Hello,
Is it possible to initialize model attributes from a SQL select
element that''s not backed by a real database column?
For example:
class A << ActiveRecord::Base
attr_accessor :state_info #Not a db column
has_many :b, :finder_sql=''SELECT b.*,
\''#{state_info}\'' as
state_info FROM b WHERE b.a_id = #{id}''
end
class B << ActiveRecord::Base
attr_accessor :state_info #Not a db column
belongs_to :a
end
a.state_info = "test"
b = a.b.first
#b.state_info is nil, but I want it to be initialized to "test" when
it''s returned from the :finder_sql.
I don''t think I can accomplish this with an after_find/
after_initialize callback either, since I need to have access to the
value of a.state_info in order to set b.state_info.
Thanks,
Tom
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On 2 Dec 2007, at 04:18, tom_302 wrote:> > Hello, > > Is it possible to initialize model attributes from a SQL select > element that''s not backed by a real database column? > > For example: > > class A << ActiveRecord::Base > attr_accessor :state_info #Not a db column > has_many :b, :finder_sql=''SELECT b.*, \''#{state_info}\'' as > state_info FROM b WHERE b.a_id = #{id}'' > end > > class B << ActiveRecord::Base > attr_accessor :state_info #Not a db column > belongs_to :a > end > > a.state_info = "test" > b = a.b.first > #b.state_info is nil, but I want it to be initialized to "test" when > it''s returned from the :finder_sql.I''m assuming that :finder_sql='' is a typo for :finder_sql=>'' In activerecord any column in the sql result ends up being accessible. In this case the attr_accessor you''ve got on B is actually clobbering the state_info column. Fred> > > I don''t think I can accomplish this with an after_find/ > after_initialize callback either, since I need to have access to the > value of a.state_info in order to set b.state_info. > > Thanks, > Tom > > > >--~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
Thanks Fred, The problem is that I need a transient variable on the models (e.g. attr_accessor :state_info). There are other models, A, B, C, D,... chained together by foreign key, and transient :state_info. I need to use the value of :state_info as criteria in the finder_sql in each link of the chain. So, the chain is traversed differently depending on how the root object''s state_info is initialized. Is there any way to keep the attr_accessor on the models and also load the select-element into it with finder_sql? On Dec 2, 5:49 am, Frederick Cheung <frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 2 Dec 2007, at 04:18, tom_302 wrote: > > > > > > > Hello, > > > Is it possible to initialize model attributes from a SQL select > > element that''s not backed by a real database column? > > > For example: > > > class A << ActiveRecord::Base > > attr_accessor :state_info #Not a db column > > has_many :b, :finder_sql=''SELECT b.*, \''#{state_info}\'' as > > state_info FROM b WHERE b.a_id = #{id}'' > > end > > > class B << ActiveRecord::Base > > attr_accessor :state_info #Not a db column > > belongs_to :a > > end > > > a.state_info = "test" > > b = a.b.first > > #b.state_info is nil, but I want it to be initialized to "test" when > > it''s returned from the :finder_sql. > > I''m assuming that :finder_sql='' is a typo for :finder_sql=>'' > In activerecord any column in the sql result ends up being accessible. > In this case the attr_accessor you''ve got on B is actually clobbering > the state_info column. > > Fred > > > > > I don''t think I can accomplish this with an after_find/ > > after_initialize callback either, since I need to have access to the > > value of a.state_info in order to set b.state_info. > > > Thanks, > > Tom--~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---