Rails - Nov 2005 - Handling a nil value when using FileColumn's url_for_file_column

Being a Ruby newbie I don''t know how to properly check for a nil value.

In my view I have the following code (uses FileColumn):

<%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail", "thumb")
) %>

Problem is that for sometimes there isn''t a gallery_thumbnail and when
that
happens it blows up with the following error:

You have a nil object when you didn''t expect it!
You might have expected an instance of Array.
The error occured while evaluating nil.first

I''ve tried the following tests with no luck:

<%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail", "thumb")
unless @gallery.gallery_thumbnail.nil? ) %>

<%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail", "thumb")
unless @gallery.gallery_thumbnail == nil ) %>

<%= url_for_file_column( "gallery", "gallery_thumbnail",
"thumb" ) if
!@gallery.gallery_thumbnail.nil? %>

How should I be testing for this? What is the proper Ruby way for handling
nil values?

Kyle Heon
kheon-Wuw85uim5zDR7s880joybQ@public.gmane.org

On Nov 11, 2005, at 4:43 PM, Kyle Heon wrote:
> Being a Ruby newbie I don''t know how to properly check for a nil  
> value.
>
> In my view I have the following code (uses FileColumn):
>
> <%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail",
> "thumb")
> ) %>
>
> Problem is that for sometimes there isn''t a gallery_thumbnail and
> when that
> happens it blows up with the following error:
>
> You have a nil object when you didn''t expect it!
> You might have expected an instance of Array.
> The error occured while evaluating nil.first
>
> I''ve tried the following tests with no luck:
>
> <%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail",
> "thumb")
> unless @gallery.gallery_thumbnail.nil? ) %>
>
> <%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail",
> "thumb")
> unless @gallery.gallery_thumbnail == nil ) %>
>
> <%= url_for_file_column( "gallery",
"gallery_thumbnail", "thumb" ) if
> !@gallery.gallery_thumbnail.nil? %>
>
> How should I be testing for this? What is the proper Ruby way for  
> handling
> nil values?
>
> Kyle Heon
> kheon-Wuw85uim5zDR7s880joybQ@public.gmane.org

Kyle-

	This idiom works good for me when using the url_for_file_column and  
other things that will blow up if there is a nil value. I would  
rather it just do nothing when there is a nil. So here is how I  
handle it:
> <%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail",
> "thumb")) rescue nil %>

HTH-

-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
http://yakimaherald.com
509-577-7732
ezra-gdxLOakOTQ9oetBuM9ipNAC/G2K4zDHf@public.gmane.org

Hmm, that''s odd. I am pretty sure I tried that as well and it
didn''t work.
Who knows, it''s working now.

Now, one more question. What would be the "Rails" way of defaulting to
a "no
image" image in this same situation?

Sorry for all the questions.

Thanks for the tip!

Kyle Heon
kheon-Wuw85uim5zDR7s880joybQ@public.gmane.org

Kyle-

	This idiom works good for me when using the url_for_file_column and
other things that will blow up if there is a nil value. I would rather it
just do nothing when there is a nil. So here is how I handle it:
> <%= image_tag( url_for_file_column("gallery",
"gallery_thumbnail",
> "thumb")) rescue nil %>

HTH-

-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
http://yakimaherald.com
509-577-7732
ezra-gdxLOakOTQ9oetBuM9ipNAC/G2K4zDHf@public.gmane.org