Changing READMEs to refer to ApplicationRecord.

Author: wangjohn

README.md

@@ -11,7 +11,8 @@ application into three layers, each with a specific responsibility.
 The _Model layer_ represents your domain model (such as Account, Product,
 Person, Post, etc.) and encapsulates the business logic that is specific to
 your application. In Rails, database-backed model classes are derived from
-`ActiveRecord::Base`. Active Record allows you to present the data from
+`ActiveRecord::Base` through an application specific subclass called
+`ApplicationRecord`. Active Record allows you to present the data from
 database rows as objects and embellish these data objects with business logic
 methods. You can read more about Active Record in its [README](activerecord/README.rdoc).
 Although most Rails models are backed by a database, models can also be ordinary
@@ -23,7 +24,8 @@ providing a suitable response. Usually this means returning HTML, but Rails cont
 can also generate XML, JSON, PDFs, mobile-specific views, and more. Controllers load and
 manipulate models, and render view templates in order to generate the appropriate HTTP response.
 In Rails, incoming requests are routed by Action Dispatch to an appropriate controller, and
-controller classes are derived from `ActionController::Base`. Action Dispatch and Action Controller
+controller classes are derived from `ActionController::Base` through an application specific 
+subclass called `ApplicationController`. Action Dispatch and Action Controller
 are bundled together in Action Pack. You can read more about Action Pack in its
 [README](actionpack/README.rdoc).
 

activerecord/README.rdoc

@@ -2,10 +2,11 @@
 
 Active Record connects classes to relational database tables to establish an
 almost zero-configuration persistence layer for applications. The library
-provides a base class that, when subclassed, sets up a mapping between the new
-class and an existing table in the database. In the context of an application,
-these classes are commonly referred to as *models*. Models can also be
-connected to other models; this is done by defining *associations*.
+provides a base class, and subclassing an application specific version of
+this base class sets up a mapping between the new class and an existing
+table in the database. In the context of an application, these classes are
+commonly referred to as *models*. Models can also be connected to other
+models; this is done by defining *associations*.
 
 Active Record relies heavily on naming in that it uses class and association
 names to establish mappings between respective database tables and foreign key
@@ -17,7 +18,7 @@ A short rundown of some of the major features:
 
 * Automated mapping between classes and tables, attributes and columns.
 
-   class Product < ActiveRecord::Base
+   class Product < ApplicationRecord
    end
 
   {Learn more}[link:classes/ActiveRecord/Base.html]
@@ -37,7 +38,7 @@ This would also define the following accessors: `Product#name` and
 
 * Associations between objects defined by simple class methods.
 
-   class Firm < ActiveRecord::Base
+   class Firm < ApplicationRecord
      has_many   :clients
      has_one    :account
      belongs_to :conglomerate
@@ -48,7 +49,7 @@ This would also define the following accessors: `Product#name` and
 
 * Aggregations of value objects.
 
-   class Account < ActiveRecord::Base
+   class Account < ApplicationRecord
      composed_of :balance, class_name: 'Money',
                  mapping: %w(balance amount)
      composed_of :address,
@@ -60,7 +61,7 @@ This would also define the following accessors: `Product#name` and
 
 * Validation rules that can differ for new or existing objects.
 
-    class Account < ActiveRecord::Base
+    class Account < ApplicationRecord
       validates :subdomain, :name, :email_address, :password, presence: true
       validates :subdomain, uniqueness: true
       validates :terms_of_service, acceptance: true, on: :create
@@ -72,7 +73,7 @@ This would also define the following accessors: `Product#name` and
 
 * Callbacks available for the entire life cycle (instantiation, saving, destroying, validating, etc.).
 
-   class Person < ActiveRecord::Base
+   class Person < ApplicationRecord
      before_destroy :invalidate_payment_plan
      # the `invalidate_payment_plan` method gets called just before Person#destroy
    end
@@ -82,7 +83,7 @@ This would also define the following accessors: `Product#name` and
 
 * Inheritance hierarchies.
 
-   class Company < ActiveRecord::Base; end
+   class Company < ApplicationRecord; end
    class Firm < Company; end
    class Client < Company; end
    class PriorityClient < Client; end