thr3ads.net - Rails - Best way of handling nils in views? [Feb 2007]

If this information is useful, please help other people find it:
Share via:

Jake Cutter

2007-Feb-09 16:35 UTC

Best way of handling nils in views?

I find myself writing ugly code like the following a LOT:

<td><%=emp.title%></td>
<td><%=emp.department.name if !emp.department.nil? %></td>
<td><%=emp.site.name if !emp.site.nil?%></td>
<td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
emp.site.phone.empty?))
          emp.site.phone
        else
          "&nbsp;"
        end%>
</td>

Notice all those nil? checks? Is there no easier or cleaner way of
doing this?

Thanks,
Jake


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Jake Cutter

2007-Feb-09 16:40 UTC

head link

Re: Best way of handling nils in views?

Or...if you use table borders, you end up doing an even uglier
solution to avoid non-rendered cells for empty contents in Gecko-based
browsers (like Firefox):
<tr>
      <td><%=emp.last_name || "&nbsp;"%></td>
      <td><%=emp.first_name || "&nbsp;"%></td>
      <td><%=emp.title || "&nbsp;" %></td>
      <td><%=if !emp.department.nil?: emp.department.name else
"&nbsp"; end %></td>
      <td><%=emp.site.name if !emp.site.nil?%></td>
      <td><%=if (!emp.site.nil? and
                 (!emp.site.phone.nil? and !emp.site.phone.empty?))
               emp.site.phone
             else
               "&nbsp;"
             end%>
      </td>
      <td><%=emp.extension || "&nbsp;" %></td>
      <td><%=emp.mobile || "&nbsp;"%></td>
      <td><%=emp.pager|| "&nbsp;"%></td>
      <td><%=emp.alternate_phone||
"&nbsp;"%></td>
    </tr>


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Philip Hallstrom

2007-Feb-09 16:55 UTC

head link

Re: Best way of handling nils in views?

> I find myself writing ugly code like the following a LOT:
>
> <td><%=emp.title%></td>
> <td><%=emp.department.name if !emp.department.nil?
%></td>
> <td><%=emp.site.name if !emp.site.nil?%></td>
> <td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
> emp.site.phone.empty?))
>          emp.site.phone
>        else
>          "&nbsp;"
>        end%>
> </td>
>
> Notice all those nil? checks? Is there no easier or cleaner way of
> doing this?
Well, you could disable the whiny nil in config/environments/.... or you 
could fix them in the controller/model before they get to your view, or 
you could do one of these which is a little nicer:

obj.attr unless obj.attr.nil?
obj.attr rescue ''&nbsp;''

You might also try .blank? instead of .nil? in your &nbsp; cases.

-philip

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

George Ogata

2007-Feb-11 10:23 UTC

head link

Re: Best way of handling nils in views?

On 2/10/07, Jake Cutter <cutter38-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> I find myself writing ugly code like the following a LOT:
>
> <td><%=emp.title%></td>
> <td><%=emp.department.name if !emp.department.nil?
%></td>
> <td><%=emp.site.name if !emp.site.nil?%></td>
> <td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
> emp.site.phone.empty?))
>           emp.site.phone
>         else
>           "&nbsp;"
>         end%>
> </td>
>
> Notice all those nil? checks? Is there no easier or cleaner way of
> doing this?
Hmm, perhaps one of those "message-eating nils" [1] might have a place
here:

  class Object
    def blanker
      Blanker.new(self)
    end
  end

  class Blanker
    instance_methods.each{|name| undef_method(name) unless name =~ /\A__/}
    def initialize(receiver)
      @receiver = receiver
    end
    def to_s
      @receiver.to_s
    end
    def method_missing(*args)
      unless @receiver.nil?
        @receiver = @receiver.send(*args)
      end
      self
    end
  end

Now, <%= emp.blanker.department.name %> should do what you want.

A few other points:
> <td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
> emp.site.phone.empty?))
>           emp.site.phone
>         else
>           "&nbsp;"
>         end%>
> </td>
activesupport lets you replace (foo.nil? || foo.empty?) with
foo.blank? (I''m assuming you typo''d the logic a bit there...)

That gets us to:

  <td><%=if !emp.site.nil? && !emp.site.phone.blank?
            emp.site.phone
          else
            "&nbsp;"
          end%>
  </td>

As for the ''&nbsp;'' thing, you might like to define an
#or_nbsp method:

  class Object
    def or_nbsp
      str = to_s
      str =~ /\S/ ? str : ''&nbsp;''
    end
  end

Which gets us to:

  <td><%=(emp.site && emp.site.phone).or_nbsp %></td>

Or, combining with the #blanker thing above:

  <td><%=emp.blanker.site.phone.or_nbsp %></td>
> Thanks,
> Jake
Welcome!
George.

[1] http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/17785

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Charly

2007-Feb-11 15:08 UTC

head link

Re: Best way of handling nils in views?

