ActiveRecord::Base

Active Record objects don’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 files/README.html for more insight.

Creation

Active Records accept 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 = User.new(:name => "David", :occupation => "Code Artist")
user.name # => "David"

You can also use block initialization:

user = User.new do |u|
  u.name = "David"
  u.occupation = "Code Artist"
end

And of course you can just create a bare object and specify the attributes after the fact:

user = User.new
user.name = "David"
user.occupation = "Code Artist"

Conditions

Conditions can either be specified as a string, array, or hash 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 don’t involve tainted data. The hash form works much like the array form, except only equality and range is possible. Examples:

class User < ActiveRecord::Base
  def self.authenticate_unsafely(user_name, password)
    find(:first, :conditions => "user_name = '#{user_name}' AND password = '#{password}'")
  end

  def self.authenticate_safely(user_name, password)
    find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ])
  end

  def self.authenticate_safely_simply(user_name, password)
    find(:first, :conditions => { :user_name => user_name, :password => 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 and authenticate_safely_simply both 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).

When using multiple parameters in the conditions, it can easily become hard to read exactly what the fourth or fifth question mark is supposed to represent. In those cases, you can resort to named bind variables instead. That’s done by replacing the question marks with symbols and supplying a hash with values for the matching symbol keys:

Company.find(:first, [
  "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",
  { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }
])

Similarly, a simple hash without a statement will generate conditions based on equality with the SQL AND operator. For instance:

Student.find(:all, :conditions => { :first_name => "Harvey", :status => 1 })
Student.find(:all, :conditions => params[:student])

A range may be used in the hash to use the SQL BETWEEN operator:

Student.find(:all, :conditions => { :grade => 9..12 })

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

You can alternatively use self=(value) and self instead of write_attribute(:attribute, vaule) and read_attribute(:attribute) as a shorter form.

Accessing attributes before they have been typecasted

Sometimes you want to be able to read the raw attribute data without having the column-determined typecast run its course first. That can be done by using the <attribute>_before_type_cast accessors that all attributes have. For example, if your Account model has a balance attribute, you can call account.balance_before_type_cast or account.id_before_type_cast.

This is especially useful in validation situations where the user might supply a string for an integer field and you want to display the original string back in an error message. Accessing the attribute normally would typecast the string to 0, which isn’t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL. They work by appending the name of an attribute to find_by_ or find_all_by_, so you get finders like Person.find_by_user_name, Person.find_all_by_last_name, Payment.find_by_transaction_id. So instead of writing Person.find(:first, ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, ["last_name = ?", last_name]), you just do Person.find_all_by_last_name(last_name).

It’s also possible to use multiple attributes in the same find by separating them with “and”, so you get finders like Person.find_by_user_name_and_password or even Payment.find_by_purchaser_and_state_and_country. So instead of writing Person.find(:first, ["user_name = ? AND password = ?", user_name, password]), you just do Person.find_by_user_name_and_password(user_name, password).

It’s even possible to use all the additional parameters to find. For example, the full interface for Payment.find_all_by_amount is actually Payment.find_all_by_amount(amount, options). And the full interface to Person.find_by_user_name is actually Person.find_by_user_name(user_name, options). So you could call Payment.find_all_by_amount(50, :order => "created_on").

The same dynamic finder style can be used to create the object if it doesn’t already exist. This dynamic finder is called with find_or_create_by_ and will return the object if it already exists and otherwise creates it, then returns it. Example:

# No 'Summer' tag exists
Tag.find_or_create_by_name("Summer") # equal to Tag.create(:name => "Summer")

# Now the 'Summer' tag does exist
Tag.find_or_create_by_name("Summer") # equal to Tag.find_by_name("Summer")

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Example:

# No 'Winter' tag exists
winter = Tag.find_or_initialize_by_name("Winter")
winter.new_record? # true

Saving arrays, hashes, and other non-mappable 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-mappable objects without doing any additional work. Example:

class User < ActiveRecord::Base
  serialize :preferences
end

user = User.create(:preferences => { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }

You can also specify a class option as the second parameter 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, Hash
end

user = User.create(:preferences => %w( one two three ))
User.find(user.id).preferences    # 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 Base.inheritance_column). 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 will be saved in the companies table with type = “Firm”. You can then fetch this row again using ::find(:first, “name = ‘37signals’”) and it will return a Firm object.

