$ rails g model User
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
belongs_to :parent, :foreign_key => 'parent_id' class_name: 'Folder'
has_many :folders, :foreign_key => 'parent_id', class_name: 'Folder'
has_many :comments, :order => "posted_on"
has_many :comments, :include => :author
has_many :people, :class_name => "Person"
has_many :people, :conditions => "deleted = 0"
has_many :tracks, :order => "position"
has_many :comments, :dependent => :nullify
has_many :comments, :dependent => :destroy
has_many :tags, :as => :taggable
has_many :reports, :readonly => true
has_many :subscribers, :through => :subscriptions, class_name: "User", :source => :user
has_many :subscribers, :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'
belongs_to :author,
:dependent => :destroy # or :delete
:class_name => "Person"
:select => "*"
:counter_cache => true
:counter_cache => :custom_counter
:include => "Book"
:readonly => true
:conditions => 'published = true'
:touch => true
:touch => :authors_last_updated_at
:primary_key => "name"
:foreign_key => "author_name"
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}"
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
# Returns one record
Person.find_by_name(name)
Person.find_last_by_name(name)
Person.find_or_create_by_name(name)
Person.find_or_initialize_by_name(name)
# Returns a list of recordns
Person.find_all_by_name(name)
# Add a bang to make it raise an exception
Person.find_by_name!(name)
# You may use `scoped` instead of `find`
Person.scoped_by_user_name
$ rake db:migrate
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)
create_table
change_table
drop_table
add_column
change_column
rename_column
remove_column
add_index
remove_index
t.references :category # kinda same as t.integer :category_id
# Can have different types
t.references :category, polymorphic: true
$ 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
class Person < ActiveRecord::Base
validates :name, presence: true
validates :terms, acceptance: true
validates :email, confirmation: true
validates :slug, uniqueness: true
validates :slug, uniqueness: { case_sensitive: false }
validates :holiday, uniqueness: { scope: :year, :message => "only once a year" }
validates :code, format: /regex/
validates :code, format: { with: /regex/ }
validates :name, length: { minimum: 2 }
validates :bio, length: { maximum: 500 }
validates :password, length: { in: => 6..20 }
validates :number, length: { is: => 6 }
validates :gender, inclusion: %w(male female)
validates :gender, inclusion: { in: %w(male female) }
validates :lol, exclusion: %w(xyz)
validates :points, numericality: true
validates :played, numericality: { only_integer: true }
# ... greater_than, greater_than_or_equal_to,
# ... less_than, less_than_or_equal_to
# ... odd, even, equal_to
# Validate the associated records to ensure they're valid as well
has_many :books
validates_associated :books
# Length (full enchalada)
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" }
# Multiple
validates :login, :email, presence: true
# Conditional
validates :description, presence: true, if: :published?
validates :description, presence: true, if: lambda { |obj| .. }
validates :title, presence: true, on: :save # :save | :create | :update
end
class Person < ActiveRecord::Base
validates :terms_of_service, :acceptance => true
end
class Library < ActiveRecord::Base
has_many :books
validates_associated :books
end
class Person < ActiveRecord::Base
validates :email, :confirmation => true
end
class Product < ActiveRecord::Base
validates :legacy_code, :format => { :with => /\A[a-zA-Z]+\z/,
:message => "Only letters allowed" }
end
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
class Player < ActiveRecord::Base
validates :points, :numericality => true
validates :games_played, :numericality => { :only_integer => true }
end
class Person < ActiveRecord::Base
validates :name, :login, :email, :presence => true
end
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
record.errors.valid? #=> false
record.errors #=> { :name => ["can't be blank"] }
record.errors.messages #=> { :name => ["can't be blank"] }
record.errors[:name].any?
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?
# Updates person id 15
Person.update 15, name: "John", age: 24
Person.update [1,2], [{name: "John"}, {name: "foo"}]
Student.joins(:schools).where(:schools => { :type => 'public' })
Student.joins(:schools).where('schools.type' => 'public' )
where("name = ?", "John")
where(["name = :name", { name: "John" }])
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
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
end
after_create
after_initialize
after_validation
after_save
after_commit
items = Model
.where(first_name: 'Harvey')
.where('id = 3')
.where('id = ?', 3)
.order(:title)
.order(title: :desc)
.order("title DESC")
.reorder(:title) # discards other .order's
.rewhere(...) # discards other .where's
.limit(2)
.offset(1)
.uniq
Advanced:
.select(:id)
.select([:id, :name])
.group(:name) # GROUP BY name
.group('name AS grouped_name, age')
.having('SUM(price) > 30') # needs to be chained with .group
.includes(:user)
.includes(user: [:articles])
.references(:posts)
# .where("posts.name = 'foo'").references(:posts)
item = Model.find(id)
item = Model.find_by_email(email)
item = Model.where(email: email).first
Model
.exists?(5)
.exists?(name: "David")
.first
.last
.find_nth(4, [offset])
item.new_record?
item.persisted?
item.destroyed?
item.serialize_hash
item.save
item.save! # Same as above, but raises an Exception
item.update name: 'John' # Saves immediately
item.update! name: 'John'
item.update_column :name, 'John' # skips validations and callbacks
item.update_columns name: 'John'
item.update_columns! name: 'John'
item.touch # updates :updated_at
item.touch :published_at
item.destroy
item.delete # skips callbacks
Model.create # Same an #new then #save
Model.create! # Same as above, but raises an Exception
item.attributes # #<Hash>
item.attributes = { name: 'John' } # Merges attributes in. Doesn't save.
item.assign_attributes name: 'John' # Same as above
item.changed?
item.changed # ['name']
item.changed_attributes # { 'name' => 'Bob' } - original values
item.changes # { 'name' => ['Bob', 'Robert'] }
item.previous_changes # available after #save
item.restore_attributes
item.name = 'Robert'
item.name_was # 'Bob'
item.name_change # [ 'Bob', 'Robert' ]
item.name_changed? # true
item.name_changed?(from: 'Bob', to: 'Robert')
item.valid?
item.invalid?
Person.count
Person.count(:age) # counts non-nil's
Person.average(:age)
Person.maximum(:age)
Person.minimum(:age)
Person.sum('2 * age')
Person.calculate(:count, :all)
Advanced:
Person.distinct.count
Person.group(:city).count