oneuptim · February 16, 2017 02:56 · May 28, 2014 · Jan 6, 2012
diff --git a/index.md b/index.md
@@ -74,7 +74,7 @@ Or HABTM:
 
 And in migrations:
 
-    create_table :images do
+    create_table :images do |t|
       t.references :post, :polymorphic => true
     end
 

diff --git a/index.md b/index.md
@@ -0,0 +1,298 @@
+# 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.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?
+
+
+http://guides.rubyonrails.org/active_record_validations_callbacks.html
+
+### 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
+    end
+
+ * http://api.rubyonrails.org/classes/ActiveRecord/Base.html
+
+Callbacks
+---------
+
+    after_create
+    after_initialize
+    after_validation
+    after_save
+    after_commit