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require 'thread_safe'
require 'mutex_m'
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
class MissingAttributeError < NoMethodError
end
# == Active \Model Attribute Methods
#
# <tt>ActiveModel::AttributeMethods</tt> provides a way to add prefixes and
# suffixes to your methods as well as handling the creation of
# <tt>ActiveRecord::Base</tt>-like class methods such as +table_name+.
#
# The requirements to implement <tt>ActiveModel::AttributeMethods</tt> are to:
#
# * <tt>include ActiveModel::AttributeMethods</tt> in your class.
# * Call each of its method 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, see below.
#
# 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
#
# Note that whenever you include <tt>ActiveModel::AttributeMethods</tt> in
# your class, it requires you to implement 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.
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, :attribute_method_matchers, instance_writer: false
self.attribute_aliases = {}
self.attribute_method_matchers = [ClassMethods::AttributeMethodMatcher.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)
self.attribute_method_matchers += prefixes.map! { |prefix| AttributeMethodMatcher.new prefix: prefix }
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)
self.attribute_method_matchers += suffixes.map! { |suffix| AttributeMethodMatcher.new suffix: suffix }
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)
# ...
# end
# end
#
# person = Person.new
# person.name # => 'Gem'
# person.reset_name_to_default!
# person.name # => 'Gemma'
def attribute_method_affix(*affixes)
self.attribute_method_matchers += affixes.map! { |affix| AttributeMethodMatcher.new prefix: affix[:prefix], suffix: affix[:suffix] }
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)
self.attribute_aliases = attribute_aliases.merge(new_name.to_s => old_name.to_s)
attribute_method_matchers.each do |matcher|
matcher_new = matcher.method_name(new_name).to_s
matcher_old = matcher.method_name(old_name).to_s
define_proxy_call false, self, matcher_new, matcher_old
end
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 declares.
# define_attribute_methods :name, :age, :address
#
# private
#
# def clear_attribute(attr)
# ...
# end
# end
def define_attribute_methods(*attr_names)
attr_names.flatten.each { |attr_name| define_attribute_method(attr_name) }
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 declares.
# 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)
attribute_method_matchers.each do |matcher|
method_name = matcher.method_name(attr_name)
unless instance_method_already_implemented?(method_name)
generate_method = "define_method_#{matcher.method_missing_target}"
if respond_to?(generate_method, true)
send(generate_method, attr_name)
else
define_proxy_call true, generated_attribute_methods, method_name, matcher.method_missing_target, attr_name.to_s
end
end
end
attribute_method_matchers_cache.clear
end
# Removes all the previously dynamically defined methods from the class.
#
# class Person
# include ActiveModel::AttributeMethods
#
# attr_accessor :name
# attribute_method_suffix '_short?'
# define_attribute_method :name
#
# private
#
# def attribute_short?(attr)
# send(attr).length < 5
# end
# end
#
# person = Person.new
# person.name = 'Bob'
# person.name_short? # => true
#
# Person.undefine_attribute_methods
#
# person.name_short? # => NoMethodError
def undefine_attribute_methods
generated_attribute_methods.module_eval do
instance_methods.each { |m| undef_method(m) }
end
attribute_method_matchers_cache.clear
end
def generated_attribute_methods #:nodoc:
@generated_attribute_methods ||= Module.new {
extend Mutex_m
}.tap { |mod| include mod }
end
protected
def instance_method_already_implemented?(method_name) #:nodoc:
generated_attribute_methods.method_defined?(method_name)
end
private
# The methods +method_missing+ and +respond_to?+ of this module are
# invoked often in a typical rails, both of which invoke the method
# +match_attribute_method?+. The latter method iterates through an
# array doing regular expression matches, which results in a lot of
# object creations. Most of the times 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_matchers_cache #:nodoc:
@attribute_method_matchers_cache ||= ThreadSafe::Cache.new(initial_capacity: 4)
end
def attribute_method_matcher(method_name) #:nodoc:
attribute_method_matchers_cache.compute_if_absent(method_name) do
# Must try to match prefixes/suffixes first, or else the matcher with no prefix/suffix
# will match every time.
matchers = attribute_method_matchers.partition(&:plain?).reverse.flatten(1)
match = nil
matchers.detect { |method| match = method.match(method_name) }
match
end
end
# Define a method `name` in `mod` that dispatches to `send`
# using the given `extra` args. This fallbacks `define_method`
# and `send` if the given names cannot be compiled.
def define_proxy_call(include_private, mod, name, send, *extra) #:nodoc:
defn = if name =~ NAME_COMPILABLE_REGEXP
"def #{name}(*args)"
else
"define_method(:'#{name}') do |*args|"
end
extra = (extra.map!(&:inspect) << "*args").join(", ")
target = if send =~ CALL_COMPILABLE_REGEXP
"#{"self." unless include_private}#{send}(#{extra})"
else
"send(:'#{send}', #{extra})"
end
mod.module_eval <<-RUBY, __FILE__, __LINE__ + 1
#{defn}
#{target}
end
RUBY
end
class AttributeMethodMatcher #:nodoc:
attr_reader :prefix, :suffix, :method_missing_target
AttributeMethodMatch = Struct.new(:target, :attr_name, :method_name)
def initialize(options = {})
@prefix, @suffix = options.fetch(:prefix, ''), options.fetch(:suffix, '')
@regex = /^(?:#{Regexp.escape(@prefix)})(.*)(?:#{Regexp.escape(@suffix)})$/
@method_missing_target = "#{@prefix}attribute#{@suffix}"
@method_name = "#{prefix}%s#{suffix}"
end
def match(method_name)
if @regex =~ method_name
AttributeMethodMatch.new(method_missing_target, $1, method_name)
end
end
def method_name(attr_name)
@method_name % attr_name
end
def plain?
prefix.empty? && suffix.empty?
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 assigns 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, *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
# +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, *args, &block)
__send__(match.target, match.attr_name, *args, &block)
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
!match_attribute_method?(method.to_s).nil?
end
end
protected
def attribute_method?(attr_name) #:nodoc:
respond_to_without_attributes?(:attributes) && attributes.include?(attr_name)
end
private
# Returns a struct representing the matching attribute method.
# The struct's attributes are prefix, base and suffix.
def match_attribute_method?(method_name)
match = self.class.send(:attribute_method_matcher, method_name)
match if match && attribute_method?(match.attr_name)
end
def missing_attribute(attr_name, stack)
raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack
end
end
end
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