If you don’t have a type column defined in your table, single-table inheritance won’t be triggered. In that case, it’ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

Note, all the attributes for all the cases are kept in the same table. Read more: www.martinfowler.com/eaaCatalog/singleTableInheritance.html

Connection to multiple databases in different models

Connections are usually created through ::establish_connection and retrieved by ::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 ::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 establish_connection didn't include a :adapter key.
AdapterNotFound -- the :adapter key used in establish_connection specified an non-existent 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 as the second parameter.
ConnectionNotEstablished -- no connection has been established. Use establish_connection 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.
MultiparameterAssignmentErrors -- collection of errors that occurred during a mass assignment using the attributes= method. The errors property of this exception contains an array of AttributeAssignmentError objects that should be inspected to determine which attributes triggered the errors.
AttributeAssignmentError -- an error occurred while doing a mass assignment through the attributes= method. You can inspect the attribute property of the exception object to determine which attribute triggered the error.

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.

Methods

#

==,
===,
[],
[]=

A

abstract_class?,
attr_accessible,
attr_protected,
attribute_names,
attribute_present?,
attributes,
attributes=,
attributes_before_type_cast

B

base_class,
benchmark

C

class_of_active_record_descendant,
clear_active_connections!,
clear_reloadable_connections!,
clone,
column_for_attribute,
column_names,
columns,
columns_hash,
compute_type,
connected?,
connection,
connection,
connection=,
connection_without_query_cache=,
content_columns,
count_by_sql,
create

D

decrement,
decrement!,
decrement_counter,
delete,
delete_all,
destroy,
destroy,
destroy_all

E

eql?,
establish_connection,
exists?

F

find,
find_by_sql,
freeze,
frozen?

H

has_attribute?,
hash

I

id,
id=,
increment,
increment!,
increment_counter,
inheritance_column,
inheritance_column=

N

new,
new_record?

P

primary_key,
primary_key=

R

readonly?,
reload,
remove_connection,
require_mysql,
reset_column_information,
respond_to?,
respond_to_without_attributes?

S

sanitize_conditions,
sanitize_sql,
sanitize_sql_array,
sanitize_sql_hash,
save,
save!,
sequence_name=,
serialize,
serialized_attributes,
set_inheritance_column,
set_primary_key,
set_sequence_name,
set_table_name,
silence

T

table_exists?,
table_name,
table_name=,
to_param,
toggle,
toggle!

U

update,
update_all,
update_attribute,
update_attributes,
update_attributes!

W

with_exclusive_scope,
with_scope

Constants

VALID_FIND_OPTIONS	=	[ :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :from, :lock ]

Attributes

[RW]	abstract_class	Set this to true if this is an abstract class (see abstract_class?).
[RW]	pluralize_table_names

Class Public methods

===(object)

Overwrite the default class equality method to provide support for association proxies.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 958
def ===(object)
  object.is_a?(self)
end

abstract_class?()

Returns whether this class is a base AR class. If A is a base class and B descends from A, then B.base_class will return B.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 984
def abstract_class?
  abstract_class == true
end

attr_accessible(*attributes)

If this macro is used, only those attributes named in it will be accessible for mass-assignment, such as new(attributes) and attributes=(attributes). 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.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 566
def attr_accessible(*attributes)
  write_inheritable_array("attr_accessible", attributes - (accessible_attributes || []))
end

attr_protected(*attributes)

Attributes named in this macro are protected from mass-assignment, such as new(attributes) and attributes=(attributes). Their assignment will simply be ignored. Instead, you can use the direct writer methods to do assignment. This is meant to protect sensitive attributes from being overwritten by URL/form hackers. Example:

class Customer < ActiveRecord::Base
  attr_protected :credit_rating
end

customer = Customer.new("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"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 553
def attr_protected(*attributes)
  write_inheritable_array("attr_protected", attributes - (protected_attributes || []))
end

base_class()

Returns the base AR subclass that this class descends from. If A extends AR::Base, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 975
def base_class
  class_of_active_record_descendant(self)
end

benchmark(title, log_level = Logger::DEBUG, use_silence = true)

Log and benchmark multiple statements in a single block. Example:

Project.benchmark("Creating project") do
  project = Project.create("name" => "stuff")
  project.create_manager("name" => "David")
  project.milestones << Milestone.find(:all)
end

The benchmark is only recorded if the current level of the logger matches the log_level, which makes it easy to include benchmarking statements in production software that will remain inexpensive because the benchmark will only be conducted if the log level is low enough.

