Actuve Record
in [Ruby]
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From: Rajkumar Surabhi on 25 Mar 2010 07:19 HI all in my application , i have 2 tables subjects and teachers. the relation is one to many. i have to display the subjects first and when i click on the subjects i have to display the teachers. and i have to add the new teacher to the teachers table by selecting the subject. how to do this -- Posted via http://www.ruby-forum.com/.
From: Josh Cheek on 25 Mar 2010 13:43 [Note: parts of this message were removed to make it a legal post.] On Thu, Mar 25, 2010 at 5:19 AM, Rajkumar Surabhi <mailtorajuit(a)gmail.com>wrote: > HI all > > in my application , i have 2 tables subjects and teachers. the relation > is one to many. > > i have to display the subjects first and when i click on the subjects i > have to display the teachers. > > and i have to add the new teacher to the teachers table by selecting the > subject. > > how to do this > -- > Posted via http://www.ruby-forum.com/. > > Hi, Rajkumar, this is the Ruby mailing list, you probably want the Ruby on Rails list at http://groups.google.com/group/rubyonrails-talk The associations guide at http://guides.rubyonrails.org/association_basics.html talks about what you are asking. The short answer is that subjects will have a foreign key of the teachers, and in your model you say "belongs_to :teacher" and in your teacher model you say "has_many :subjects" Then from a subject, you can get it's teacher with subject.teacher and from a teacher you can get it's subjects with teacher.subjects. To link them up, just use the setters. subject.teacher = current_teacher. You should consider, though, whether this design is really appropriate. At my university, a subject may be taught by multiple teachers. For example, there are usually between 5 and 10 calculus courses, each one taught by a different teacher. You may want to add a courses table, where each course belongs to one subject, and one teacher, and then you can have a many to many relationship between subjects and teachers, through the courses. That should all be talked about on the guide I linked you to, but really the Rails ML is where you should ask future questions about ActiveRecord.
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