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 <tt>respond_to?</tt> to rewrite the method.
#
# #{prefix}#{attr}(*args, &block)
#
# to
#
# #{prefix}attribute(#{attr}, *args, &block)
#
# An <tt>#{prefix}attribute</tt> 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 <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.
#
# 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 <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.
#
# 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
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
@attribute_methods_generated = true
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:
@@attribute_method_matchers ||= []
end
end
# Allows access to the object attributes, which are held in the <tt>@attributes</tt> 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)
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 <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
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
