284 lines
7.3 KiB
Markdown
284 lines
7.3 KiB
Markdown
title: Rails Models
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----
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### Generating models
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$ rails g model User
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### Associations
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belongs_to
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has_one
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has_many
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has_many :through
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has_one :through
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has_and_belongs_to_many
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### Has many
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belongs_to :parent, :foreign_key => 'parent_id' class_name: 'Folder'
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has_many :folders, :foreign_key => 'parent_id', class_name: 'Folder'
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has_many :comments, :order => "posted_on"
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has_many :comments, :include => :author
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has_many :people, :class_name => "Person"
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has_many :people, :conditions => "deleted = 0"
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has_many :tracks, :order => "position"
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has_many :comments, :dependent => :nullify
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has_many :comments, :dependent => :destroy
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has_many :tags, :as => :taggable
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has_many :reports, :readonly => true
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has_many :subscribers, :through => :subscriptions, class_name: "User", :source => :user
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has_many :subscribers, :finder_sql =>
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'SELECT DISTINCT people.* ' +
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'FROM people p, post_subscriptions ps ' +
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'WHERE ps.post_id = #{id} AND ps.person_id = p.id ' +
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'ORDER BY p.first_name'
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### belongs to
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belongs_to :author,
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:dependent => :destroy # or :delete
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:class_name => "Person"
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:select => "*"
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:counter_cache => true
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:counter_cache => :custom_counter
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:include => "Book"
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:readonly => true
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:conditions => 'published = true'
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:touch => true
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:touch => :authors_last_updated_at
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:primary_key => "name"
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:foreign_key => "author_name"
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### Many-to-many
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If you have a join model:
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class Programmer < ActiveRecord::Base
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has_many :assignments
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has_many :projects, :through => :assignments
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end
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class Project < ActiveRecord::Base
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has_many :assignments
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has_many :programmers, :through => :assignments
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end
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class Assignment
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belongs_to :project
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belongs_to :programmer
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end
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Or HABTM:
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has_and_belongs_to_many :projects
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has_and_belongs_to_many :projects, :include => [ :milestones, :manager ]
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has_and_belongs_to_many :nations, :class_name => "Country"
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has_and_belongs_to_many :categories, :join_table => "prods_cats"
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has_and_belongs_to_many :categories, :readonly => true
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has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :delete_sql =>
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"DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}"
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### Polymorphic associations
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class Post
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has_many :attachments, :as => :parent
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end
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class Image
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belongs_to :parent, :polymorphic => true
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end
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And in migrations:
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create_table :images do
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t.references :post, :polymorphic => true
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end
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### Dynamic attribute-based finders
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# Returns one record
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Person.find_by_name(name)
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Person.find_last_by_name(name)
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Person.find_or_create_by_name(name)
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Person.find_or_initialize_by_name(name)
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# Returns a list of recordns
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Person.find_all_by_name(name)
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# Add a bang to make it raise an exception
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Person.find_by_name!(name)
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# You may use `scoped` instead of `find`
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Person.scoped_by_user_name
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Validation
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----------
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class Person < ActiveRecord::Base
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# Non empty
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validates :name, :presence => true
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# Checkboxes
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validates :terms_of_service, :acceptance => true
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# Validate the associated records to ensure they're valid as well
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has_many :books
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validates_associated :books
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# Confirmation (like passwords)
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validates :email, :confirmation => true
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# Unique
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validates :slug, :uniqueness => true
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validates :slug, :uniqueness => { :case_sensitive => false }
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validates :holiday, :uniqueness => { :scope => :year, :message => "only once a year" }
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# Format
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validates :legacy_code, :format => {
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:with => /\A[a-zA-Z]+\z/,
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:message => "Only letters allowed"
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}
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# Length
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validates :name, :length => { :minimum => 2 }
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validates :bio, :length => { :maximum => 500 }
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validates :password, :length => { :in => 6..20 }
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validates :number, :length => { :is => 6 }
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# Length (full enchalada)
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validates :content, :length => {
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:minimum => 300,
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:maximum => 400,
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:tokenizer => lambda { |str| str.scan(/\w+/) },
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:too_short => "must have at least %{count} words",
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:too_long => "must have at most %{count} words"
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}
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end
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# Numeric
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validates :points, :numericality => true
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validates :games_played, :numericality => { :only_integer => true }
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# Multiple
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validates :login, :email, :presence => true
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# Conditional
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validates :description, :presence => true, :if => :published?
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validates :description, :presence => true, :if => lambda { |obj| .. }
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# On
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validates :title, :presence => true, :on => :save # :save | :create | :update
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end
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### Custom validations
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class Person < ActiveRecord::Base
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validate :foo_cant_be_nil
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def foo_cant_be_nil
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errors.add(:foo, 'cant be nil') if foo.nil?
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end
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end
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### Errors
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record.errors.valid? #=> false
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record.errors #=> { :name => ["can't be blank"] }
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record.errors.messages #=> { :name => ["can't be blank"] }
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record.errors[:name].any?
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API
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---
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items = Model.find_by_email(email)
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items = Model.where(first_name: "Harvey")
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item = Model.find(id)
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item.serialize_hash
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item.new_record?
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item.create # Same an #new then #save
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item.create! # Same as above, but raises an Exception
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item.save
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item.save! # Same as above, but raises an Exception
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item.update
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item.update_attributes
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item.update_attributes!
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item.valid?
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item.invalid?
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* [Guides: callbacks](http://guides.rubyonrails.org/active_record_validations_callbacks.html)
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### Sorting
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posts.order(:title)
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posts.order(:title).reverse
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### Mass updates
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# Updates person id 15
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Person.update 15, name: "John", age: 24
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Person.update [1,2], [{name: "John"}, {name: "foo"}]
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### Joining
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Student.joins(:schools).where(:schools => { :type => 'public' })
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Student.joins(:schools).where('schools.type' => 'public' )
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### Serialize
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class User < ActiveRecord::Base
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serialize :preferences
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end
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user = User.create(:preferences => { "background" => "black", "display" => large })
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You can also specify a class option as the second parameter that’ll raise an
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exception if a serialized object is retrieved as a descendant of a class not in
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the hierarchy.
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class User < ActiveRecord::Base
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serialize :preferences, Hash
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end
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user = User.create(:preferences => %w( one two three ))
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User.find(user.id).preferences # raises SerializationTypeMismatch
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Overriding accessors
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--------------------
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class Song < ActiveRecord::Base
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# Uses an integer of seconds to hold the length of the song
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def length=(minutes)
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write_attribute(:length, minutes.to_i * 60)
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end
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def length
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read_attribute(:length) / 60
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end
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end
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* http://api.rubyonrails.org/classes/ActiveRecord/Base.html
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Callbacks
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---------
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after_create
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after_initialize
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after_validation
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after_save
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after_commit
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