module ActiveModel::AttributeMethods::ClassMethods
Public Instance Methods
Allows you to make aliases for attributes.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_suffix '_short?' define_attribute_methods :name alias_attribute :nickname, :name private def attribute_short?(attr) send(attr).length < 5 end end person = Person.new person.name = 'Bob' person.name # => "Bob" person.nickname # => "Bob" person.name_short? # => true person.nickname_short? # => true
# File lib/active_model/attribute_methods.rb, line 203 def alias_attribute(new_name, old_name) old_name = old_name.to_s new_name = new_name.to_s self.attribute_aliases = attribute_aliases.merge(new_name => old_name) aliases_by_attribute_name[old_name] << new_name eagerly_generate_alias_attribute_methods(new_name, old_name) end
Returns the original name for the alias name
# File lib/active_model/attribute_methods.rb, line 245 def attribute_alias(name) attribute_aliases[name.to_s] end
Is new_name
an alias?
# File lib/active_model/attribute_methods.rb, line 240 def attribute_alias?(new_name) attribute_aliases.key? new_name.to_s end
Declares a method available for all attributes with the given prefix and suffix. Uses method_missing
and respond_to?
to rewrite the method.
#{prefix}#{attr}#{suffix}(*args, &block)
to
#{prefix}attribute#{suffix}(#{attr}, *args, &block)
An #{prefix}attribute#{suffix}
instance method must exist and accept at least the attr
argument.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_affix prefix: 'reset_', suffix: '_to_default!' define_attribute_methods :name private def reset_attribute_to_default!(attr) send("#{attr}=", 'Default Name') end end person = Person.new person.name # => 'Gem' person.reset_name_to_default! person.name # => 'Default Name'
# File lib/active_model/attribute_methods.rb, line 175 def attribute_method_affix(*affixes) self.attribute_method_patterns += affixes.map! { |affix| AttributeMethodPattern.new(**affix) } undefine_attribute_methods end
Declares a method available for all attributes with the given prefix. Uses method_missing
and respond_to?
to rewrite the method.
#{prefix}#{attr}(*args, &block)
to
#{prefix}attribute(#{attr}, *args, &block)
An instance method #{prefix}attribute
must exist and accept at least the attr
argument.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_prefix 'clear_' define_attribute_methods :name private def clear_attribute(attr) send("#{attr}=", nil) end end person = Person.new person.name = 'Bob' person.name # => "Bob" person.clear_name person.name # => nil
# File lib/active_model/attribute_methods.rb, line 106 def attribute_method_prefix(*prefixes, parameters: nil) self.attribute_method_patterns += prefixes.map! { |prefix| AttributeMethodPattern.new(prefix: prefix, parameters: parameters) } undefine_attribute_methods end
Declares a method available for all attributes with the given suffix. Uses method_missing
and respond_to?
to rewrite the method.
#{attr}#{suffix}(*args, &block)
to
attribute#{suffix}(#{attr}, *args, &block)
An attribute#{suffix}
instance method must exist and accept at least the attr
argument.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_suffix '_short?' define_attribute_methods :name private def attribute_short?(attr) send(attr).length < 5 end end person = Person.new person.name = 'Bob' person.name # => "Bob" person.name_short? # => true
# File lib/active_model/attribute_methods.rb, line 140 def attribute_method_suffix(*suffixes, parameters: nil) self.attribute_method_patterns += suffixes.map! { |suffix| AttributeMethodPattern.new(suffix: suffix, parameters: parameters) } undefine_attribute_methods end
Declares an attribute that should be prefixed and suffixed by ActiveModel::AttributeMethods
.
To use, pass an attribute name (as string or symbol). Be sure to declare define_attribute_method
after you define any prefix, suffix or affix method, or they will not hook in.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_suffix '_short?' # Call to define_attribute_method must appear after the # attribute_method_prefix, attribute_method_suffix or # attribute_method_affix declarations. define_attribute_method :name private def attribute_short?(attr) send(attr).length < 5 end end person = Person.new person.name = 'Bob' person.name # => "Bob" person.name_short? # => true
# File lib/active_model/attribute_methods.rb, line 311 def define_attribute_method(attr_name, _owner: generated_attribute_methods, as: attr_name) ActiveSupport::CodeGenerator.batch(_owner, __FILE__, __LINE__) do |owner| attribute_method_patterns.each do |pattern| define_attribute_method_pattern(pattern, attr_name, owner: owner, as: as) end attribute_method_patterns_cache.clear end end
Declares the attributes that should be prefixed and suffixed by ActiveModel::AttributeMethods
.
