157 lines
4.3 KiB
Plaintext
157 lines
4.3 KiB
Plaintext
= Active Model - defined interfaces for Rails
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Prior to Rails 3.0, if a plugin or gem developer wanted to be able to have
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an object interact with Action Pack helpers, it was required to either
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copy chunks of code from Rails, or monkey patch entire helpers to make them
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handle objects that did not look like Active Record. This generated code
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duplication and fragile applications that broke on upgrades.
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Active Model is a solution for this problem.
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Active Model provides a known set of interfaces that your objects can implement
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to then present a common interface to the Action Pack helpers. You can include
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functionality from the following modules:
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* Adding attribute magic to your objects
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Add prefixes and suffixes to defined attribute methods...
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class Person
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include ActiveModel::AttributeMethods
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attribute_method_prefix 'clear_'
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define_attribute_methods [:name, :age]
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attr_accessor :name, :age
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def clear_attribute(attr)
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send("#{attr}=", nil)
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end
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end
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...gives you clear_name, clear_age.
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{Learn more}[link:classes/ActiveModel/AttributeMethods.html]
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* Adding callbacks to your objects
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class Person
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extend ActiveModel::Callbacks
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define_model_callbacks :create
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def create
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_run_create_callbacks do
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# Your create action methods here
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end
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end
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end
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...gives you before_create, around_create and after_create class methods that
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wrap your create method.
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{Learn more}[link:classes/ActiveModel/CallBacks.html]
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* For classes that already look like an Active Record object
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class Person
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include ActiveModel::Conversion
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end
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...returns the class itself when sent :to_model
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{Learn more}[link:classes/ActiveModel/Conversion.html]
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* Tracking changes in your object
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Provides all the value tracking features implemented by ActiveRecord...
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person = Person.new
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person.name # => nil
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person.changed? # => false
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person.name = 'bob'
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person.changed? # => true
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person.changed # => ['name']
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person.changes # => { 'name' => [nil, 'bob'] }
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person.name = 'robert'
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person.save
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person.previous_changes # => {'name' => ['bob, 'robert']}
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{Learn more}[link:classes/ActiveModel/Dirty.html]
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* Adding +errors+ support to your object
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Provides the error messages to allow your object to interact with Action Pack
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helpers seamlessly...
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class Person
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def initialize
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@errors = ActiveModel::Errors.new(self)
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end
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attr_accessor :name
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attr_reader :errors
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def validate!
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errors.add(:name, "can not be nil") if name == nil
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end
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def ErrorsPerson.human_attribute_name(attr, options = {})
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"Name"
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end
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end
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... gives you...
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person.errors.full_messages
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# => ["Name Can not be nil"]
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person.errors.full_messages
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# => ["Name Can not be nil"]
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{Learn more}[link:classes/ActiveModel/Errors.html]
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* Testing the compliance of your object
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Use ActiveModel::Lint to test the compliance of your object to the
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basic ActiveModel API...
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{Learn more}[link:classes/ActiveModel/Lint/Tests.html]
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* Providing a human face to your object
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ActiveModel::Naming provides your model with the model_name convention
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and a human_name attribute...
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class NamedPerson
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extend ActiveModel::Naming
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end
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...gives you...
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NamedPerson.model_name #=> "NamedPerson"
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NamedPerson.model_name.human #=> "Named person"
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{Learn more}[link:classes/ActiveModel/Naming.html]
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* Adding observer support to your objects
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ActiveModel::Observers allows your object to implement the Observer
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pattern in a Rails App and take advantage of all the standard observer
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functions.
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{Learn more}[link:classes/ActiveModel/Observer.html]
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* Making your object serializable
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ActiveModel::Serialization provides a standard interface for your object
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to provide to_json or to_xml serialization...
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s = SerialPerson.new
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s.serializable_hash # => {"name"=>nil}
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s.to_json # => "{\"name\":null}"
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s.to_xml # => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<serial-person...
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{Learn more}[link:classes/ActiveModel/Serialization.html]
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