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require 'active_record/support/class_attribute_accessors'
require 'active_record/support/class_inheritable_attributes'
require 'active_record/support/inflector'
require 'yaml'
unless Object.respond_to?(:require_association)
Object.send(:define_method, :require_association) { |file_name| ActiveRecord::Base.require_association(file_name) }
module ActiveRecord #:nodoc:
class ActiveRecordError < StandardError #:nodoc:
class AssociationTypeMismatch < ActiveRecordError #:nodoc:
class SerializationTypeMismatch < ActiveRecordError #:nodoc:
class AdapterNotSpecified < ActiveRecordError # :nodoc:
class AdapterNotFound < ActiveRecordError # :nodoc:
class ConnectionNotEstablished < ActiveRecordError #:nodoc:
class ConnectionFailed < ActiveRecordError #:nodoc:
class RecordNotFound < ActiveRecordError #:nodoc:
class StatementInvalid < ActiveRecordError #:nodoc:
# Active Record objects doesn't specify their attributes directly, but rather infer them from the table definition with
# which they're linked. Adding, removing, and changing attributes and their type is done directly in the database. Any change
# is instantly reflected in the Active Record objects. The mapping that binds a given Active Record class to a certain
# database table will happen automatically in most common cases, but can be overwritten for the uncommon ones.
# See the mapping rules in table_name and the full example in link:files/README.html for more insight.
# == Creation
# Active Records accepts constructor parameters either in a hash or as a block. The hash method is especially useful when
# you're receiving the data from somewhere else, like a HTTP request. It works like this:
# user ="name" => "David", "occupation" => "Code Artist")
# # => "David"
# You can also use block initialization:
# user = do |u|
# = "David"
# u.occupation = "Code Artist"
# end
# And of course you can just create a bare object and specify the attributes after the fact:
# user =
# = "David"
# user.occupation = "Code Artist"
# == Conditions
# Conditions can either be specified as a string or an array representing the WHERE-part of an SQL statement.
# The array form is to be used when the condition input is tainted and requires sanitization. The string form can
# be used for statements that doesn't involve tainted data. Examples:
# User < ActiveRecord::Base
# def self.authenticate_unsafely(user_name, password)
# find_first("user_name = '#{user_name}' AND password = '#{password}'")
# end
# def self.authenticate_safely(user_name, password)
# find_first([ "user_name = '%s' AND password = '%s'", user_name, password ])
# end
# end
# The +authenticate_unsafely+ method inserts the parameters directly into the query and is thus susceptible to SQL-injection
# attacks if the +user_name+ and +password+ parameters come directly from a HTTP request. The +authenticate_safely+ method, on
# the other hand, will sanitize the +user_name+ and +password+ before inserting them in the query, which will ensure that
# an attacker can't escape the query and fake the login (or worse).
# == Overwriting default accessors
# All column values are automatically available through basic accessors on the Active Record object, but some times you
# want to specialize this behavior. This can be done by either by overwriting the default accessors (using the same
# name as the attribute) calling read_attribute(attr_name) and write_attribute(attr_name, value) to actually change things.
# Example:
# class Song < ActiveRecord::Base
# # Uses an integer of seconds to hold the length of the song
# def length=(minutes)
# write_attribute("length", minutes * 60)
# end
# def length
# read_attribute("length") / 60
# end
# end
# == Saving arrays, hashes, and other non-mappeable objects in text columns
# Active Record can serialize any object in text columns using YAML. To do so, you must specify this with a call to the class method +serialize+.
# This makes it possible to store arrays, hashes, and other non-mappeable objects without doing any additional work. Example:
# class User < ActiveRecord::Base
# serialize :preferences
# end
# user = User.create("preferences" => { "background" => "black", "display" => large })
# User.find( # => { "background" => "black", "display" => large }
# You can also specify an optional :class_name option that'll raise an exception if a serialized object is retrieved as a
# descendent of a class not in the hierarchy. Example:
# class User < ActiveRecord::Base
# serialize :preferences, :class_name => "Hash"
# end
# user = User.create("preferences" => %w( one two three ))
# User.find( # raises SerializationTypeMismatch
# == Single table inheritance
# Active Record allows inheritance by storing the name of the class in a column that by default is called "type" (can be changed
# by overwriting <tt>Base.inheritance_column</tt>). This means that an inheritance looking like this:
# class Company < ActiveRecord::Base; end
# class Firm < Company; end
# class Client < Company; end
# class PriorityClient < Client; end
# When you do Firm.create("name" => "37signals"), this record with be saved in the companies table with type = "Firm". You can then
# fetch this row again using Company.find_first "name = '37signals'" and it will return a Firm object.
# Note, all the attributes for all the cases are kept in the same table. Read more:
# == Connection to multiple databases in different models
# Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection.
