This is my first shot at using Rails... How does one establish symmetric
relationships? I''m building a web application where family
relationships between members is useful to know. I''m not sure how to
get the joins to work though...
I have a table of Members and I want to capture, for example, spousal
relationships. The problem I''m running into is that both sides of the
relationship will point back to the ''members'' table, but must
have
different column names.
class CreateRelationships < ActiveRecord::Migration
def self.up
create_table :relationships do |t|
t.column :member_id, :integer
t.column :member2_id, :integer
#preset tags such as "spousal", "parental",
"other"
t.column :type, :string, :limit => 15
#type to be used for "other"
t.column :type_for_other, :string, :limit => 50
end
end
def self.down
drop_table :relationships
end
end
Using a ''has_many :relations, :through => :relationships''
link seems
appropriate, but I''m not sure how to key it to both columns.
class Member < ActiveRecord::Base
has_many :relations, :through => :relationships
end
Is this a job for the :source attribute?
--
Posted via http://www.ruby-forum.com/.
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On 10/8/06, AnalogKid <rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> > > This is my first shot at using Rails... How does one establish symmetric > relationships? I''m building a web application where family > relationships between members is useful to know. I''m not sure how to > get the joins to work though... > > I have a table of Members and I want to capture, for example, spousal > relationships. The problem I''m running into is that both sides of the > relationship will point back to the ''members'' table, but must have > different column names. > > class CreateRelationships < ActiveRecord::Migration > def self.up > create_table :relationships do |t| > t.column :member_id, :integer > t.column :member2_id, :integer > #preset tags such as "spousal", "parental", "other" > t.column :type, :string, :limit => 15 > #type to be used for "other" > t.column :type_for_other, :string, :limit => 50 > end > end > > def self.down > drop_table :relationships > end > end > > > Using a ''has_many :relations, :through => :relationships'' link seems > appropriate, but I''m not sure how to key it to both columns. > > class Member < ActiveRecord::Base > has_many :relations, :through => :relationships > end > > > Is this a job for the :source attribute? > > -- > Posted via http://www.ruby-forum.com/. > > > >I think the proper way of modelling this kind of relationship is to have two entries in the Relationships table. Otherwise, the semantics of the fields change depending on which way you are looking at the relationship. So rather than having mem,ber and member2, you would have relationship_owner and related_person, where your model class should take care of creating both relationship entries in a add_relationship method or similar. This will also make your queries a lot easier. For example, for a father/son relationship, you will have: relationship_owner related_person relationship Daddy Bob Little Joe Son Little Joe Daddy Bob Father When you are querying for everybody who is a son, you only need to look for a "Son" relationship, rather than having endless conditions on (member=some_id and relationship=''Son'') OR (member_2=some_id and relationship=''Father'') Cheers, Max --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
I''m facing a similar problem except that any given individual can have many relationships. For example, Daddy Bob may be Little Joe''s father. At the same time, he might also be Suzy Q''s husband and Little O. Annie''s employer. How would you model that kind of networked relationship? (sorry to hijack this thread, but I''m guessing this is an issue others may have as well.) Max Muermann-3 wrote:> > I think the proper way of modelling this kind of relationship is to have > two > entries in the Relationships table. Otherwise, the semantics of the fields > change depending on which way you are looking at the relationship. > > So rather than having mem,ber and member2, you would have > relationship_owner > and related_person, where your model class should take care of creating > both > relationship entries in a add_relationship method or similar. This will > also > make your queries a lot easier. For example, for a father/son > relationship, > you will have: > > relationship_owner related_person relationship > Daddy Bob Little Joe Son > Little Joe Daddy Bob Father > > When you are querying for everybody who is a son, you only need to look > for > a "Son" relationship, rather than having endless conditions on > (member=some_id and relationship=''Son'') OR (member_2=some_id and > relationship=''Father'') >-- View this message in context: http://www.nabble.com/-newbie--Symmetric-relationships-tf2403812.html#a6711119 Sent from the RubyOnRails Users mailing list archive at Nabble.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 -~----------~----~----~----~------~----~------~--~---
On 10/9/06, s.ross <cwdinfo-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> > > > I''m facing a similar problem except that any given individual can have > many > relationships. For example, Daddy Bob may be Little Joe''s father. At the > same time, he might also be Suzy Q''s husband and Little O. Annie''s > employer. > > How would you model that kind of networked relationship? > > (sorry to hijack this thread, but I''m guessing this is an issue others may > have as well.) > > <snip> > > >This layout for a relationship table models a many-to-many relationship between entries for people. There hsould not be anything else you need to do, except add more rows: relationship_owner related_person relationship Daddy Bob Little Joe Son Little Joe Daddy Bob Father Daddy Bob Annie Wife Annie Daddy Bob Husband Just make sure that your model creteas the appropriate reverse relationship, for example: class Person < ActiveRecord::Base reverse_relationships = [ :Child=>:Parent, :Parent=>:Child, :Husband=>:Wife, :Wife=>Husband, :Employer=>Employee, :Employee=>Employer ] def relate_to(person, relationship) r1 = Relationship.create do |r| r.owner = this r.related_person = person r.relationship = relationship end r2 = Relationship.create do |r| r.owner = person r.related_person = this r.relationship = reverse_relationships[relationship.intern].to_s end end end Note that this does not make a distinction between Son/Daughter or Mother/Father. If you have your has_many :through set up right, you can then use Person.find(1).relationships. You can even use association extensions: has_many :related_people, :through=>:relationship do def relation(type_of_relationship) find(:all, :conditions=>[ ''relationship_type=?'', type_of_relationship ] end end You can then do: dad = Person.find(1) children = dad.related_people.relation(''Child'') As the association extension automatically sets the scope to the parent relationship (parent and relationship here are in relational database terms). Cheers, Max --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---