module ActiveRecord
module AttributeMethods #:nodoc:
DEFAULT_SUFFIXES = %w(= ? _before_type_cast)
def self.included(base)
base.extend ClassMethods
base.attribute_method_suffix *DEFAULT_SUFFIXES
end
# Declare and check for suffixed attribute methods.
module ClassMethods
# Declare 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 '_changed?'
#
# private
# def attribute_changed?(attr)
# ...
# end
# end
#
# person = Person.find(1)
# person.name_changed? # => false
# person.name = 'Hubert'
# person.name_changed? # => true
def attribute_method_suffix(*suffixes)
attribute_method_suffixes.concat suffixes
rebuild_attribute_method_regexp
end
# Returns MatchData if method_name is an attribute method.
def match_attribute_method?(method_name)
rebuild_attribute_method_regexp unless defined?(@@attribute_method_regexp) && @@attribute_method_regexp
@@attribute_method_regexp.match(method_name)
end
# Contains the names of the generated attribute methods.
def generated_methods #:nodoc:
@generated_methods ||= Set.new
end
def generated_methods?
!generated_methods.empty?
end
# generates all the attribute related methods for columns in the database
# accessors, mutators and query methods
def define_attribute_methods
return if generated_methods?
columns_hash.each do |name, column|
unless instance_methods.include?(name)
if self.serialized_attributes[name]
define_read_method_for_serialized_attribute(name)
else
define_read_method(name.to_sym, name, column)
end
end
unless instance_methods.include?("#{name}=")
define_write_method(name.to_sym)
end
unless instance_methods.include?("#{name}?")
define_question_method(name)
end
end
end
alias :define_read_methods :define_attribute_methods
private
# Suffixes a, ?, c become regexp /(a|\?|c)$/
def rebuild_attribute_method_regexp
suffixes = attribute_method_suffixes.map { |s| Regexp.escape(s) }
@@attribute_method_regexp = /(#{suffixes.join('|')})$/.freeze
end
# Default to =, ?, _before_type_cast
def attribute_method_suffixes
@@attribute_method_suffixes ||= []
end
# Define an attribute reader method. Cope with nil column.
def define_read_method(symbol, attr_name, column)
cast_code = column.type_cast_code('v') if column
access_code = cast_code ? "(v=@attributes['#{attr_name}']) && #{cast_code}" : "@attributes['#{attr_name}']"
unless attr_name.to_s == self.primary_key.to_s
access_code = access_code.insert(0, "missing_attribute('#{attr_name}', caller) unless @attributes.has_key?('#{attr_name}'); ")
end
evaluate_attribute_method attr_name, "def #{symbol}; @attributes_cache['#{attr_name}'] ||= begin; #{access_code}; end; end"
end
# Define read method for serialized attribute.
def define_read_method_for_serialized_attribute(attr_name)
evaluate_attribute_method attr_name, "def #{attr_name}; unserialize_attribute('#{attr_name}'); end"
end
# Define an attribute ? method.
def define_question_method(attr_name)
evaluate_attribute_method attr_name, "def #{attr_name}?; query_attribute('#{attr_name}'); end", "#{attr_name}?"
end
def define_write_method(attr_name)
evaluate_attribute_method attr_name, "def #{attr_name}=(new_value);write_attribute('#{attr_name}', new_value);end", "#{attr_name}="
end
# Evaluate the definition for an attribute related method
def evaluate_attribute_method(attr_name, method_definition, method_name=attr_name)
unless method_name.to_s == primary_key.to_s
generated_methods << method_name
end
begin
class_eval(method_definition)
rescue SyntaxError => err
generated_methods.delete(attr_name)
if logger
logger.warn "Exception occurred during reader method compilation."
logger.warn "Maybe #{attr_name} is not a valid Ruby identifier?"
logger.warn "#{err.message}"
end
end
end
end # ClassMethods
# Allows access to the object attributes, which are held in the @attributes hash, as were
# they 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 we haven't generated any methods yet, generate them, then
# see if we've created the method we're looking for.
if !self.class.generated_methods?
self.class.define_attribute_methods
if self.class.generated_methods.include?(method_name)
return self.send(method_id, *args, &block)
end
end
if self.class.primary_key.to_s == method_name
id
elsif md = self.class.match_attribute_method?(method_name)
attribute_name, method_type = md.pre_match, md.to_s
if @attributes.include?(attribute_name)
__send__("attribute#{method_type}", attribute_name, *args, &block)
else
super
end
elsif @attributes.include?(method_name)
read_attribute(method_name)
else
super
end
end
# Returns the value of the attribute identified by <tt>attr_name</tt> after it has been typecast (for example,
# "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)).
def read_attribute(attr_name)
attr_name = attr_name.to_s
if !(value = @attributes[attr_name]).nil?
if column = column_for_attribute(attr_name)
if unserializable_attribute?(attr_name, column)
unserialize_attribute(attr_name)
else
column.type_cast(value)
end
else
value
end
else
nil
end
end
def read_attribute_before_type_cast(attr_name)
@attributes[attr_name]
end
# Returns true if the attribute is of a text column and marked for serialization.
def unserializable_attribute?(attr_name, column)
column.text? && self.class.serialized_attributes[attr_name]
end
# Returns the unserialized object of the attribute.
def unserialize_attribute(attr_name)
unserialized_object = object_from_yaml(@attributes[attr_name])
if unserialized_object.is_a?(self.class.serialized_attributes[attr_name]) || unserialized_object.nil?
@attributes[attr_name] = unserialized_object
else
raise SerializationTypeMismatch,
"#{attr_name} was supposed to be a #{self.class.serialized_attributes[attr_name]}, but was a #{unserialized_object.class.to_s}"
end
end
# Updates the attribute identified by <tt>attr_name</tt> with the specified +value+. Empty strings for fixnum and float
# columns are turned into nil.
def write_attribute(attr_name, value)
attr_name = attr_name.to_s
@attributes_cache.delete(attr_name)
if (column = column_for_attribute(attr_name)) && column.number?
@attributes[attr_name] = convert_number_column_value(value)
else
@attributes[attr_name] = value
end
end
def query_attribute(attr_name)
unless value = read_attribute(attr_name)
false
else
column = self.class.columns_hash[attr_name]
if column.nil?
if Numeric === value || value !~ /[^0-9]/
!value.to_i.zero?
else
!value.blank?
end
elsif column.number?
!value.zero?
else
!value.blank?
end
end
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_priv = false)
method_name = method.to_s
if super
return true
elsif !self.class.generated_methods?
self.class.define_attribute_methods
if self.class.generated_methods.include?(method_name)
return true
end
end
if @attributes.nil?
return super
elsif @attributes.include?(method_name)
return true
elsif md = self.class.match_attribute_method?(method_name)
return true if @attributes.include?(md.pre_match)
end
super
end
private
def missing_attribute(attr_name, stack)
raise ActiveRecord::MissingAttributeError, "missing attribute: #{attr_name}", stack
end
# Handle *? for method_missing.
def attribute?(attribute_name)
query_attribute(attribute_name)
end
# Handle *= for method_missing.
def attribute=(attribute_name, value)
write_attribute(attribute_name, value)
end
# Handle *_before_type_cast for method_missing.
def attribute_before_type_cast(attribute_name)
read_attribute_before_type_cast(attribute_name)
end
end
end