# All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection.
# For example, if Course is a ActiveRecord::Base, but resides in a different database you can just say Course.establish_connection
# and Course *and all its subclasses* will use this connection instead.
# This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is
# requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.
# == Exceptions
# * +ActiveRecordError+ -- generic error class and superclass of all other errors raised by Active Record
# * +AdapterNotSpecified+ -- the configuration hash used in <tt>establish_connection</tt> didn't include a
# <tt>:adapter</tt> key.
# * +AdapterNotSpecified+ -- the <tt>:adapter</tt> key used in <tt>establish_connection</tt> specified an unexisting adapter
# (or a bad spelling of an existing one).
# * +AssociationTypeMismatch+ -- the object assigned to the association wasn't of the type specified in the association definition.
# * +SerializationTypeMismatch+ -- the object serialized wasn't of the class specified in the <tt>:class_name</tt> option of
# the serialize definition.
# * +ConnectionNotEstablished+ -- no connection has been established. Use <tt>establish_connection</tt> before querying.
# * +RecordNotFound+ -- no record responded to the find* method.
# Either the row with the given ID doesn't exist or the row didn't meet the additional restrictions.
# * +StatementInvalid+ -- the database server rejected the SQL statement. The precise error is added in the message.
# Either the record with the given ID doesn't exist or the record didn't meet the additional restrictions.
# *Note*: The attributes listed are class-level attributes (accessible from both the class and instance level).
# So it's possible to assign a logger to the class through Base.logger= which will then be used by all
# instances in the current object space.
class Base
include ClassInheritableAttributes
# Accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then passed
# on to any new database connections made and which can be retrieved on both a class and instance level by calling +logger+.
cattr_accessor :logger
# Returns the connection currently associated with the class. This can
# also be used to "borrow" the connection to do database work unrelated
# to any of the specific Active Records.
def self.connection
# Returns the connection currently associated with the class. This can
# also be used to "borrow" the connection to do database work that isn't
# easily done without going straight to SQL.
def connection
def self.inherited(child) #:nodoc:
@@subclasses[self] ||= []
@@subclasses[self] << child
@@subclasses = {}
cattr_accessor :configurations
@@primary_key_prefix_type = {}
# Accessor for the prefix type that will be prepended to every primary key column name. The options are :table_name and
# :table_name_with_underscore. If the first is specified, the Product class will look for "productid" instead of "id" as
# the primary column. If the latter is specified, the Product class will look for "product_id" instead of "id". Remember
# that this is a global setting for all Active Records.
cattr_accessor :primary_key_prefix_type
@@primary_key_prefix_type = nil
# Accessor for the name of the prefix string to prepend to every table name. So if set to "basecamp_", all
# table names will be named like "basecamp_projects", "basecamp_people", etc. This is a convinient way of creating a namespace
# for tables in a shared database. By default, the prefix is the empty string.
cattr_accessor :table_name_prefix
@@table_name_prefix = ""
# Works like +table_name_prefix+, but appends instead of prepends (set to "_basecamp" gives "projects_basecamp",
# "people_basecamp"). By default, the suffix is the empty string.
cattr_accessor :table_name_suffix
@@table_name_suffix = ""
# Indicate whether or not table names should be the pluralized versions of the corresponding class names.
# If true, this the default table name for a +Product+ class will be +products+. If false, it would just be +product+.
# See table_name for the full rules on table/class naming. This is true, by default.
cattr_accessor :pluralize_table_names
@@pluralize_table_names = true
# When turned on (which is default), all associations are included using "load". This mean that any change is instant in cached
# environments like mod_ruby or FastCGI. When set to false, "require" is used, which is faster but requires server restart to
# be effective.
@@reload_associations = true
cattr_accessor :reload_associations
@@associations_loaded = []
cattr_accessor :associations_loaded
class << self # Class methods
# Returns objects for the records responding to either a specific id (1), a list of ids (1, 5, 6) or an array of ids.
# If only one ID is specified, that object is returned directly. If more than one ID is specified, an array is returned.
# Examples:
# Person.find(1) # returns the object for ID = 1
# Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
# Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
# +RecordNotFound+ is raised if no record can be found.
def find(*ids)
ids = ids.flatten.compact.uniq
if ids.length > 1
ids_list ={ |id| "'#{sanitize(id)}'" }.join(", ")
objects = find_all("#{primary_key} IN (#{ids_list})", primary_key)
if objects.length == ids.length
return objects
raise RecordNotFound, "Couldn't find #{name} with ID in (#{ids_list})"
elsif ids.length == 1
id = ids.first
sql = "SELECT * FROM #{table_name} WHERE #{primary_key} = '#{sanitize(id)}'"
sql << " AND #{type_condition}" unless descends_from_active_record?
