# frozen_string_literal: true
require "concurrent/map"
module ActiveModel
# Raised when an attribute is not defined.
#
# class User < ActiveRecord::Base
# has_many :pets
# end
#
# user = User.first
# user.pets.select(:id).first.user_id
# # => ActiveModel::MissingAttributeError: missing attribute 'user_id' for Pet
class MissingAttributeError < NoMethodError
end
# = 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:
#
# * <tt>include ActiveModel::AttributeMethods</tt> in your class.
# * Call each of its methods you want to add, such as +attribute_method_suffix+
# or +attribute_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
module AttributeMethods
extend ActiveSupport::Concern
NAME_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?=]?\z/
CALL_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?]?\z/
included do
class_attribute :attribute_aliases, instance_writer: false, default: {}
class_attribute :attribute_method_patterns, instance_writer: false, default: [ ClassMethods::AttributeMethodPattern.new ]
end
module ClassMethods
# Declares a method available for all attributes with the given prefix.
# Uses +method_missing+ and <tt>respond_to?</tt> to rewrite the method.
#
# #{prefix}#{attr}(*args, &block)
#
# to
#
# #{prefix}attribute(#{attr}, *args, &block)
#
# An instance method <tt>#{prefix}attribute</tt> 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
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 <tt>respond_to?</tt> to rewrite the method.
#
# #{attr}#{suffix}(*args, &block)
#
# to
#
# attribute#{suffix}(#{attr}, *args, &block)
#
# An <tt>attribute#{suffix}</tt> 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
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 a method available for all attributes with the given prefix
# and suffix. Uses +method_missing+ and <tt>respond_to?</tt> to rewrite
# the method.
#
# #{prefix}#{attr}#{suffix}(*args, &block)
#
# to
#
# #{prefix}attribute#{suffix}(#{attr}, *args, &block)
#
# An <tt>#{prefix}attribute#{suffix}</tt> 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'
def attribute_method_affix(*affixes)
self.attribute_method_patterns += affixes.map! { |affix| AttributeMethodPattern.new(**affix) }
undefine_attribute_methods
end
# 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
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
def eagerly_generate_alias_attribute_methods(new_name, old_name) # :nodoc:
ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |code_generator|
generate_alias_attribute_methods(code_generator, new_name, old_name)
end
end
def generate_alias_attribute_methods(code_generator, new_name, old_name) # :nodoc:
ActiveSupport::CodeGenerator.batch(code_generator, __FILE__, __LINE__) do |owner|
attribute_method_patterns.each do |pattern|
alias_attribute_method_definition(code_generator, pattern, new_name, old_name)
end
attribute_method_patterns_cache.clear
end
end
def alias_attribute_method_definition(code_generator, pattern, new_name, old_name) # :nodoc:
method_name = pattern.method_name(new_name).to_s
target_name = pattern.method_name(old_name).to_s
parameters = pattern.parameters
mangled_name = build_mangled_name(target_name)
call_args = []
call_args << parameters if parameters
define_call(code_generator, method_name, target_name, mangled_name, parameters, call_args, namespace: :alias_attribute, as: method_name)
end
# Is +new_name+ an alias?
def attribute_alias?(new_name)
attribute_aliases.key? new_name.to_s
end
# Returns the original name for the alias +name+
def attribute_alias(name)
attribute_aliases[name.to_s]
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
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
# 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
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
def define_attribute_method_pattern(pattern, attr_name, owner:, as:, override: false) # :nodoc:
canonical_method_name = pattern.method_name(attr_name)
public_method_name = pattern.method_name(as)
# If defining a regular attribute method, we don't override methods that are explicitly
# defined in parent classes.
if instance_method_already_implemented?(public_method_name)
# However, for `alias_attribute`, we always define the method.
# We check for override second because `instance_method_already_implemented?`
# also check for dangerous methods.
return unless override
end
generate_method = "define_method_#{pattern.proxy_target}"
if respond_to?(generate_method, true)
send(generate_method, attr_name.to_s, owner: owner, as: as)
else
define_proxy_call(
owner,
canonical_method_name,
pattern.proxy_target,
pattern.parameters,
attr_name.to_s,
namespace: :active_model_proxy,
as: public_method_name
)
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
def undefine_attribute_methods
generated_attribute_methods.module_eval do
undef_method(*instance_methods)
end
attribute_method_patterns_cache.clear
end
def aliases_by_attribute_name # :nodoc:
@aliases_by_attribute_name ||= Hash.new { |h, k| h[k] = [] }
end
private
def inherited(base) # :nodoc:
super
base.class_eval do
@attribute_method_patterns_cache = nil
@aliases_by_attribute_name = nil
@generated_attribute_methods = nil
end
end
def resolve_attribute_name(name)
attribute_aliases.fetch(super, &:itself)
end
def generated_attribute_methods
@generated_attribute_methods ||= Module.new.tap { |mod| include mod }
end
def instance_method_already_implemented?(method_name)
generated_attribute_methods.method_defined?(method_name)
end
# 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).
def attribute_method_patterns_cache
@attribute_method_patterns_cache ||= Concurrent::Map.new(initial_capacity: 4)
