require 'active_support/core_ext/hash/keys' require 'active_support/core_ext/class/inheritable_attributes' module ActiveModel class MissingAttributeError < NoMethodError end module AttributeMethods extend ActiveSupport::Concern # Declare and check for suffixed attribute methods. module ClassMethods # Defines an "attribute" method (like +inheritance_column+ or # +table_name+). A new (class) method will be created with the # given name. If a value is specified, the new method will # return that value (as a string). Otherwise, the given block # will be used to compute the value of the method. # # The original method will be aliased, with the new name being # prefixed with "original_". This allows the new method to # access the original value. # # Example: # # class A < ActiveRecord::Base # define_attr_method :primary_key, "sysid" # define_attr_method( :inheritance_column ) do # original_inheritance_column + "_id" # end # end def define_attr_method(name, value=nil, &block) sing = metaclass sing.send :alias_method, "original_#{name}", name if block_given? sing.send :define_method, name, &block else # use eval instead of a block to work around a memory leak in dev # mode in fcgi sing.class_eval "def #{name}; #{value.to_s.inspect}; end" end 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 #{prefix}attribute instance method must exist and accept at least # the +attr+ argument. # # For example: # # class Person < ActiveRecord::Base # attribute_method_prefix 'clear_' # # private # def clear_attribute(attr) # ... # end # end # # person = Person.find(1) # person.name # => 'Gem' # person.clear_name # person.name # => '' def attribute_method_prefix(*prefixes) attribute_method_matchers.concat(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 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. # # For example: # # class Person < ActiveRecord::Base # attribute_method_suffix '_short?' # # private # def attribute_short?(attr) # ... # end # end # # person = Person.find(1) # person.name # => 'Gem' # person.name_short? # => true def attribute_method_suffix(*suffixes) attribute_method_matchers.concat(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 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. # # For example: # # class Person < ActiveRecord::Base # attribute_method_affix :prefix => 'reset_', :suffix => '_to_default!' # # private # def reset_attribute_to_default!(attr) # ... # end # end # # person = Person.find(1) # person.name # => 'Gem' # person.reset_name_to_default! # person.name # => 'Gemma' def attribute_method_affix(*affixes) attribute_method_matchers.concat(affixes.map { |affix| AttributeMethodMatcher.new :prefix => affix[:prefix], :suffix => affix[:suffix] }) undefine_attribute_methods end def alias_attribute(new_name, old_name) attribute_method_matchers.each do |matcher| module_eval <<-STR, __FILE__, __LINE__+1 def #{matcher.method_name(new_name)}(*args) send(:#{matcher.method_name(old_name)}, *args) end STR end end def define_attribute_methods(attr_names) return if attribute_methods_generated? attr_names.each do |attr_name| attribute_method_matchers.each do |matcher| unless instance_method_already_implemented?(matcher.method_name(attr_name)) generate_method = "define_method_#{matcher.prefix}attribute#{matcher.suffix}" if respond_to?(generate_method) send(generate_method, attr_name) else generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__+1 def #{matcher.method_name(attr_name)}(*args) send(:#{matcher.method_missing_target}, '#{attr_name}', *args) end STR end end end end @attribute_methods_generated = true end def undefine_attribute_methods generated_attribute_methods.module_eval do instance_methods.each { |m| undef_method(m) } end @attribute_methods_generated = nil end def generated_attribute_methods #:nodoc: @generated_attribute_methods ||= begin mod = Module.new include mod mod end end def attribute_methods_generated? @attribute_methods_generated ||= nil end protected def instance_method_already_implemented?(method_name) method_defined?(method_name) end private class AttributeMethodMatcher attr_reader :prefix, :suffix AttributeMethodMatch = Struct.new(:target, :attr_name) def initialize(options = {}) options.symbolize_keys! @prefix, @suffix = options[:prefix] || '', options[:suffix] || '' @regex = /^(#{Regexp.escape(@prefix)})(.+?)(#{Regexp.escape(@suffix)})$/ end def match(method_name) if matchdata = @regex.match(method_name) AttributeMethodMatch.new(method_missing_target, matchdata[2]) else nil end end def method_name(attr_name) "#{prefix}#{attr_name}#{suffix}" end def method_missing_target :"#{prefix}attribute#{suffix}" end end def attribute_method_matchers #:nodoc: read_inheritable_attribute(:attribute_method_matchers) || write_inheritable_attribute(:attribute_method_matchers, []) end end # Allows access to the object attributes, which are held in the @attributes hash, as though they # were first-class methods. So a Person class with a name attribute can use Person#name and # Person#name= and never directly use the attributes hash -- except for multiple assigns with # ActiveRecord#attributes=. A Milestone class can also ask Milestone#completed? to test that # the completed attribute is not +nil+ or 0. # # 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. def method_missing(method_id, *args, &block) if method_id == :to_ary || method_id == :to_str raise NoMethodError, "undefined method `#{method_id}' for #{inspect}:#{self.class}" end method_name = method_id.to_s if match = match_attribute_method?(method_name) guard_private_attribute_method!(method_name, args) return __send__(match.target, match.attr_name, *args, &block) end super end # A Person object with a name attribute can ask person.respond_to?(:name), # person.respond_to?(:name=), and person.respond_to?(:name?) # which will all return +true+. alias :respond_to_without_attributes? :respond_to? def respond_to?(method, include_private_methods = false) if super return 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 given method is private. return false elsif match_attribute_method?(method.to_s) return true end super end protected def attribute_method?(attr_name) 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) self.class.send(:attribute_method_matchers).each do |method| if (match = method.match(method_name)) && attribute_method?(match.attr_name) return match end end nil end # prevent method_missing from calling private methods with #send def guard_private_attribute_method!(method_name, args) if self.class.private_method_defined?(method_name) raise NoMethodError.new("Attempt to call private method", method_name, args) end end def missing_attribute(attr_name, stack) raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack end end end