if record = connection.select_one(sql, "#{name} Find")
raise RecordNotFound, "Couldn't find #{name} with ID = #{id}"
raise RecordNotFound, "Couldn't find #{name} without an ID"
# Works like find, but the record matching +id+ must also meet the +conditions+.
# +RecordNotFound+ is raised if no record can be found matching the +id+ or meeting the condition.
# Example:
# Person.find_on_conditions 5, "first_name LIKE '%dav%' AND last_name = 'heinemeier'"
def find_on_conditions(id, conditions)
find_first("#{primary_key} = '#{sanitize(id)}' AND #{sanitize_conditions(conditions)}") ||
raise(RecordNotFound, "Couldn't find #{name} with #{primary_key} = #{id} on the condition of #{conditions}")
# Returns an array of all the objects that could be instantiated from the associated
# table in the database. The +conditions+ can be used to narrow the selection of objects (WHERE-part),
# such as by "color = 'red'", and arrangement of the selection can be done through +orderings+ (ORDER BY-part),
# such as by "last_name, first_name DESC". A maximum of returned objects can be specified in +limit+. Example:
# Project.find_all "category = 'accounts'", "last_accessed DESC", 15
def find_all(conditions = nil, orderings = nil, limit = nil, joins = nil)
sql = "SELECT * FROM #{table_name} "
sql << "#{joins} " if joins
add_conditions!(sql, conditions)
sql << "ORDER BY #{orderings} " unless orderings.nil?
sql << "LIMIT #{limit} " unless limit.nil?
# Works like find_all, but requires a complete SQL string. Example:
# Post.find_by_sql "SELECT p.*, FROM posts p, comments c WHERE = c.post_id"
def find_by_sql(sql)
connection.select_all(sql, "#{name} Load").inject([]) { |objects, record| objects << instantiate(record) }
# Returns the object for the first record responding to the conditions in +conditions+,
# such as "group = 'master'". If more than one record is returned from the query, it's the first that'll
# be used to create the object. In such cases, it might be beneficial to also specify
# +orderings+, like "income DESC, name", to control exactly which record is to be used. Example:
# Employee.find_first "income > 50000", "income DESC, name"
def find_first(conditions = nil, orderings = nil)
sql = "SELECT * FROM #{table_name} "
add_conditions!(sql, conditions)
sql << "ORDER BY #{orderings} " unless orderings.nil?
sql << "LIMIT 1"
record = connection.select_one(sql, "#{name} Load First")
instantiate(record) unless record.nil?
# Creates an object, instantly saves it as a record (if the validation permits it), and returns it. If the save
# fail under validations, the unsaved object is still returned.
def create(attributes = nil)
object = new(attributes)
# Finds the record from the passed +id+, instantly saves it with the passed +attributes+ (if the validation permits it),
# and returns it. If the save fail under validations, the unsaved object is still returned.
def update(id, attributes)
object = find(id)
object.attributes = attributes
# Updates all records with the SET-part of an SQL update statement in +updates+. A subset of the records can be selected
# by specifying +conditions+. Example:
# Billing.update_all "category = 'authorized', approved = 1", "author = 'David'"
def update_all(updates, conditions = nil)
sql = "UPDATE #{table_name} SET #{updates} "
add_conditions!(sql, conditions)
connection.update(sql, "#{name} Update")
# Destroys the objects for all the records that matches the +condition+ by instantiating each object and calling
# the destroy method. Example:
# Person.destroy_all "last_login < '2004-04-04'"
def destroy_all(conditions = nil)
find_all(conditions).each { |object| object.destroy }
# Deletes all the records that matches the +condition+ without instantiating the objects first (and hence not
# calling the destroy method). Example:
# Post.destroy_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"
def delete_all(conditions = nil)
sql = "DELETE FROM #{table_name} "
add_conditions!(sql, conditions)
connection.delete(sql, "#{name} Delete all")
# Returns the number of records that meets the +conditions+. Zero is returned if no records match. Example:
# Product.count "sales > 1"
def count(conditions = nil)
sql = "SELECT COUNT(*) FROM #{table_name} "
add_conditions!(sql, conditions)
# Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part.
