I''d like the change the order field in a has_many relationship based on
the value of one of my other fields. Is this possible?
In this case my parent model is Quiz and the child is QuizQuestion. If
a quiz''s ''style'' attribute is set to
''sequential'' i''d like to get
@quiz.questions back in order of quiz_questions.position, otherwise i''d
like to get them back in order of quiz_questions.low_band.
So, something like the following (i know this doesn''t work because self
is the class here)
has_many :quiz_questions, :order => "#{self[:style] == sequential ?
''position'' : ''low_band''}"
can i use a proc to set the order for example?
thanks, max
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On Feb 23, 7:17 pm, Max Williams <li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> I''d like the change the order field in a has_many relationship based on > the value of one of my other fields. Is this possible? > > In this case my parent model is Quiz and the child is QuizQuestion. If > a quiz''s ''style'' attribute is set to ''sequential'' i''d like to get > @quiz.questions back in order of quiz_questions.position, otherwise i''d > like to get them back in order of quiz_questions.low_band. > > So, something like the following (i know this doesn''t work because self > is the class here) > > has_many :quiz_questions, :order => "#{self[:style] == sequential ? > ''position'' : ''low_band''}" >The order clause is an sql fragment, so you can''t do quite what you''ve written. You can of course write an if statement in sql (although you would have to also join the parent table), and order by something like IF(foo = ''bar'', position, low_band) This wouldn''t end up as a very efficient query though and feels quite nasty. Fred> can i use a proc to set the order for example? > > thanks, max > -- > Posted viahttp://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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@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.
Frederick Cheung wrote:> On Feb 23, 7:17�pm, Max Williams <li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote: >> >> has_many :quiz_questions, :order => "#{self[:style] == sequential ? >> ''position'' : ''low_band''}" >> > > The order clause is an sql fragment, so you can''t do quite what you''ve > written. > You can of course write an if statement in sql (although you would > have to also join the parent table), and order by something like > IF(foo = ''bar'', position, low_band) > > This wouldn''t end up as a very efficient query though and feels quite > nasty. > > > Fredyeah, i''m inclined to agree re the nasty. It does work though: in case anyone else stumbles across this, i have has_many :quiz_questions, :dependent => :destroy, :include => [:quiz], :order => "IF(quizzes.style = ''sequential'', position, low_band)" The extra include is the dodgy bit isn''t it. I''ll give it a go anyway. Thanks! -- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@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.