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-== Welcome to Rails
+= Active Model -- model interfaces for Rails
-Rails is a web-application framework that includes everything needed to create
-database-backed web applications according to the Model-View-Control pattern.
+Active Model provides a known set of interfaces for usage in model classes.
+They allow for Action Pack helpers to interact with non-ActiveRecord models,
+for example. Active Model also helps building custom ORMs for use outside of
+the Rails framework.
-This pattern splits the view (also called the presentation) into "dumb"
-templates that are primarily responsible for inserting pre-built data in between
-HTML tags. The model contains the "smart" domain objects (such as Account,
-Product, Person, Post) that holds all the business logic and knows how to
-persist themselves to a database. The controller handles the incoming requests
-(such as Save New Account, Update Product, Show Post) by manipulating the model
-and directing data to the view.
+Prior to Rails 3.0, if a plugin or gem developer wanted to have an object
+interact with Action Pack helpers, it was required to either copy chunks of
+code from Rails, or monkey patch entire helpers to make them handle objects
+that did not exactly conform to the Active Record interface. This would result
+in code duplication and fragile applications that broke on upgrades. Active
+Model solves this by defining an explicit API. You can read more about the
+API in ActiveModel::Lint::Tests.
-In Rails, the model is handled by what's called an object-relational mapping
-layer entitled Active Record. This layer 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
-link:files/vendor/rails/activerecord/README.html.
+Active Model provides a default module that implements the basic API required
+to integrate with Action Pack out of the box: <tt>ActiveModel::Model</tt>.
-The controller and view are handled by the Action Pack, which handles both
-layers by its two parts: Action View and Action Controller. These two layers
-are bundled in a single package due to their heavy interdependence. This is
-unlike the relationship between the Active Record and Action Pack that is much
-more separate. Each of these packages can be used independently outside of
-Rails. You can read more about Action Pack in
-link:files/vendor/rails/actionpack/README.html.
+ class Person
+ include ActiveModel::Model
+ attr_accessor :name, :age
+ validates_presence_of :name
+ end
+
+ person = Person.new(:name => 'bob', :age => '18')
+ person.name # => 'bob'
+ person.age # => 18
+ person.valid? # => false
-== Getting Started
+It includes model name introspections, conversions, translations and
+validations, resulting in a class suitable to be used with Action Pack.
+See <tt>ActiveModel::Model</tt> for more examples.
-1. At the command prompt, create a new Rails application:
- <tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)
+Active Model also provides the following functionality to have ORM-like
+behavior out of the box:
-2. Change directory to <tt>myapp</tt> and start the web server:
- <tt>cd myapp; rails server</tt> (run with --help for options)
+* Add attribute magic to objects
-3. Go to http://localhost:3000/ and you'll see:
- "Welcome aboard: You're riding Ruby on Rails!"
+ class Person
+ include ActiveModel::AttributeMethods
-4. Follow the guidelines to start developing your application. You can find
-the following resources handy:
+ attribute_method_prefix 'clear_'
+ define_attribute_methods [:name, :age]
-* The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
-* Ruby on Rails Tutorial Book: http://www.railstutorial.org/
+ attr_accessor :name, :age
+ def clear_attribute(attr)
+ send("#{attr}=", nil)
+ end
+ end
-== Debugging Rails
+ person.clear_name
+ person.clear_age
-Sometimes your application goes wrong. Fortunately there are a lot of tools that
-will help you debug it and get it back on the rails.
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/AttributeMethods.html]
-First area to check is the application log files. Have "tail -f" commands
-running on the server.log and development.log. Rails will automatically display
-debugging and runtime information to these files. Debugging info will also be
-shown in the browser on requests from 127.0.0.1.
+* Callbacks for certain operations
-You can also log your own messages directly into the log file from your code
-using the Ruby logger class from inside your controllers. Example:
+ class Person
+ extend ActiveModel::Callbacks
+ define_model_callbacks :create
- class WeblogController < ActionController::Base
- def destroy
- @weblog = Weblog.find(params[:id])
- @weblog.destroy
- logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
+ def create
+ run_callbacks :create do
+ # Your create action methods here
+ end
+ end
end
- end
-The result will be a message in your log file along the lines of:
+ This generates +before_create+, +around_create+ and +after_create+
+ class methods that wrap your create method.