# Product.count "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id ="
def count_by_sql(sql)
count = connection.select_one(sql, "#{name} Count").values.first
return count ? count.to_i : 0
# Increments the specified counter by one. So <tt>DiscussionBoard.increment_counter("post_count",
# discussion_board_id)</tt> would increment the "post_count" counter on the board responding to discussion_board_id.
# This is used for caching aggregate values, so that they doesn't need to be computed every time. Especially important
# for looping over a collection where each element require a number of aggregate values. Like the DiscussionBoard
# that needs to list both the number of posts and comments.
def increment_counter(counter_name, id)
update_all "#{counter_name} = #{counter_name} + 1", "#{primary_key} = #{id}"
# Works like increment_counter, but decrements instead.
def decrement_counter(counter_name, id)
update_all "#{counter_name} = #{counter_name} - 1", "#{primary_key} = #{id}"
# Attributes named in this macro are protected from mass-assignment, such as <tt>new(attributes)</tt> and
# <tt>attributes=(attributes)</tt>. Their assignment will simply be ignored. Instead, you can use the direct writer
# methods to do assignment. This is meant to protect sensitive attributes to be overwritten by URL/form hackers. Example:
# class Customer < ActiveRecord::Base
# attr_protected :credit_rating
# end
# customer ="name" => David, "credit_rating" => "Excellent")
# customer.credit_rating # => nil
# customer.attributes = { "description" => "Jolly fellow", "credit_rating" => "Superb" }
# customer.credit_rating # => nil
# customer.credit_rating = "Average"
# customer.credit_rating # => "Average"
def attr_protected(*attributes)
write_inheritable_array("attr_protected", attributes)
# Returns an array of all the attributes that have been protected from mass-assigment.
def protected_attributes # :nodoc:
# If this macro is used, only those attributed named in it will be accessible for mass-assignment, such as
# <tt>new(attributes)</tt> and <tt>attributes=(attributes)</tt>. This is the more conservative choice for mass-assignment
# protection. If you'd rather start from an all-open default and restrict attributes as needed, have a look at
# attr_protected.
def attr_accessible(*attributes)
write_inheritable_array("attr_accessible", attributes)
# Returns an array of all the attributes that have been made accessible to mass-assigment.
def accessible_attributes # :nodoc:
# Specifies that the attribute by the name of +attr_name+ should be serialized before saving to the database and unserialized
# after loading from the database. The serialization is done through YAML. If +class_name+ is specified, the serialized
# object must be of that class on retrival or +SerializationTypeMismatch+ will be raised.
def serialize(attr_name, class_name = Object)
write_inheritable_attribute("attr_serialized", serialized_attributes.update(attr_name.to_s => class_name))
# Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.
def serialized_attributes
read_inheritable_attribute("attr_serialized") || { }
# Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending
# directly from ActiveRecord. So if the hierarchy looks like: Reply < Message < ActiveRecord, then Message is used
# to guess the table name from even when called on Reply. The guessing rules are as follows:
# * Class name ends in "x", "ch" or "ss": "es" is appended, so a Search class becomes a searches table.
# * Class name ends in "y" preceded by a consonant or "qu": The "y" is replaced with "ies", so a Category class becomes a categories table.
# * Class name ends in "fe": The "fe" is replaced with "ves", so a Wife class becomes a wives table.
# * Class name ends in "lf" or "rf": The "f" is replaced with "ves", so a Half class becomes a halves table.
# * Class name ends in "person": The "person" is replaced with "people", so a Salesperson class becomes a salespeople table.
# * Class name ends in "man": The "man" is replaced with "men", so a Spokesman class becomes a spokesmen table.
# * Class name ends in "sis": The "i" is replaced with an "e", so a Basis class becomes a bases table.
# * Class name ends in "tum" or "ium": The "um" is replaced with an "a", so a Datum class becomes a data table.
# * Class name ends in "child": The "child" is replaced with "children", so a NodeChild class becomes a node_children table.
