$ 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'
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.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
class Person < ActiveRecord::Base
# Non empty
validates :name, :presence => true
# Checkboxes
validates :terms_of_service, :acceptance => true
# Validate the associated records to ensure they're valid as well
has_many :books
validates_associated :books
# Confirmation (like passwords)
validates :email, :confirmation => true
# Unique
validates :slug, :uniqueness => true
validates :slug, :uniqueness => { :case_sensitive => false }
validates :holiday, :uniqueness => { :scope => :year, :message => "only once a year" }
# Format
validates :legacy_code, :format => {
:with => /\A[a-zA-Z]+\z/,
:message => "Only letters allowed"
}
# Length
validates :name, :length => { :minimum => 2 }
validates :bio, :length => { :maximum => 500 }
validates :password, :length => { :in => 6..20 }
validates :number, :length => { :is => 6 }
# 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"
}
end
# Numeric
validates :points, :numericality => true
validates :games_played, :numericality => { :only_integer => true }
# Multiple
validates :login, :email, :presence => true
# Conditional
validates :description, :presence => true, :if => :published?
validates :description, :presence => true, :if => lambda { |obj| .. }
# On
validates :title, :presence => true, :on => :save # :save | :create | :update
# Custom hook
validate :check_for_bugs
def check_for_bugs
errors.add :bugs, "are so many" if bugs.any?
end
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
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?
http://guides.rubyonrails.org/active_record_validations_callbacks.html
# 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' )
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