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/CallBacks.html]
+
+* Tracking value changes
+
+ The ActiveModel::Dirty module allows for tracking attribute changes:
+
+ person = Person.new
+ person.name # => nil
+ person.changed? # => false
+ person.name = 'bob'
+ person.changed? # => true
+ person.changed # => ['name']
+ person.changes # => { 'name' => [nil, 'bob'] }
+ person.name = 'robert'
+ person.save
+ person.previous_changes # => {'name' => ['bob, 'robert']}
- Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1!
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Dirty.html]
-More information on how to use the logger is at http://www.ruby-doc.org/core/
+* Adding +errors+ interface to objects
-Also, Ruby documentation can be found at http://www.ruby-lang.org/. There are
-several books available online as well:
+ Exposing error messages allows objects to interact with Action Pack
+ helpers seamlessly.
-* Programming Ruby: http://www.ruby-doc.org/docs/ProgrammingRuby/ (Pickaxe)
-* Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
+ class Person
-These two books will bring you up to speed on the Ruby language and also on
-programming in general.
+ def initialize
+ @errors = ActiveModel::Errors.new(self)
+ end
+ attr_accessor :name
+ attr_reader :errors
-== Debugger
+ def validate!
+ errors.add(:name, "can not be nil") if name.nil?
+ end
-Debugger support is available through the debugger command when you start your
-Mongrel or WEBrick server with --debugger. This means that you can break out of
-execution at any point in the code, investigate and change the model, and then,
-resume execution! You need to install ruby-debug to run the server in debugging
-mode. With gems, use <tt>sudo gem install ruby-debug</tt>. Example:
+ def self.human_attribute_name(attr, options = {})
+ "Name"
+ end
+ end
+
+ person.errors.full_messages
+ # => ["Name can not be nil"]
+
+ person.errors.full_messages
+ # => ["Name can not be nil"]
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Errors.html]
- class WeblogController < ActionController::Base
- def index
- @posts = Post.all
- debugger
+* Model name introspection
+
+ class NamedPerson
+ extend ActiveModel::Naming
end
- end
-
-So the controller will accept the action, run the first line, then present you
-with a IRB prompt in the server window. Here you can do things like:
-
- >> @posts.inspect
- => "[#<Post:0x14a6be8
- @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>,
- #<Post:0x14a6620
- @attributes={"title"=>"Rails", "body"=>"Only ten..", "id"=>"2"}>]"
- >> @posts.first.title = "hello from a debugger"
- => "hello from a debugger"
-
-...and even better, you can examine how your runtime objects actually work:
-
- >> f = @posts.first
- => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
- >> f.
- Display all 152 possibilities? (y or n)
-
-Finally, when you're ready to resume execution, you can enter "cont".
-
-
-== Console
-
-The console is a Ruby shell, which allows you to interact with your
-application's domain model. Here you'll have all parts of the application
-configured, just like it is when the application is running. You can inspect
-domain models, change values, and save to the database. Starting the script
-without arguments will launch it in the development environment.
-
-To start the console, run <tt>rails console</tt> from the application
-directory.
-
-Options:
-
-* Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications
- made to the database.
-* Passing an environment name as an argument will load the corresponding
- environment. Example: <tt>rails console production</tt>.
-
-To reload your controllers and models after launching the console run
-<tt>reload!</tt>
-
-More information about irb can be found at:
-link:http://www.rubycentral.org/pickaxe/irb.html
-
-
-== dbconsole
-
-You can go to the command line of your database directly through <tt>rails
-dbconsole</tt>. You would be connected to the database with the credentials
-defined in database.yml. Starting the script without arguments will connect you
-to the development database. Passing an argument will connect you to a different
-database, like <tt>rails dbconsole production</tt>. Currently works for MySQL,
-PostgreSQL and SQLite 3.
-
-== Description of Contents
-
-The default directory structure of a generated Ruby on Rails application:
-
- |-- app
- | |-- assets
- | |-- images
- | |-- javascripts
- | `-- stylesheets
- | |-- controllers
- | |-- helpers
- | |-- mailers
- | |-- models
- | `-- views
- | `-- layouts
- |-- config
- | |-- environments
- | |-- initializers
- | `-- locales
- |-- db
- |-- doc
- |-- lib
- | `-- tasks
- |-- log
- |-- public
- |-- script
- |-- test
- | |-- fixtures
- | |-- functional
- | |-- integration
- | |-- performance
- | `-- unit
- |-- tmp
- | |-- cache
- | |-- pids
- | |-- sessions
- | `-- sockets
- `-- vendor
- |-- assets
- `-- stylesheets
- `-- plugins
-
-app
- Holds all the code that's specific to this particular application.
-
-app/assets
- Contains subdirectories for images, stylesheets, and JavaScript files.
