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::AttributeMethods
in your class. -
Call each of its methods you want to add, such as
attribute_method_suffix
orattribute_method_prefix
. -
Call
define_attribute_methods
after the other methods are called. -
Define the various generic
_attribute
methods that you have declared. -
Define an
attributes
method 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 | = | /\A[a-zA-Z_]\w*[!?]?\z/ |
NAME_COMPILABLE_REGEXP | = | /\A[a-zA-Z_]\w*[!?=]?\z/ |
Instance Public methods
attribute_missing(match, *args, &block) Link
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.
method_missing(method, *args, &block) Link
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 assignments 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 activemodel/lib/active_model/attribute_methods.rb, line 464 def method_missing(method, *args, &block) if respond_to_without_attributes?(method, true) super else match = matched_attribute_method(method.to_s) match ? attribute_missing(match, *args, &block) : super end end
respond_to?(method, include_private_methods = false) Link
# File activemodel/lib/active_model/attribute_methods.rb, line 486 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 !matched_attribute_method(method.to_s).nil? end end
respond_to_without_attributes?(method, include_private_methods = false) Link
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
.