# * Class name ends in an "s": No additional characters are added or removed.
# * Class name doesn't end in "s": An "s" is appended, so a Comment class becomes a comments table.
# * Class name with word compositions: Compositions are underscored, so CreditCard class becomes a credit_cards table.
# Additionally, the class-level table_name_prefix is prepended to the table_name and the table_name_suffix is appended.
# So if you have "myapp_" as a prefix, the table name guess for an Account class becomes "myapp_accounts".
# You can also overwrite this class method to allow for unguessable links, such as a Mouse class with a link to a
# "mice" table. Example:
# class Mouse < ActiveRecord::Base
# def self.table_name() "mice" end
# end
def table_name(class_name = nil)
if class_name.nil?
class_name = class_name_of_active_record_descendant(self)
table_name_prefix + undecorated_table_name(class_name) + table_name_suffix
table_name_prefix + undecorated_table_name(class_name) + table_name_suffix
# Defines the primary key field -- can be overridden in subclasses. Overwritting will negate any effect of the
# primary_key_prefix_type setting, though.
def primary_key
case primary_key_prefix_type
when :table_name
Inflector.foreign_key(class_name_of_active_record_descendant(self), false)
when :table_name_with_underscore
# Defines the column name for use with single table inheritance -- can be overridden in subclasses.
def inheritance_column
# Turns the +table_name+ back into a class name following the reverse rules of +table_name+.
def class_name(table_name = table_name) # :nodoc:
# remove any prefix and/or suffix from the table name
class_name = Inflector.camelize(table_name[table_name_prefix.length..-(table_name_suffix.length + 1)])
class_name = Inflector.singularize(class_name) if pluralize_table_names
return class_name
# Returns an array of column objects for the table associated with this class.
def columns
@columns ||= connection.columns(table_name, "#{name} Columns")
# Returns an array of column objects for the table associated with this class.
def columns_hash
@columns_hash ||= columns.inject({}) { |hash, column| hash[] = column; hash }
# Returns an array of columns objects where the primary id, all columns ending in "_id" or "_count",
# and columns used for single table inheritance has been removed.
def content_columns
@content_columns ||= columns.reject { |c| == primary_key || =~ /(_id|_count)$/ || == inheritance_column }
# Returns a hash of all the methods added to query each of the columns in the table with the name of the method as the key
# and true as the value. This makes it possible to do O(1) lookups in respond_to? to check if a given method for attribute
# is available.
def column_methods_hash
@dynamic_methods_hash ||= columns_hash.keys.inject( do |methods, attr|
methods[attr.to_sym] = true
methods["#{attr}=".to_sym] = true
methods["#{attr}?".to_sym] = true
# Transforms attribute key names into a more humane format, such as "First name" instead of "first_name". Example:
# Person.human_attribute_name("first_name") # => "First name"
def human_attribute_name(attribute_key_name)
attribute_key_name.gsub(/_/, " ").capitalize unless attribute_key_name.nil?
def descends_from_active_record? # :nodoc:
superclass == Base
# Used to sanitize objects before they're used in an SELECT SQL-statement.
def sanitize(object) # :nodoc:
return object if Fixnum === object
object.to_s.gsub(/([;:])/, "").gsub('##', '\#\#').gsub(/'/, "''") # ' (for ruby-mode)
# Used to aggregate logging and benchmark, so you can measure and represent multiple statements in a single block.
# Usage (hides all the SQL calls for the individual actions and calculates total runtime for them all):
# Project.benchmark("Creating project") do
# project = Project.create("name" => "stuff")
# project.create_manager("name" => "David")
# project.milestones << Milestone.find_all
# end
def benchmark(title)
result = nil
logger.level = Logger::ERROR
bm = Benchmark.measure { result = yield }
logger.level = Logger::DEBUG "#{title} (#{sprintf("%f", bm.real)})"
return result
# Loads the <tt>file_name</tt> if reload_associations is true or requires if it's false.
def require_association(file_name)
if !associations_loaded.include?(file_name)
associations_loaded << file_name
reload_associations ? silence_warnings { load("#{file_name}.rb") } : require(file_name)
# Resets the list of dependencies loaded (typically to be called by the end of a request), so when require_association is
# called for that dependency it'll be loaded anew.
def reset_associations_loaded
associations_loaded = []
# Finder methods must instantiate through this method to work with the single-table inheritance model
# that makes it possible to create objects of different types from the same table.
def instantiate(record)
object = record_with_type?(record) ? compute_type(record[inheritance_column]).allocate : allocate
object.instance_variable_set("@attributes", record)
return object
# Returns true if the +record+ has a single table inheritance column and is using it.
def record_with_type?(record)
record.include?(inheritance_column) && !record[inheritance_column].nil? &&
# Returns the name of the type of the record using the current module as a prefix. So descendents of
# MyApp::Business::Account would be appear as "MyApp::Business::AccountSubclass".
def type_name_with_module(type_name) =~ /::/ ?*)::/).first.first + "::" + type_name : type_name
# Adds a sanitized version of +conditions+ to the +sql+ string. Note that it's the passed +sql+ string is changed.
def add_conditions!(sql, conditions)
sql << "WHERE #{sanitize_conditions(conditions)} " unless conditions.nil?
