Rails Models
Generating models
$ rails g model User
Associations
belongs_to
has_one
has_many
has_many :through
has_one :through
has_and_belongs_to_many
belongs_to :author,
class_name: 'User',
dependent: :destroy // delete this
Has many
has_many :comments, :order => "posted_on"
has_many :comments, :include => :author
has_many :people, :class_name => "Person", :conditions => "deleted = 0", :order => "name"
has_many :tracks, :order => "position", :dependent => :destroy
has_many :comments, :dependent => :nullify
has_many :tags, :as => :taggable
has_many :reports, :readonly => true
has_many :subscribers, :through => :subscriptions, :source => :user
has_many :subscribers, :class_name => "Person", :finder_sql =>
'SELECT DISTINCT people.* ' +
'FROM people p, post_subscriptions ps ' +
'WHERE ps.post_id = #{id} AND ps.person_id = p.id ' +
'ORDER BY p.first_name'
Many-to-many
If you have a join model:
class Programmer < ActiveRecord::Base
has_many :assignments
has_many :projects, :through => :assignments
end
class Project < ActiveRecord::Base
has_many :assignments
has_many :programmers, :through => :assignments
end
class Assignment
belongs_to :project
belongs_to :programmer
end
Or HABTM:
has_and_belongs_to_many :projects
has_and_belongs_to_many :projects, :include => [ :milestones, :manager ]
has_and_belongs_to_many :nations, :class_name => "Country"
has_and_belongs_to_many :categories, :join_table => "prods_cats"
has_and_belongs_to_many :categories, :readonly => true
has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :delete_sql =>
"DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}"
Polymorphic associations
class Post
has_many :attachments, :as => :parent
end
class Image
belongs_to :parent, :polymorphic => true
end
And in migrations:
create_table :images do |t|
t.references :post, :polymorphic => true
end
Migrations
Run migrations
$ rake db:migrate
Migrations
create_table :users do |t|
t.string :name
t.text :description
t.primary_key :id
t.string
t.text
t.integer
t.float
t.decimal
t.datetime
t.timestamp
t.time
t.date
t.binary
t.boolean
end
options:
:null (boolean)
:limit (integer)
:default
:precision (integer)
:scale (integer)
Tasks
create_table
change_table
drop_table
add_column
change_column
rename_column
remove_column
add_index
remove_index
Associations
t.references :category # kinda same as t.integer :category_id
# Can have different types
t.references :category, polymorphic: true
Add/remove columns
$ rails generate migration RemovePartNumberFromProducts part_number:string
class RemovePartNumberFromProducts < ActiveRecord::Migration
def up
remove_column :products, :part_number
end
def down
add_column :products, :part_number, :string
end
end
Validation
Validate checkboxes
class Person < ActiveRecord::Base
validates :terms_of_service, :acceptance => true
end
Validate associated records
class Library < ActiveRecord::Base
has_many :books
validates_associated :books
end
Confirmations (like passwords)
class Person < ActiveRecord::Base
validates :email, :confirmation => true
end
Validate format
class Product < ActiveRecord::Base
validates :legacy_code, :format => { :with => /\A[a-zA-Z]+\z/,
:message => "Only letters allowed" }
end
Validate length
class Person < ActiveRecord::Base
validates :name, :length => { :minimum => 2 }
validates :bio, :length => { :maximum => 500 }
validates :password, :length => { :in => 6..20 }
validates :registration_number, :length => { :is => 6 }
validates :content, :length => {
:minimum => 300,
:maximum => 400,
:tokenizer => lambda { |str| str.scan(/\w+/) },
:too_short => "must have at least %{count} words",
:too_long => "must have at most %{count} words"
}
end
Numeric
class Player < ActiveRecord::Base
validates :points, :numericality => true
validates :games_played, :numericality => { :only_integer => true }
end
Non-empty
class Person < ActiveRecord::Base
validates :name, :login, :email, :presence => true
end
custom
class Person < ActiveRecord::Base
validate :foo_cant_be_nil
def foo_cant_be_nil
errors.add(:foo, 'cant be nil') if foo.nil?
end
end
API
items = Model.find_by_email(email)
items = Model.where(first_name: "Harvey")
item = Model.find(id)
item.serialize_hash
item.new_record?
item.create # Same an #new then #save
item.create! # Same as above, but raises an Exception
item.save
item.save! # Same as above, but raises an Exception
item.update
item.update_attributes
item.update_attributes!
item.valid?
item.invalid?Mass updates
# Updates person id 15
Person.update 15, name: "John", age: 24
Person.update [1,2], [{name: "John"}, {name: "foo"}]
Joining
Student.joins(:schools).where(:schools => { :type => 'public' })
Student.joins(:schools).where('schools.type' => 'public' )
Serialize
class User < ActiveRecord::Base
serialize :preferences
end
user = User.create(:preferences => { "background" => "black", "display" => large })
You can also specify a class option as the second parameter that’ll raise an exception if a serialized object is retrieved as a descendant of a class not in the hierarchy.
class User < ActiveRecord::Base
serialize :preferences, Hash
end
user = User.create(:preferences => %w( one two three ))
User.find(user.id).preferences # raises SerializationTypeMismatch
Overriding accessors
class Song < ActiveRecord::Base
# Uses an integer of seconds to hold the length of the song
def length=(minutes)
write_attribute(:length, minutes.to_i * 60)
end
def length
read_attribute(:length) / 60
end
endCallbacks
after_create
after_initialize
after_validation
after_save
after_commit