To use, pass attribute names (as strings or symbols). Be sure to declare define_attribute_methods
after you define any prefix, suffix, or affix methods, or they will not hook in.
class Person include ActiveModel::AttributeMethods attr_accessor :name, :age, :address attribute_method_prefix 'clear_' # Call to define_attribute_methods must appear after the # attribute_method_prefix, attribute_method_suffix or # attribute_method_affix declarations. define_attribute_methods :name, :age, :address private def clear_attribute(attr) send("#{attr}=", nil) end end
# File lib/active_model/attribute_methods.rb, line 272 def define_attribute_methods(*attr_names) ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |owner| attr_names.flatten.each do |attr_name| define_attribute_method(attr_name, _owner: owner) aliases_by_attribute_name[attr_name.to_s].each do |aliased_name| generate_alias_attribute_methods owner, aliased_name, attr_name end end end end
Removes all the previously dynamically defined methods from the class, including alias attribute methods.
class Person include ActiveModel::AttributeMethods attr_accessor :name attribute_method_suffix '_short?' define_attribute_method :name alias_attribute :first_name, :name private def attribute_short?(attr) send(attr).length < 5 end end person = Person.new person.name = 'Bob' person.first_name # => "Bob" person.name_short? # => true Person.undefine_attribute_methods person.name_short? # => NoMethodError person.first_name # => NoMethodError
# File lib/active_model/attribute_methods.rb, line 375 def undefine_attribute_methods generated_attribute_methods.module_eval do undef_method(*instance_methods) end attribute_method_patterns_cache.clear end
Private Instance Methods
The methods method_missing
and respond_to?
of this module are invoked often in a typical rails, both of which invoke the method matched_attribute_method
. The latter method iterates through an array doing regular expression matches, which results in a lot of object creations. Most of the time it returns a nil
match. As the match result is always the same given a method_name
, this cache is used to alleviate the GC, which ultimately also speeds up the app significantly (in our case our test suite finishes 10% faster with this cache).
# File lib/active_model/attribute_methods.rb, line 417 def attribute_method_patterns_cache @attribute_method_patterns_cache ||= Concurrent::Map.new(initial_capacity: 4) end
# File lib/active_model/attribute_methods.rb, line 421 def attribute_method_patterns_matching(method_name) attribute_method_patterns_cache.compute_if_absent(method_name) do attribute_method_patterns.filter_map { |pattern| pattern.match(method_name) } end end
# File lib/active_model/attribute_methods.rb, line 445 def build_mangled_name(name) mangled_name = name unless NAME_COMPILABLE_REGEXP.match?(name) mangled_name = :"__temp__#{name.unpack1("h*")}" end mangled_name end
# File lib/active_model/attribute_methods.rb, line 455 def define_call(code_generator, name, target_name, mangled_name, parameters, call_args, namespace:, as:) code_generator.define_cached_method(mangled_name, as: as, namespace: namespace) do |batch| body = if CALL_COMPILABLE_REGEXP.match?(target_name) "self.#{target_name}(#{call_args.join(", ")})" else call_args.unshift(":'#{target_name}'") "send(#{call_args.join(", ")})" end batch << "def #{mangled_name}(#{parameters || ''})" << body << "end" end end
Define a method ‘name` in `mod` that dispatches to `send` using the given `extra` args. This falls back on `send` if the called name cannot be compiled.
# File lib/active_model/attribute_methods.rb, line 430 def define_proxy_call(code_generator, name, proxy_target, parameters, *call_args, namespace:, as: name) mangled_name = build_mangled_name(name) call_args.map!(&:inspect) call_args << parameters if parameters # We have to use a different namespace for every target method, because # if someone defines an attribute that look like an attribute method we could clash, e.g. # attribute :title_was # attribute :title namespace = :"#{namespace}_#{proxy_target}" define_call(code_generator, name, proxy_target, mangled_name, parameters, call_args, namespace: namespace, as: as) end
# File lib/active_model/attribute_methods.rb, line 400 def generated_attribute_methods @generated_attribute_methods ||= Module.new.tap { |mod| include mod } end
# File lib/active_model/attribute_methods.rb, line 404 def instance_method_already_implemented?(method_name) generated_attribute_methods.method_defined?(method_name) end
# File lib/active_model/attribute_methods.rb, line 396 def resolve_attribute_name(name) attribute_aliases.fetch(super, &:itself) end