module ActiveModel::AttributeMethods
Active Model Attribute Methods¶ ↑
Provides a way to add prefixes and suffixes to your methods as well as
handling the creation of ActiveRecord::Base-like class methods
such as table_name.
The requirements to implement ActiveModel::AttributeMethods
are to:
-
include ActiveModel::AttributeMethodsin your class. -
Call each of its method you want to add, such as
attribute_method_suffixorattribute_method_prefix. -
Call
define_attribute_methodsafter the other methods are called. -
Define the various generic
_attributemethods that you have declared. -
Define an
attributesmethod which returns a hash with each attribute name in your model as hash key and the attribute value as hash value. Hash keys must be strings.
A minimal implementation could be:
class Person include ActiveModel::AttributeMethods attribute_method_affix prefix: 'reset_', suffix: '_to_default!' attribute_method_suffix '_contrived?' attribute_method_prefix 'clear_' define_attribute_methods :name attr_accessor :name def attributes { 'name' => @name } end private def attribute_contrived?(attr) true end def clear_attribute(attr) send("#{attr}=", nil) end def reset_attribute_to_default!(attr) send("#{attr}=", 'Default Name') end end
Constants
- CALL_COMPILABLE_REGEXP
- NAME_COMPILABLE_REGEXP
Public Instance Methods
attribute_missing is like method_missing, but for
attributes. When method_missing is called we check to see if
there is a matching attribute method. If so, we tell
attribute_missing to dispatch the attribute. This method can
be overloaded to customize the behavior.
# File lib/active_model/attribute_methods.rb, line 441 def attribute_missing(match, *args, &block) __send__(match.target, match.attr_name, *args, &block) end
Allows access to the object attributes, which are held in the hash returned
by attributes, as though they were first-class methods. So a
Person class with a name attribute can for
example use Person#name and Person#name= and
never directly use the attributes hash – except for multiple assigns with
ActiveRecord::Base#attributes=.
It's also possible to instantiate related objects, so a
Client class belonging to the clients table with
a master_id foreign key can instantiate master through
Client#master.
# File lib/active_model/attribute_methods.rb, line 428 def method_missing(method, *args, &block) if respond_to_without_attributes?(method, true) super else match = match_attribute_method?(method.to_s) match ? attribute_missing(match, *args, &block) : super end end
# File lib/active_model/attribute_methods.rb, line 449 def respond_to?(method, include_private_methods = false) if super true elsif !include_private_methods && super(method, true) # If we're here then we haven't found among non-private methods # but found among all methods. Which means that the given method is private. false else !match_attribute_method?(method.to_s).nil? end end
A Person instance with a name attribute can ask
person.respond_to?(:name),
person.respond_to?(:name=), and
person.respond_to?(:name?) which will all return
true.
Private Instance Methods
Returns a struct representing the matching attribute method. The struct's attributes are prefix, base and suffix.
# File lib/active_model/attribute_methods.rb, line 469 def match_attribute_method?(method_name) matches = self.class.send(:attribute_method_matchers_matching, method_name) matches.detect { |match| attribute_method?(match.attr_name) } end
# File lib/active_model/attribute_methods.rb, line 474 def missing_attribute(attr_name, stack) raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack end