Ruby on Rails - Modelos
Criação de modelo
Model.new # creates a new empty model
Model.create( :field ⇒ 'value', :other_field ⇒ 42 )
# creates an object with the passed parameters and saves it
Model.find_or_create_by_field( value )
# searches for a record where "field = value", creates
# a new record if not found
User.find_or_create_by_name_and_email( 'ramjoe', '[email protected]')
Relações de modelo
Existem quatro maneiras de associar modelos. has_one, has_many, belongs_to e has_and_belongs_to_many. Supondo as seguintes quatro entidades -
def Order < ActiveRecord::Base
has_many :line_items
belongs_to :customer
end
def LineItem < ActiveRecord::Base
belongs_to :order
end
def Customer < ActiveRecord::Base
has_many :orders
has_one :address
end
def Address < ActiveRecord::Base
belongs_to :customer
end
Considere o seguinte relacionamento -
def Category < ActiveRecord::Base
has_and_belongs_to_many :products
end
def Product < ActiveRecord::Base
has_and_belongs_to_many :categories
end
Modelos de associação de associação
Considere o seguinte relacionamento agora. Isso descreve como podemos usar junções ao definir o relacionamento.
class Author < ActiveRecord::Base
has_many :authorships
has_many :books, :through ⇒ :authorships
end
class Authorship < ActiveRecord::Base
belongs_to :author
belongs_to :book
end
class Book < ActiveRecord::Base
has_one :authorship
end
@author = Author.find :first
# selects all books that the author's authorships belong to.
@author.authorships.collect { |a| a.book }
selects all books by using the Authorship join model
@author.books
Verifique Associações para mais detalhes.
rails-reference-guide.htm