sql << (conditions.nil? ? "WHERE " : " AND ") + type_condition unless descends_from_active_record?
def type_condition
" (" + subclasses.inject("#{inheritance_column} = '#{Inflector.demodulize(name)}' ") do |condition, subclass|
condition << "OR #{inheritance_column} = '#{Inflector.demodulize(}'"
end + ") "
# Guesses the table name, but does not decorate it with prefix and suffix information.
def undecorated_table_name(class_name = class_name_of_active_record_descendant(self))
table_name = Inflector.underscore(Inflector.demodulize(class_name))
table_name = Inflector.pluralize(table_name) if pluralize_table_names
return table_name
def subclasses
@@subclasses[self] ||= []
@@subclasses[self] + extra = @@subclasses[self].inject([]) {|list, subclass| list + subclass.subclasses }
# Returns the class type of the record using the current module as a prefix. So descendents of
# MyApp::Business::Account would be appear as MyApp::Business::AccountSubclass.
def compute_type(type_name)
type_name_with_module(type_name).split("::").inject(Object) do |final_type, part|
final_type = final_type.const_get(part)
# Returns the name of the class descending directly from ActiveRecord in the inheritance hierarchy.
def class_name_of_active_record_descendant(klass)
if klass.superclass == Base
elsif klass.superclass.nil?
raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
# Accepts either a condition array or string. The string is returned untouched, but the array has each of
# the condition values sanitized.
def sanitize_conditions(conditions)
if Array === conditions
statement, values = conditions[0], conditions[1..-1]
values.collect! { |value| sanitize(value) }
conditions = statement % values
return conditions
# New objects can be instantiated as either empty (pass no construction parameter) or pre-set with
# attributes but not yet saved (pass a hash with key names matching the associated table column names).
# In both instances, valid attribute keys are determined by the column names of the associated table --
# hence you can't have attributes that aren't part of the table columns.
def initialize(attributes = nil)
@attributes = attributes_from_column_definition
@new_record = true
self.attributes = attributes unless attributes.nil?
yield self if block_given?
# Every Active Record class must use "id" as their primary ID. This getter overwrites the native
# id method, which isn't being used in this context.
def id
# Sets the primary ID.
def id=(value)
write_attribute(self.class.primary_key, value)
# Returns true if this object hasn't been saved yet -- that is, a record for the object doesn't exist yet.
def new_record?
# * No record exists: Creates a new record with values matching those of the object attributes.
# * A record does exist: Updates the record with values matching those of the object attributes.
def save
return true
# Deletes the record in the database and freezes this instance to reflect that no changes should
# be made (since they can't be persisted).
def destroy
unless new_record?
"DELETE FROM #{self.class.table_name} " +
"WHERE #{self.class.primary_key} = '#{id}'",
"#{} Destroy"
# Returns a clone of the record that hasn't been assigned an id yet and is treated as a new record.
def clone
attr =
self.attribute_names.each do |name|
attr[name] = read_attribute(name).clone
rescue TypeError
attr[name] = read_attribute(name)
cloned_record =
cloned_record.instance_variable_set "@new_record", true = nil
# Updates a single attribute and saves the record. This is especially useful for boolean flags on existing records.
def update_attribute(name, value)
self[name] = value
# Returns the value of attribute identified by <tt>attr_name</tt> after it has been type cast (for example,
# "2004-12-12" in a data column is cast to a date object, like, 12, 12)).
# (Alias for the protected read_attribute method).
def [](attr_name)
# Updates the attribute identified by <tt>attr_name</tt> with the specified +value+.
# (Alias for the protected write_attribute method).
def []= (attr_name, value)
write_attribute(attr_name, value)
# Allows you to set all the attributes at once by passing in a hash with keys
# matching the attribute names (which again matches the column names). Sensitive attributes can be protected
# from this form of mass-assignment by using the +attr_protected+ macro. Or you can alternatively
# specify which attributes *can* be accessed in with the +attr_accessible+ macro. Then all the
# attributes not included in that won't be allowed to be mass-assigned.
def attributes=(attributes)
return if attributes.nil?
