There really doesn''t seem to be a *declarative* way to define a default
value for belongs_to and has_one associations
class Person < ActiveRecord::Base
belongs_to :address
end
p = Person.new
p.address.city = ''Atlantis'' # Bummer!
Of course, there''s an easy way to avoid this
class Person < ActiveRecord::Base
belongs_to :address
def after_initialize
self.address ||= Address.new
end
end
It just doesn''t feel right. What I''d rather write is this
class Person < ActiveRecord::Base
belongs_to :address, :default => true
end
and alternatively
class Person < ActiveRecord::Base
belongs_to :address,
:default => proc { |record| record.address ||= Address.new }
end
Are there any reasons why ActiveRecord should *not* do something like
this?
Michael
--
Michael Schuerig
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org
http://www.schuerig.de/michael/
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Sounds logical. The only concern I''d have is that it would be ''implicit'' and so you wouldn''t know whether using person.address was its ''existing'' address or its ''auto-magically created'' address. Leaving it explicit helps you have more understanding of which is new, which isn''t.> It just doesn''t feel right. What I''d rather write is this > > class Person < ActiveRecord::Base > belongs_to :address, :default => true > endThat would be reasonable, though I''d probably not use it as I for some reason love explicitness :) -R -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
> There really doesn''t seem to be a *declarative* way to define a default > value for belongs_to and has_one associationsran into this, if useful. http://gilesbowkett.blogspot.com/2007/12/snazzy-resource.html --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
On Tue, Apr 29, 2008 at 4:26 PM, Michael Schuerig <michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org> wrote:> > > There really doesn''t seem to be a *declarative* way to define a default > value for belongs_to and has_one associations > > class Person < ActiveRecord::Base > belongs_to :address > end > > p = Person.new > p.address.city = ''Atlantis'' # Bummer!Hmm, I sniff the code smell of a violation of the /law|strong suggestion/ of Demeter here. Better to define a city= method on Person (if this is what you really want) which hides the implementation.> Of course, there''s an easy way to avoid this > > class Person < ActiveRecord::Base > belongs_to :address > > def after_initialize > self.address ||= Address.new > end > end > > It just doesn''t feel right. What I''d rather write is this > > class Person < ActiveRecord::Base > belongs_to :address, :default => true > end > > and alternatively > > class Person < ActiveRecord::Base > belongs_to :address, > :default => proc { |record| record.address ||= Address.new } > end > > Are there any reasons why ActiveRecord should *not* do something like > this?Well, I have to ask, presumably Person belongs_to Address (rather than the other way around) because more than one person can have the same Address. The normal relationship on the other side of belongs_to is has_many. Whenever I see has_one (unless it uses :conditions/:order or the like to pick out one of a has_many) I wonder why the two models aren''t combined, either directly or via STI. -- Rick DeNatale My blog on Ruby http://talklikeaduck.denhaven2.com/ --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
On Wednesday 30 April 2008, Rick DeNatale wrote:> On Tue, Apr 29, 2008 at 4:26 PM, Michael Schuerig<michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org> wrote:> > There really doesn''t seem to be a *declarative* way to define a > > default value for belongs_to and has_one associations > > > > class Person < ActiveRecord::Base > > belongs_to :address > > end > > > > p = Person.new > > p.address.city = ''Atlantis'' # Bummer! > > Hmm, I sniff the code smell of a violation of the /law|strong > suggestion/ of Demeter here.I don''t. That law doesn''t say only a single dot is allowed, does it? Apart from being called a law, I''d like to see exactly what improvement following that rule would effect in this particular case. In my rails code I very rarely have assignments like the one above. What I do have is views and particularly forms where I show and edit objects and related objects, such as a person and their address. Partials lend themselves to this and in such a case, I want to pass a valid object, say an address, into the partial. In a sense I''m even following the Law of Demeter in that way. Anyway, whenever person.address gets passed into the address partial, I want it to be initialized with an appropriate address object.> Better to define a city= method on Person (if this is what you really > want) which hides the implementation.Even if I did that -- which I won''t without positive indication --, it would not remove the original problem. As a negative indication I''d like to point out that adding #city=, #zip= etc. to Person dilutes the responsibility of that model class. These attributes belong on an Address model class. Now, if we take presenters into consideration, there I''d be inclined to put all relevant accessors directly on the presenter. But at any rate, that wouldn''t touch the original issue. Michael -- Michael Schuerig mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org http://www.schuerig.de/michael/ --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---