Rails - Sep 2009 - Basic Rails problem with has_many nil values and permalinks

Hi,

I have a model property with has_many.  I find the property and then I
need to find the name of the building or the neighborhood that the
property belongs to.  The property is not always assigned a building or
neighborhood.

This becomes a problem when createing permalinks with permalink_fu.

has_permalink [:neighborhood_name, :building_name, :address]

The neighborhood name and building name are defined here in property.rb

  def neighborhood_name
      neighborhood.name
  end

  def building_name
       building.name
  end

If the property does not have a neighborhood or a building, then I get
an error:
The error occurred while evaluating nil.name):
  app/models/property.rb:425:in `neighborhood_name''


I know that I''m missing something really basic in Rails.  Can someone
help me out so that it generates the permalink even if the neighborhood
or building are empty?

Thanks.
-- 
Posted via http://www.ruby-forum.com/.

2009/9/28 Cs Webgrl
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>
> Hi,
>
> I have a model property with has_many.  I find the property and then I
> need to find the name of the building or the neighborhood that the
> property belongs to.  The property is not always assigned a building or
> neighborhood.
>
> This becomes a problem when createing permalinks with permalink_fu.
>
> has_permalink [:neighborhood_name, :building_name, :address]
>
> The neighborhood name and building name are defined here in property.rb
>
>  def neighborhood_name
>      neighborhood.name
>  end
>
>  def building_name
>       building.name
>  end
>
> If the property does not have a neighborhood or a building, then I get
> an error:
> The error occurred while evaluating nil.name):
>  app/models/property.rb:425:in `neighborhood_name''
>
>
> I know that I''m missing something really basic in Rails.  Can
someone
> help me out so that it generates the permalink even if the neighborhood
> or building are empty?
>
You could just test neighborhood and building in your _name methods
and return an appropriate default if nil.

Colin

Colin Law wrote:
> You could just test neighborhood and building in your _name methods
> and return an appropriate default if nil.

Thanks for your reply.  I don''t mean to make you do all of the work,
but
I can''t seem to find the correct syntax to go with this to make it pass
correctly?  Everything I put into the _name methods is ignored and I 
still get an error.

Thanks for your help.

-- 
Posted via http://www.ruby-forum.com/.

Cs Webgrl wrote:
> Colin Law wrote:
> 
>> You could just test neighborhood and building in your _name methods
>> and return an appropriate default if nil.
> 
> 
> Thanks for your reply.  I don''t mean to make you do all of the
work, but
> I can''t seem to find the correct syntax to go with this to make it
pass
> correctly?  Everything I put into the _name methods is ignored and I 
> still get an error.
What are you putting into those methods?  Instead of asking for our 
code, show us yours.
> 
> Thanks for your help.
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

2009/9/28 Cs Webgrl
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>
> Colin Law wrote:
>
>> You could just test neighborhood and building in your _name methods
>> and return an appropriate default if nil.
>
>
> Thanks for your reply.  I don''t mean to make you do all of the
work, but
> I can''t seem to find the correct syntax to go with this to make it
pass
> correctly?  Everything I put into the _name methods is ignored and I
> still get an error.
You have snipped the original.
I don''t know whether has_permalink is happy with nil parameters, if so
then you could just do

def neighborhood_name
     neighborhood.name if neighborhood
end

This will return nil if neighborhood is nil.
If you need a default name however then something like

def neighborhood_name
     neighborhood ? neighborhood.name : ''default_name''
end

If Marnen reads this he will tell you (and probably me) in no
uncertain terms to read up on basic Ruby coding :)

Colin

Colin Law wrote:
> 2009/9/28 Cs Webgrl
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>> still get an error.
> You have snipped the original.
> I don''t know whether has_permalink is happy with nil parameters,
if so
> then you could just do
> 
> def neighborhood_name
>      neighborhood.name if neighborhood
> end
> 
> This will return nil if neighborhood is nil.
> If you need a default name however then something like
> 
> def neighborhood_name
>      neighborhood ? neighborhood.name : ''default_name''
> end
Yeah, that''s about what I was thinking.
> 
> If Marnen reads this he will tell you (and probably me) in no
> uncertain terms to read up on basic Ruby coding :)
Good God, am I becoming a List Personality [TM]? :)

You''re right, I''d recommend that the OP brush up on basic
Ruby. For you,
I''d simply recommend not spoon-feeding...
> 
> Colin
Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

2009/9/28 Marnen Laibow-Koser
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>:
>
> Colin Law wrote:
>
>>
>> If Marnen reads this he will tell you (and probably me) in no
>> uncertain terms to read up on basic Ruby coding :)
>
> Good God, am I becoming a List Personality [TM]? :)
>
> You''re right, I''d recommend that the OP brush up on basic
Ruby. For you,
> I''d simply recommend not spoon-feeding...
>
I think sometimes a modicum of spoon feeding is helpful to get people
over immediate problems, this combined with hints as to where to go
next.  In this case I bounced the hint off you so I looked like the
nice guy :)

Somehow this thread seems to have got split, for me anyway.  Your
replies are appearing on a different thread to the original.

Colin

Colin Law wrote:
> 
> I think sometimes a modicum of spoon feeding is helpful to get people
> over immediate problems, this combined with hints as to where to go
> next.  In this case I bounced the hint off you so I looked like the
> nice guy :)

Thank you for the information.  Yes, I need to read up on some basic 
Ruby.  I was thinking that I needed to do neighborhood.<something> and 
not just neighborhood which is why I was unsuccessful.  Back to reading. 
I have the David Black''s Ruby for Rails book along with the Pick axe 
book and AWD.  If there''s another resource that you recommend, please 
let me know.
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