2009 07 21: Nested Attributes
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The document discusses implementing nested attributes in Ruby on Rails for managing associations between models, specifically a 'Pirate' model and a 'Ship' model. It highlights the importance of handling validations and saving processes in the model rather than in the controller, emphasizing the use of the 'autosave' feature in Rails 2.3. Additionally, it advises against creating separate APIs for related objects and provides references for further exploration of common practices in Rails.
![User Interface? Form with pirate and ship fields form_for :pirate do |pf| pf.text_field :catchphrase pf.fields_for :ship do |sf| sf.text_field :name end # params[pirate][ship] # Note: broken! end](https://image.slidesharecdn.com/2009-07-21-wanestedattributes-090722014949-phpapp01/85/2009-07-21-Nested-Attributes-3-320.jpg)
![Controller Interface? def create @pirate = Pirate.new(params[:pirate]) @ship = Ship.new(params[:pirate][:ship]) @ship.pirate = @pirate if @pirate.save && @ship.save ... else # what about rollback? end end](https://image.slidesharecdn.com/2009-07-21-wanestedattributes-090722014949-phpapp01/85/2009-07-21-Nested-Attributes-4-320.jpg)
2009 07 21: Nested Attributes
- 1. Wolfram Arnold www.rubyfocus.biz Nested Attributes CRUD on multiple models without crud
- 2. Associations class Pirate < ActiveRecord::Base has_one :ship end class Ship < ActiveRecord::Base belongs_to :pirate end
- 3. User Interface? Form with pirate and ship fields form_for :pirate do |pf| pf.text_field :catchphrase pf.fields_for :ship do |sf| sf.text_field :name end # params[pirate][ship] # Note: broken! end
- 4. Controller Interface? def create @pirate = Pirate.new(params[:pirate]) @ship = Ship.new(params[:pirate][:ship]) @ship.pirate = @pirate if @pirate.save && @ship.save ... else # what about rollback? end end
- 5. Demo
- 6. Fat model/skinny controller Logic in the model, not views/controllers Assignments class Pirate < ActiveRecord::Base def ship_attributes=(attrs) ... end end Validations handled in model, incl. child models
- 7. Saving—when? :autosave => true flag, new in Rails 2.3! Automatically turned on for accepts_nested_attributes_for Parent will save all children New parent, modified children Existing parent, new/modified children As a transaction—rollback on validation failure Cascaded error messages Removes a lot of confusion Demo
- 8. Web Service API PirateController and ShipController? Not advised if Objects have a relationship, e.g. has_one association Dependencies Business logic rules/validations Better single API with nested attributes Simpler client code Less network traffic
- 9. References http://api.rubyonrails.org/classes/ActiveRecord/NestedAttributes/ClassMethods.html#M002132 http://github.com/h-lame/parental_control http://railscasts.com/episodes/75-complex-forms-part-3 Advanced Rails Recipes, Pragmatic Programmer Series
- 10. Wolfram Arnold www.rubyfocus.biz Thank you!