Agile Web Development

Use-case:

Family and Person have some properties like Car, DVD, Book. They can own these or borrow from someone else, one silly restriction is Family can borrow Car, Person can't.

Here the solution:

class Family < ActiveRecord
polymorphically_has_many :items, :from => [:cars, :dvds, :books]
polymorphically_has :borrowed, :many => items, :from => [:cars, :dvds, :books]
end

class Person < ActiveRecord
polymorphically_has_many :ownables, :from => [:cars, :dvds, :books]
polymorphically_has :borrowed, :many => items, :from => [:dvds, :books]
end

class Book < ActiveRecord
polymorphically_has_one :owner, :through => ownables
polymorphically_has_one :borrower, :through => borrowed_items
end

And now

p = Person.create
p.ownables
p.ownables.dvds
p.ownables.cars
p.ownables.books
p.borrowed_items
p.borrowed_items.dvds

and pretty much the same for Family, and we also have

b = Book.find(:first)
b.onwer
b.borrower

Look at http://github.com/ducduong/polymorphic_association/tree/master for more details

Owner: Duc Duong

Home: http://github.com/ducduong/polymorphic_association/tree/master

Repository: git://github.com/ducduong/polymorphic_association.git

License: Rails' (MIT)

Category: Model