Wolfram Arnold www.rubyfocus.biz Nested Attributes CRUD on multiple models without crud

CRUD

on multiple models

without crud

Associations class Pirate < ActiveRecord::Base has_one :ship end class Ship < ActiveRecord::Base belongs_to :pirate end

class Pirate < ActiveRecord::Base has_one :ship end

class Ship < ActiveRecord::Base belongs_to :pirate end

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

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

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

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

Demo

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

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

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

: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

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

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

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

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

Wolfram Arnold www.rubyfocus.biz Thank you!

Thank you!