AS a general "good practice" (skinny controller & views, fat
model)
this is more for the Business logic job:
theres a very conveniant function called delegate. Here''s more info
about it :
http://brian.maybeyoureinsane.net/blog/2006/12/15/law-of-demeter-or-how-to-avoid-coding-yourself-into-a-corner-in-rails/

On 11 fév, 11:23, "George Ogata"
<george.og...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> On 2/10/07, Jake Cutter
<cutte...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
>
>
> > I find myself writing ugly code like the following a LOT:
>
> > <td><%=emp.title%></td>
> > <td><%=emp.department.name if !emp.department.nil?
%></td>
> > <td><%=emp.site.name if !emp.site.nil?%></td>
> > <td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
> > emp.site.phone.empty?))
> >           emp.site.phone
> >         else
> >           "&nbsp;"
> >         end%>
> > </td>
>
> > Notice all those nil? checks? Is there no easier or cleaner way of
> > doing this?
>
> Hmm, perhaps one of those "message-eating nils" [1] might have a
place here:
>
>   class Object
>     def blanker
>       Blanker.new(self)
>     end
>   end
>
>   class Blanker
>     instance_methods.each{|name| undef_method(name) unless name =~ /\A__/}
>     def initialize(receiver)
>       @receiver = receiver
>     end
>     def to_s
>       @receiver.to_s
>     end
>     def method_missing(*args)
>       unless @receiver.nil?
>         @receiver = @receiver.send(*args)
>       end
>       self
>     end
>   end
>
> Now, <%= emp.blanker.department.name %> should do what you want.
>
> A few other points:
>
> > <td><%=if (!emp.site.nil? and (!emp.site.phone.nil? or !
> > emp.site.phone.empty?))
> >           emp.site.phone
> >         else
> >           "&nbsp;"
> >         end%>
> > </td>
>
> activesupport lets you replace (foo.nil? || foo.empty?) with
> foo.blank? (I''m assuming you typo''d the logic a bit
there...)
>
> That gets us to:
>
>   <td><%=if !emp.site.nil? && !emp.site.phone.blank?
>             emp.site.phone
>           else
>             "&nbsp;"
>           end%>
>   </td>
>
> As for the ''&nbsp;'' thing, you might like to define
an #or_nbsp method:
>
>   class Object
>     def or_nbsp
>       str = to_s
>       str =~ /\S/ ? str : ''&nbsp;''
>     end
>   end
>
> Which gets us to:
>
>   <td><%=(emp.site && emp.site.phone).or_nbsp
%></td>
>
> Or, combining with the #blanker thing above:
>
>   <td><%=emp.blanker.site.phone.or_nbsp %></td>
>
> > Thanks,
> > Jake
>
> Welcome!
> George.
>
> [1]http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/17785

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

George Ogata

2007-Feb-12 12:10 UTC

head link

Re: Best way of handling nils in views?

On 2/12/07, Charly <charlysisto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> AS a general "good practice" (skinny controller & views, fat
model)
> this is more for the Business logic job:
> theres a very conveniant function called delegate. Here''s more
info
> about it :
>
http://brian.maybeyoureinsane.net/blog/2006/12/15/law-of-demeter-or-how-to-avoid-coding-yourself-into-a-corner-in-rails/
Hi Charly,

Thanks for the link.

Yeah, that''s a good point about Demeter; I guess that''s
another
oft-cited reason to discourage the message-eating-nil thing.
Unfortunately though, #delegate won''t check for nils.  Not that you
couldn''t define your own variant which does easily enough.

George.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Daniel N

2007-Feb-12 22:36 UTC

head link

Re: Best way of handling nils in views?

On 2/12/07, George Ogata
<george.ogata-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
>
> On 2/12/07, Charly
<charlysisto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >
> > AS a general "good practice" (skinny controller & views,
fat model)
> > this is more for the Business logic job:
> > theres a very conveniant function called delegate. Here''s
more info
> > about it :
> >
>
http://brian.maybeyoureinsane.net/blog/2006/12/15/law-of-demeter-or-how-to-avoid-coding-yourself-into-a-corner-in-rails/
>
> Hi Charly,
>
> Thanks for the link.
>
> Yeah, that''s a good point about Demeter; I guess that''s
another
> oft-cited reason to discourage the message-eating-nil thing.
> Unfortunately though, #delegate won''t check for nils.  Not that
you
> couldn''t define your own variant which does easily enough.
>
> George.

This doesn''t sound right in my own ears but I can''t put my
finger on why.
What if the method_missing in Nil was replaced by something like

class Nil

def method_missing( method, *args, &block )
  nil
end

end

This way if there is a nil at any point along the chain at the end it will
be a nil.  Eg, if department is nil, name will also return nil

<%= emp.department.name || "No Department Set" %>

Just a thought, but is there anything wrong with this approach?

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Roland Swingler

2007-Feb-13 09:51 UTC

head link

Re: Best way of handling nils in views?