multi_parameter_attributes = []
remove_attributes_protected_from_mass_assignment(attributes).each do |k, v|
k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
# Returns true if the specified +attribute+ has been set by the user or by a database load and is neither
# nil nor empty? (the latter only applies to objects that responds to empty?, most notably Strings).
def attribute_present?(attribute)
is_empty = read_attribute(attribute).respond_to?("empty?") ? read_attribute(attribute).empty? : false
@attributes.include?(attribute) && !@attributes[attribute].nil? && !is_empty
# Returns an array of names for the attributes available on this object sorted alphabetically.
def attribute_names
# Returns the column object for the named attribute.
def column_for_attribute(name)
# Returns true if the +comparison_object+ is of the same type and has the same id.
def ==(comparison_object)
comparison_object.instance_of?(self.class) && == id
# Delegates to ==
def eql?(comparison_object)
self == (comparison_object)
# Delegates to id in order to allow two records of the same type and id to work with something like:
# [ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]
def hash
# For checking respond_to? without searching the attributes (which is faster).
alias_method :respond_to_without_attributes?, :respond_to?
# 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.
def respond_to?(method)
self.class.column_methods_hash[method.to_sym] || respond_to_without_attributes?(method)
# Loads the <tt>file_name</tt> if reload_associations is true or requires if it's false.
def require_association(file_name)
if !associations_loaded.include?(file_name)
associations_loaded << file_name
reload_associations ? silence_warnings { load("#{file_name}.rb") } : require(file_name)
Object.send(:define_method, :require_association) { |file_name| ActiveRecord::Base.require_association(file_name) }
def create_or_update
if new_record? then create else update end
# Updates the associated record with values matching those of the instant attributes.
def update
"UPDATE #{self.class.table_name} " +
"SET #{quoted_comma_pair_list(connection, attributes_with_quotes(false))} " +
"WHERE #{self.class.primary_key} = '#{id}'",
"#{} Update"
# Creates a new record with values matching those of the instant attributes.
def create = connection.insert(
"INSERT INTO #{self.class.table_name} " +
"(#{quoted_column_names.join(', ')}) " +
"VALUES(#{attributes_with_quotes.values.join(', ')})",
"#{} Create",
@new_record = false
# Sets the attribute used for single table inheritance to this class name if this is not the ActiveRecord descendant.
# Considering the hierarchy Reply < Message < ActiveRecord, this makes it possible to do without having to
# set Reply[Reply.inheritance_column] = "Reply" yourself. No such attribute would be set for objects of the
# Message class in that example.
def ensure_proper_type
unless self.class.descends_from_active_record?
write_attribute(self.class.inheritance_column, Inflector.demodulize(
# 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, *arguments)
method_name = method_id.id2name
if method_name =~ read_method? && @attributes.include?($1)
return read_attribute($1)
elsif method_name =~ write_method? && @attributes.include?($1)
write_attribute($1, arguments[0])
elsif method_name =~ query_method? && @attributes.include?($1)
return query_attribute($1)
def read_method?() /^([a-zA-Z][-_\w]*)[^=?]*$/ end
def write_method?() /^([a-zA-Z][-_\w]*)=.*$/ end
def query_method?() /^([a-zA-Z][-_\w]*)\?$/ end
# Returns the value of attribute identified by <tt>attr_name</tt> after it has been type cast (for example,
# "2004-12-12" in a data column is cast to a date object, like, 12, 12)).
def read_attribute(attr_name) #:doc:
if @attributes.keys.include? attr_name
if column = column_for_attribute(attr_name)
@attributes[attr_name] = unserializable_attribute?(attr_name, column) ?
unserialize_attribute(attr_name) : column.type_cast(@attributes[attr_name])
# Returns true if the attribute is of a text column and marked for serialization.
def unserializable_attribute?(attr_name, column)
@attributes[attr_name] && column.send(:type) == :text && @attributes[attr_name].is_a?(String) && self.class.serialized_attributes[attr_name]
# 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])
@attributes[attr_name] = unserialized_object
"#{attr_name} was supposed to be a #{self.class.serialized_attributes[attr_name]}, " +
"but was a #{unserialized_object.class.to_s}"
# 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) #:doc:
@attributes[attr_name] = empty_string_for_number_column?(attr_name, value) ? nil : value
def empty_string_for_number_column?(attr_name, value)
column = column_for_attribute(attr_name)
column && (column.klass == Fixnum || column.klass == Float) && value == ""
def query_attribute(attr_name)
attribute = @attributes[attr_name]
if attribute.kind_of?(Fixnum) && attribute == 0
elsif attribute.kind_of?(String) && attribute == "0"
elsif attribute.kind_of?(String) && attribute.empty?
