Hi, I have a fairly typical has_many, through setup with a bit of a twist. class Course < ActiveRecord::Base has_many :placements has_many :students, :through => :placements end class Student < ActiveRecord::Base has_many :placements has_many :courses, :through => :placements end class Placements < ActiveRecord::Base belongs_to :course belongs_to :student end So with this I could grab all the students for a course by: @students = @course.students Everything is fine so far, but here is the twist. I have to narrow things down by some data on the placements table. Let''s say I have a column called "placed_by" on "Placements" How would I retrieve all of the students for a course if I only wanted to see those who were placed by "Bob" for example? --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
two possible ways:
1) if the condition has to be met every time:
has_many :students, :through => :placements, :conditions => {:placed_on
=> ''you_value''}
2) more likely and more flexible the "association extensions":
has_many :students, :through => :placements do
def placed_by(who)
find_all_by_placed_by(who)
end
end
can be called:
@students = @course.students.placed_by(who_id)
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Thanks, #2 nails it! Would it be roughly the same if there were two or three unrelated fields on there? Something like: has_many :students, :through => :placements do def find_by(who, when) find(:all, :conditions =>[''placed_by = ?, created_on >= ?'',who, when]) end end @students = @course.students.find_by(who_id, datetime) On Dec 3, 2007 1:53 PM, Thorsten Mueller <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > two possible ways: > > 1) if the condition has to be met every time: > > has_many :students, :through => :placements, :conditions => {:placed_on > => ''you_value''} > > 2) more likely and more flexible the "association extensions": > > has_many :students, :through => :placements do > def placed_by(who) > find_all_by_placed_by(who) > end > end > > can be called: > @students = @course.students.placed_by(who_id) > -- > 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 -~----------~----~----~----~------~----~------~--~---
Joe Cairns wrote:> Thanks, #2 nails it! Would it be roughly the same if there were two or > three unrelated fields on there? Something like: > > has_many :students, :through => :placements do > def find_by(who, when) > find(:all, :conditions =>[''placed_by = ?, created_on >= ?'',who, > when]) > end > end > > @students = @course.students.find_by(who_id, datetime) > > On Dec 3, 2007 1:53 PM, Thorsten Mueller > <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>yes, you can place any code you like in this method, as long as it returns something that''s usable as a student (in this case) ;) you can use the finder functions or find_by_sql for really hard work in theory it should even be possible to return an array of hashes, that contain all the necessary columns as keys [{name => "student1", :location => "Washington" ...}, {:name => "student two", ...}] but i never tried that last one myself -- 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 -~----------~----~----~----~------~----~------~--~---
What about something a little different? Is there a way to process 2 levels deep? so @all_courses = @students.courses In SQL that could be an IN() statement composed of student IDs. On Dec 3, 2:27 pm, Thorsten Mueller <rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> Joe Cairns wrote: > > Thanks, #2 nails it! Would it be roughly the same if there were two or > > three unrelated fields on there? Something like: > > > has_many :students, :through => :placements do > > def find_by(who, when) > > find(:all, :conditions =>[''placed_by = ?, created_on >= ?'',who, > > when]) > > end > > end > > > @students = @course.students.find_by(who_id, datetime) > > > On Dec 3, 2007 1:53 PM, Thorsten Mueller > > <rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> > > yes, you can place any code you like in this method, as long as it > returns something that''s usable as a student (in this case) ;) > > you can use the finder functions or find_by_sql for really hard work > in theory it should even be possible to return an array of hashes, that > contain all the necessary columns as keys > [{name => "student1", :location => "Washington" ...}, {:name => "student > two", ...}] > but i never tried that last one myself > -- > 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-/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 -~----------~----~----~----~------~----~------~--~---