You could take a look at the Null Object pattern, if appropriate for
your model. I''ve find this quite handy in my RoR apps. A link with an
implementation for active record associations below:

http://blog.craigambrose.com/articles/2006/09/22/active-record-associations-and-the-null-object-pattern

Cheers,
Roland



--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Daniel N

2007-Feb-13 22:54 UTC

head link

Re: Best way of handling nils in views?

On 2/13/07, Roland Swingler
<roland.swingler-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
>
> You could take a look at the Null Object pattern, if appropriate for
> your model. I''ve find this quite handy in my RoR apps. A link with
an
> implementation for active record associations below:
>
>
>
http://blog.craigambrose.com/articles/2006/09/22/active-record-associations-and-the-null-object-pattern
>
> Cheers,
> Roland


Roland,

Thanx for the link, I noticed in the comments that Craig has shown nil
chaining as well but distances himself from it.  This confirms my suspicion
that there may be something wrong with doing this but for the life of me I
don''t know what.

Cheers
Daniel

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

George Ogata

2007-Feb-14 10:09 UTC

head link

Re: Best way of handling nils in views?

On 2/13/07, Daniel N <has.sox-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> On 2/12/07, George Ogata
<george.ogata-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > On 2/12/07, Charly
<charlysisto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >
> > > AS a general "good practice" (skinny controller &
views, fat model)
> > > this is more for the Business logic job:
> > > theres a very conveniant function called delegate.
Here''s more info
> > > about it :
> > >
>
http://brian.maybeyoureinsane.net/blog/2006/12/15/law-of-demeter-or-how-to-avoid-coding-yourself-into-a-corner-in-rails/
> >
> > Hi Charly,
> >
> > Thanks for the link.
> >
> > Yeah, that''s a good point about Demeter; I guess
that''s another
> > oft-cited reason to discourage the message-eating-nil thing.
> > Unfortunately though, #delegate won''t check for nils.  Not
that you
> > couldn''t define your own variant which does easily enough.
> >
> > George.
>
>
>  This doesn''t sound right in my own ears but I can''t put
my finger on why.
> What if the method_missing in Nil was replaced by something like
>
>  class Nil
>
>  def method_missing( method, *args, &block )
>    nil
>  end
>
>  end
>
>  This way if there is a nil at any point along the chain at the end it will
> be a nil.  Eg, if department is nil, name will also return nil
>
>  <%= emp.department.name || "No Department Set" %>
>
>  Just a thought, but is there anything wrong with this approach?
It''s been discussed at length before:

  http://rubyurl.com/S8A

I think the main argument is it can hide errors easily (or make them
harder to track down).  For example, if you typo''d a method name,
it''d
treat it the same as if the attribute was nil.

Regards,
George.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Daniel N

2007-Feb-14 11:32 UTC

head link

Re: Best way of handling nils in views?

On 2/14/07, George Ogata
<george.ogata-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> On 2/13/07, Daniel N
<has.sox-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > On 2/12/07, George Ogata
<george.ogata-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > On 2/12/07, Charly
<charlysisto-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > >
> > > > AS a general "good practice" (skinny controller
& views, fat model)
> > > > this is more for the Business logic job:
> > > > theres a very conveniant function called delegate.
Here''s more info
> > > > about it :
> > > >
> >
http://brian.maybeyoureinsane.net/blog/2006/12/15/law-of-demeter-or-how-to-avoid-coding-yourself-into-a-corner-in-rails/
> > >
> > > Hi Charly,
> > >
> > > Thanks for the link.
> > >
> > > Yeah, that''s a good point about Demeter; I guess
that''s another
> > > oft-cited reason to discourage the message-eating-nil thing.
> > > Unfortunately though, #delegate won''t check for nils. 
Not that you
> > > couldn''t define your own variant which does easily
enough.
> > >
> > > George.
> >
> >
> >  This doesn''t sound right in my own ears but I can''t
put my finger on why.
> > What if the method_missing in Nil was replaced by something like
> >
> >  class Nil
> >
> >  def method_missing( method, *args, &block )
> >    nil
> >  end
> >
> >  end
> >
> >  This way if there is a nil at any point along the chain at the end it
will
> > be a nil.  Eg, if department is nil, name will also return nil
> >
> >  <%= emp.department.name || "No Department Set" %>
> >
> >  Just a thought, but is there anything wrong with this approach?
>
> It''s been discussed at length before:
>
>   http://rubyurl.com/S8A
>
> I think the main argument is it can hide errors easily (or make them
> harder to track down).  For example, if you typo''d a method name,
it''d
> treat it the same as if the attribute was nil.
>
> Regards,
> George.
Thanx for the link.  That was a great thread on the subject.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Jake Cutter

2007-Feb-19 20:15 UTC

head link

Re: Best way of handling nils in views?

On 2/11/07, George Ogata
<george.ogata-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
>   class Object
>     def or_nbsp
>       str = to_s
>       str =~ /\S/ ? str : ''&nbsp;''
>     end
>   end

This works nicely. Thanks George!

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Rails - Feb 2007 - Best way of handling nils in views?

Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?

Re: Best way of handling nils in views?