elsif attribute.nil?
elsif attribute == false
elsif attribute == "f"
elsif attribute == "false"
def remove_attributes_protected_from_mass_assignment(attributes)
if self.class.accessible_attributes.nil? && self.class.protected_attributes.nil?
attributes.reject { |key, value| key == self.class.primary_key }
elsif self.class.protected_attributes.nil?
attributes.reject { |key, value| !self.class.accessible_attributes.include?(key.intern) || key == self.class.primary_key }
elsif self.class.accessible_attributes.nil?
attributes.reject { |key, value| self.class.protected_attributes.include?(key.intern) || key == self.class.primary_key }
# Returns copy of the attributes hash where all the values have been safely quoted for use in
# an SQL statement.
def attributes_with_quotes(include_primary_key = true)
columns_hash = self.class.columns_hash
@attributes.inject({}) do |attrs_quoted, pair|
attrs_quoted[pair.first] = quote(pair.last, columns_hash[pair.first]) unless !include_primary_key && pair.first == self.class.primary_key
# Quote strings appropriately for SQL statements.
def quote(value, column = nil)
connection.quote(value, column)
# Interpolate custom sql string in instance context.
# Optional record argument is meant for custom insert_sql.
def interpolate_sql(sql, record = nil)
# Initializes the attributes array with keys matching the columns from the linked table and
# the values matching the corresponding default value of that column, so
# that a new instance, or one populated from a passed-in Hash, still has all the attributes
# that instances loaded from the database would.
def attributes_from_column_definition
connection.columns(self.class.table_name, "#{} Columns").inject({}) do |attributes, column|
attributes[] = column.default unless == self.class.primary_key
# Instantiates objects for all attribute classes that needs more than one constructor parameter. This is done
# by calling new on the column type or aggregation type (through composed_of) object with these parameters.
# So having the pairs written_on(1) = "2004", written_on(2) = "6", written_on(3) = "24", will instantiate
# written_on (a date type) with"2004", "6", "24"). You can also specify a typecast character in the
# parenteses to have the parameters typecasted before they're used in the constructor. Use i for Fixnum, f for Float,
# s for String, and a for Array. If all the values for a given attribute is empty, the attribute will be set to nil.
def assign_multiparameter_attributes(pairs)
# Includes an ugly hack for Time.local instead of because the latter is reserved by Time itself.
def execute_callstack_for_multiparameter_attributes(callstack)
callstack.each do |name, values|
klass = (self.class.reflect_on_aggregation(name) || column_for_attribute(name)).klass
if values.empty?
send(name + "=", nil)
send(name + "=", Time == klass ? klass.local(*values) :*values))
def extract_callstack_for_multiparameter_attributes(pairs)
attributes = { }
for pair in pairs
multiparameter_name, value = pair
attribute_name = multiparameter_name.split("(").first
attributes[attribute_name] = [] unless attributes.include?(attribute_name)
unless value.empty?
attributes[attribute_name] <<
[find_parameter_position(multiparameter_name), type_cast_attribute_value(multiparameter_name, value)]
attributes.each { |name, values| attributes[name] = values.sort_by{ |v| v.first }.collect { |v| v.last } }
def type_cast_attribute_value(multiparameter_name, value)
multiparameter_name =~ /\([0-9]*([a-z])\)/ ? value.send("to_" + $1) : value
def find_parameter_position(multiparameter_name)
# Returns a comma-separated pair list, like "key1 = val1, key2 = val2".
def comma_pair_list(hash)
hash.inject([]) { |list, pair| list << "#{pair.first} = #{pair.last}" }.join(", ")
def quoted_column_names(attributes = attributes_with_quotes)
attributes.keys.collect { |column_name| connection.quote_column_name(column_name) }
def quote_columns(column_quoter, hash)
hash.inject({}) {|list, pair|
list[column_quoter.quote_column_name(pair.first)] = pair.last
def quoted_comma_pair_list(column_quoter, hash)
comma_pair_list(quote_columns(column_quoter, hash))
def object_from_yaml(string)
return string unless String === string
if has_yaml_encoding_header?(string)
rescue Object
# Apparently wasn't YAML anyway
def has_yaml_encoding_header?(string)
string[0..3] == "--- "
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