end
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
# 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.
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
def build_mangled_name(name)
mangled_name = name
unless NAME_COMPILABLE_REGEXP.match?(name)
mangled_name = :"__temp__#{name.unpack1("h*")}"
end
mangled_name
end
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
class AttributeMethodPattern # :nodoc:
attr_reader :prefix, :suffix, :proxy_target, :parameters
AttributeMethod = Struct.new(:proxy_target, :attr_name)
def initialize(prefix: "", suffix: "", parameters: nil)
@prefix = prefix
@suffix = suffix
@parameters = parameters.nil? ? "..." : parameters
@regex = /\A(?:#{Regexp.escape(@prefix)})(.*)(?:#{Regexp.escape(@suffix)})\z/
@proxy_target = "#{@prefix}attribute#{@suffix}"
@method_name = "#{prefix}%s#{suffix}"
end
def match(method_name)
if @regex =~ method_name
AttributeMethod.new(proxy_target, $1)
end
end
def method_name(attr_name)
@method_name % attr_name
end
end
end
# Allows access to the object attributes, which are held in the hash
# returned by <tt>attributes</tt>, as though they were first-class
# methods. So a +Person+ class with a +name+ attribute can for example use
# <tt>Person#name</tt> and <tt>Person#name=</tt> and never directly use
# the attributes hash -- except for multiple assignments with
# <tt>ActiveRecord::Base#attributes=</tt>.
#
# It's also possible to instantiate related objects, so a <tt>Client</tt>
# class belonging to the +clients+ table with a +master_id+ foreign key
# can instantiate master through <tt>Client#master</tt>.
def method_missing(method, ...)
if respond_to_without_attributes?(method, true)
super
else
match = matched_attribute_method(method.name)
match ? attribute_missing(match, ...) : super
end
end
# +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.
def attribute_missing(match, ...)
__send__(match.proxy_target, match.attr_name, ...)
end
# A +Person+ instance with a +name+ attribute can ask
# <tt>person.respond_to?(:name)</tt>, <tt>person.respond_to?(:name=)</tt>,
# and <tt>person.respond_to?(:name?)</tt> which will all return +true+.
alias :respond_to_without_attributes? :respond_to?
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
private
def attribute_method?(attr_name)
respond_to_without_attributes?(:attributes) && attributes.include?(attr_name)
end
# Returns a struct representing the matching attribute method.
# The struct's attributes are prefix, base and suffix.
def matched_attribute_method(method_name)
matches = self.class.send(:attribute_method_patterns_matching, method_name)
matches.detect { |match| attribute_method?(match.attr_name) }
end
def missing_attribute(attr_name, stack)
raise ActiveModel::MissingAttributeError, "missing attribute '#{attr_name}' for #{self.class}", stack
end
def _read_attribute(attr)
__send__(attr)
end
module AttrNames # :nodoc:
DEF_SAFE_NAME = /\A[a-zA-Z_]\w*\z/
# We want to generate the methods via module_eval rather than
# define_method, because define_method is slower on dispatch.
#
# But sometimes the database might return columns with
# characters that are not allowed in normal method names (like
# 'my_column(omg)'. So to work around this we first define with
# the __temp__ identifier, and then use alias method to rename
# it to what we want.
#
# We are also defining a constant to hold the frozen string of
# the attribute name. Using a constant means that we do not have
# to allocate an object on each call to the attribute method.
# Making it frozen means that it doesn't get duped when used to
# key the @attributes in read_attribute.
def self.define_attribute_accessor_method(owner, attr_name, writer: false)
method_name = "#{attr_name}#{'=' if writer}"
if attr_name.ascii_only? && DEF_SAFE_NAME.match?(attr_name)
yield method_name, "'#{attr_name}'"
else
safe_name = attr_name.unpack1("h*")
const_name = "ATTR_#{safe_name}"
const_set(const_name, attr_name) unless const_defined?(const_name)
temp_method_name = "__temp__#{safe_name}#{'=' if writer}"
attr_name_expr = "::ActiveModel::AttributeMethods::AttrNames::#{const_name}"
yield temp_method_name, attr_name_expr
end
end
end
end
end