At the Advanced Rails Studio in Denver 1

Posted by Daniel Wanja Fri, 13 Jun 2008 15:24:51 GMT

We are just starting Day 2. Mike Clark and Chad Fowler are giving the training and are really good at it. They are 24 people taking the training, most not from Denver, and one from Mexico. Right now attendees are not awake and Mike and Chad are trying to wake us up. Yesterday we covered routes, looked at the Rails and Mongrel source code, looked at a RESTful application, covered ActiveResource, and checked ActiveRecord Associations. It’s nice to be able to sit back and take time to play with all these goodies without having to deliver code. It’s a nice refresher for me. Next step will be meta programming.

Here are some notes from the ActiveRecord Associations part of the training:

Join Model: has_many :through

Polymorphic Associations: has_many :address, :as => :addressable

Custom Finders:

class User 
has_many :visits do
     def recent(limiit - 5)
          find(:all, :order => 'created_at DESC', :limit => 5)
     end
end

Active Record Scoping:

with_scope # protected now

before_filter :find_account

Scoped Relationships:

@event.registations.find(params[:id])
@user.events.find_by_id(params[:id])
@event.registations.find(:all, :conditions => "pre_register is true")
Named Associations: 
class Event < ActiveRecord::Base
     has_many :registrations
     has_many :pre_registrations,
                     :class_name => "Registration",
                     :conditions => "pre_register is true"
end

@event.pre_registrations

Named Scope:

class Coupon < ActiveRecord::Base
     named_scope :limit_not_exceeded,   :conditions => "use_count < max_uses"
     named_scope :usable_in_store,        :conditions => "external_only is false"
end

Coupon.limit_not_exceeded
Coupon.usable_in_store
Coupon.limit_not_exceeded.usable_in_store

Dynamic Named Scope:

class Coupon < ActiveRecord::Base
     named_scope :not_expired,  lambda { {  :conditions => ['expires_at > ?', Time.now] } }
     named_scope :used_at_most,   lambda { |uses| {  :conditions => ['use_count <=  ?', uses] } }
end

Coupon.not_expired
Coupon.used_at_most(30)
Coupon.not_expired.used_at_most(10)
Comments

Leave a response

  1. Sebastian Sat, 09 Aug 2008 20:01:12 GMT

    Where can I see this working application?

Comments