I have read many articles about polymorphic associations in Rails and also about plugins for this purpose (mainly the has_many_polymorphs plugin). Unfortunately, I am still unsure how to solve my problem: Let''s say you have these models you want to set in relation to each other: Person, Document, Realty. You want to link polymorphic objects with each other. Let''s call the "join-class" Relationship. A Relationship has a name and at least two link-partners. A Relationship between Person and Document could be called "Creator". A Relationship between a Person and a Realty would have the name "Owner". A Relationship between a Document and a Realty would have the name "Lease". So, how to implement this idea, and to be able to easly extend the list of linkable objects? Is it possible to avoid any association-definitions in the linkable models? Thank you for your help, Reiner -- 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 -~----------~----~----~----~------~----~------~--~---
Reiner, I don''t believe you have the need for polymorphic associations in the above example as you have a seperate association "type" already specced out for each relation class Person < ActiveRecord::Base has_many :documents has_many :realties end class Document < ActiveRecord::Base belongs_to :owner, class_name => "Person" belongs_to :realty end class Realty < ActiveRecord::Base belongs_to :owner, class_name => "Person" has_many :leases, class_name => "Document" end Where do you need polymorphic associations in the above example? p.s. I know next to nothing about real estate so please forgive me if I got your relation wrong between documents and realties.. does a realty have many leases or is it the other way around?? :) hth ilan> > So, how to implement this idea, and to be able to easly extend the list > of linkable objects? Is it possible to avoid any association-definitions > in the linkable models? > > Thank you for your help, > > > Reiner-- 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 -~----------~----~----~----~------~----~------~--~---
Hi Ilan, thank you for your answer: Ilan Berci wrote:> class Person < ActiveRecord::Base > has_many :documents > has_many :realties > end > > class Document < ActiveRecord::Base > belongs_to :owner, class_name => "Person" > belongs_to :realty > end > > class Realty < ActiveRecord::Base > belongs_to :owner, class_name => "Person" > has_many :leases, class_name => "Document" > end >Well, this is exacly what I want to avoid. As the project grows, more and more classes can be linked to each other. With your approach, each class would start with a listing of "hard-wired" associations. Imagine 10 classes being able to be linked to each other - what a mess to maintain in each class! Instead, I would like something like this: class Relationship < ActiveRecord::Base has_one :the_one # can be any model has_one :the_other # can be any model end or, even more flexible class Relationship < ActiveRecord::Base has_many :members # a list model of any type end But how to do this with "the magic" of Rails? -- 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 -~----------~----~----~----~------~----~------~--~---
Reiner, My suggestion then is to come up with your classes first and then make a design. A very common pitfall is to design for something that "may" happen and then later face over engineered code.. In the late nineties, we called this the YAGNI principle which stood for "You Aint Going to Need It!" If you propose your new more complete class model, I can help with your polymorphic associations (If you still need them).. Lastly, remember that PAs are not free, they add extra conditions to the select clauses which can be quite costly with improper or imcomplete indexing. Reiner Pittinger wrote:> > But how to do this with "the magic" of Rails?-- 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 -~----------~----~----~----~------~----~------~--~---
Dear Ilan,
although I just supplied just three basic models, my application already
contains more than 15 different models that should be linked to each
other.
Some more examples:
- I need a relationship between two documents ("Like: Document B is an
attachment to Document A).
- I need a relationship beween a Key-Class (the ones you use to open a
house ;) and a RealtyItem (name: "Key House-Entrance").
- I need a relationship between two Persons, to model something like
"Assistent"
I could supply a dozen more. This is why already now I want a flexible
modelling of these relationships.
I image a table to store the relationships like this:
id name the_one_id the_one_class the_other_id the_other_class
1 Owner 2 Person 3 RealtyItem
2 Assistant 5 Person 5 Person
3 Lease#333 5 Document 3 RealtyItem
It seems so simple - but how do I achieve it correctly using Rails?
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Search for "Rails double polymorphic" in Google... http://wiki.rubyonrails.org/rails/pages/ManytoManyPolymorphicAssociations http://blog.evanweaver.com/files/doc/fauna/has_many_polymorphs/files/README.html or just assume that everyone else will do the googling for you... -- 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 -~----------~----~----~----~------~----~------~--~---
I came to the solution using the has_many_polymorphs plugins:
The correct modelling is:
class Relationship < ActiveRecord::Base
belongs_to :relationship_owner, :polymorphic => true
belongs_to :relationship_partner, :polymorphic => true
acts_as_double_polymorphic_join(
:relationship_owners =>[:people, :realties, :documents],
:relationship_partners => [:people, :realties, :documents]
)
end
... and the migration:
class CreateRelationships < ActiveRecord::Migration
def self.up
create_table :relationships do |t|
t.string :name
t.references :relationship_owner, :polymorphic => true
t.references :relationship_partner, :polymorphic => true
t.timestamps
end
end
def self.down
drop_table :relationships
end
end
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