow-Koser
>> http://www.marnen.org
>> marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
>> --
>> Posted via http://www.ruby-forum.com/.
>>
>> >
>>
> 
> --
> Von meinen Mobilgerät aus gesendet
-- 
Posted via http://www.ruby-forum.com/.