-
-app/controllers
- Holds controllers that should be named like weblogs_controller.rb for
- automated URL mapping. All controllers should descend from
- ApplicationController which itself descends from ActionController::Base.
-
-app/models
- Holds models that should be named like post.rb. Models descend from
- ActiveRecord::Base by default.
-
-app/views
- Holds the template files for the view that should be named like
- weblogs/index.html.erb for the WeblogsController#index action. All views use
- eRuby syntax by default.
-
-app/views/layouts
- Holds the template files for layouts to be used with views. This models the
- common header/footer method of wrapping views. In your views, define a layout
- using the <tt>layout :default</tt> and create a file named default.html.erb.
- Inside default.html.erb, call <% yield %> to render the view using this
- layout.
-
-app/helpers
- Holds view helpers that should be named like weblogs_helper.rb. These are
- generated for you automatically when using generators for controllers.
- Helpers can be used to wrap functionality for your views into methods.
-
-config
- Configuration files for the Rails environment, the routing map, the database,
- and other dependencies.
-
-db
- Contains the database schema in schema.rb. db/migrate contains all the
- sequence of Migrations for your schema.
-
-doc
- This directory is where your application documentation will be stored when
- generated using <tt>rake doc:app</tt>
-
-lib
- Application specific libraries. Basically, any kind of custom code that
- doesn't belong under controllers, models, or helpers. This directory is in
- the load path.
-
-public
- The directory available for the web server. Also contains the dispatchers and the
- default HTML files. This should be set as the DOCUMENT_ROOT of your web
- server.
-
-script
- Helper scripts for automation and generation.
-
-test
- Unit and functional tests along with fixtures. When using the rails generate
- command, template test files will be generated for you and placed in this
- directory.
-
-vendor
- External libraries that the application depends on. Also includes the plugins
- subdirectory. If the app has frozen rails, those gems also go here, under
- vendor/rails/. This directory is in the load path.
+
+ NamedPerson.model_name # => "NamedPerson"
+ NamedPerson.model_name.human # => "Named person"
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Naming.html]
+
+* Observer support
+
+ ActiveModel::Observers allows your object to implement the Observer
+ pattern in a Rails App and take advantage of all the standard observer
+ functions.
+
+ {Learn more}[link:classes/ActiveModel/Observer.html]
+
+* Making objects serializable
+
+ ActiveModel::Serialization provides a standard interface for your object
+ to provide +to_json+ or +to_xml+ serialization.
+
+ s = SerialPerson.new
+ s.serializable_hash # => {"name"=>nil}
+ s.to_json # => "{\"name\":null}"
+ s.to_xml # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Serialization.html]
+
+* Internationalization (i18n) support
+
+ class Person
+ extend ActiveModel::Translation
+ end
+
+ Person.human_attribute_name('my_attribute')
+ # => "My attribute"
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Translation.html]
+
+* Validation support
+
+ class Person
+ include ActiveModel::Validations
+
+ attr_accessor :first_name, :last_name
+
+ validates_each :first_name, :last_name do |record, attr, value|
+ record.errors.add attr, 'starts with z.' if value.to_s[0] == ?z
+ end
+ end
+
+ person = Person.new
+ person.first_name = 'zoolander'
+ person.valid? # => false
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Validations.html]
+
+* Custom validators
+
+ class ValidatorPerson
+ include ActiveModel::Validations
+ validates_with HasNameValidator
+ attr_accessor :name
+ end
+
+ class HasNameValidator < ActiveModel::Validator
+ def validate(record)
+ record.errors[:name] = "must exist" if record.name.blank?
+ end
+ end
+
+ p = ValidatorPerson.new
+ p.valid? # => false
+ p.errors.full_messages # => ["Name must exist"]
+ p.name = "Bob"
+ p.valid? # => true
+
+ {Learn more}[http://api.rubyonrails.org/classes/ActiveModel/Validator.html]
+
+
+== Download and installation
+
+The latest version of Active Model can be installed with RubyGems:
+
+ % [sudo] gem install activemodel
+
+Source code can be downloaded as part of the Rails project on GitHub
+
+* https://github.com/rails/rails/tree/master/activemodel
+
+
+== License
+
+Active Model is released under the MIT license:
+
+* http://www.opensource.org/licenses/MIT
+
+
+== Support
+
+API documentation is at
+
+* http://api.rubyonrails.org
+
+Bug reports and feature requests can be filed with the rest for the Ruby on Rails project here:
+
+* https://github.com/rails/rails/issues
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