The logging of the multiple statements is turned off unless use_silence is set to false.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 853
def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
  if logger && logger.level == log_level
    result = nil
    seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield }
    logger.add(log_level, "#{title} (#{'%.5f' % seconds})")
    result
  else
    yield
  end
end

clear_active_connections!()

Clears the cache which maps classes to connections.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 84
def clear_active_connections!
  clear_cache!(@@active_connections) do |name, conn|
    conn.disconnect!
  end
end

clear_reloadable_connections!()

Clears the cache which maps classes

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 91
def clear_reloadable_connections!
  @@active_connections.each do |name, conn|
    if conn.requires_reloading?
      conn.disconnect!
      @@active_connections.delete(name)
    end
  end
end

column_names()

Returns an array of column names as strings.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 775
def column_names
  @column_names ||= columns.map { |column| column.name }
end

columns()

Returns an array of column objects for the table associated with this class.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 761
def columns
  unless @columns
    @columns = connection.columns(table_name, "#{name} Columns")
    @columns.each {|column| column.primary = column.name == primary_key}
  end
  @columns
end

columns_hash()

Returns a hash of column objects for the table associated with this class.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 770
def columns_hash
  @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
end

connected?()

Returns true if a connection that’s accessible to this class have already been opened.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 239
def self.connected?
  active_connections[active_connection_name] ? true : false
end

connection()

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.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 73
def connection
  if @active_connection_name && (conn = active_connections[@active_connection_name])
    conn
  else
    # retrieve_connection sets the cache key.
    conn = retrieve_connection
    active_connections[@active_connection_name] = conn
  end
end

connection=(spec)

Also aliased as: connection_without_query_cache=

Source: show

# File rails/activerecord/lib/active_record/query_cache.rb, line 50
def connection=(spec)
  if spec.is_a?(ConnectionSpecification) and spec.config[:query_cache]
    spec = QueryCache.new(self.send(spec.adapter_method, spec.config))
  end
  self.connection_without_query_cache = spec
end

connection_without_query_cache=(spec)

content_columns()

Returns an array of column objects where the primary id, all columns ending in “_id” or “_count”, and columns used for single table inheritance have been removed.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 781
def content_columns
  @content_columns ||= columns.reject { |c| c.primary || c.name =~ %r(_id|_count)$/ || c.name == inheritance_column }
end

count_by_sql(sql)

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part.

Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 518
def count_by_sql(sql)
  sql = sanitize_conditions(sql)
  connection.select_value(sql, "#{name} Count").to_i
end

create(attributes = nil)

Creates an object, instantly saves it as a record (if the validation permits it), and returns it. If the save fails under validations, the unsaved object is still returned.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 445
def create(attributes = nil)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr) }
  else
    object = new(attributes)
    scope(:create).each { |att,value| object.send("#{att}=", value) } if scoped?(:create)
    object.save
    object
  end
end

decrement_counter(counter_name, id)

Works like ::increment_counter, but decrements instead.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 533
def decrement_counter(counter_name, id)
  update_all "#{connection.quote_column_name(counter_name)} = #{connection.quote_column_name(counter_name)} - 1", "#{connection.quote_column_name(primary_key)} = #{quote_value(id)}"
end

delete(id)

Deletes the record with the given id without instantiating an object first. If an array of ids is provided, all of them are deleted.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 481
def delete(id)
  delete_all([ "#{connection.quote_column_name(primary_key)} IN (?)", id ])
end

delete_all(conditions = nil)

Deletes all the records that match the condition without instantiating the objects first (and hence not calling the destroy method). Example:

Post.delete_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 510
def delete_all(conditions = nil)
  sql = "DELETE FROM #{table_name} "
  add_conditions!(sql, conditions, scope(:find))
  connection.delete(sql, "#{name} Delete all")
end

destroy(id)

Destroys the record with the given id by instantiating the object and calling destroy (all the callbacks are the triggered). If an array of ids is provided, all of them are destroyed.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 487
def destroy(id)
  id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy
end

destroy_all(conditions = nil)

Destroys the objects for all the records that match the condition by instantiating each object and calling the destroy method. Example:

Person.destroy_all "last_login < '2004-04-04'"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 503
def destroy_all(conditions = nil)
  find(:all, :conditions => conditions).each { |object| object.destroy }
end

establish_connection(spec = nil)

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, Postgresql, etc):

ActiveRecord::Base.establish_connection(
  :adapter  => "mysql",
  :host     => "localhost",
  :username => "myuser",
  :password => "mypass",
  :database => "somedatabase"
)

Example for SQLite database:

ActiveRecord::Base.establish_connection(
  :adapter => "sqlite",
  :database  => "path/to/dbfile"
)

Also accepts keys as strings (for parsing from yaml for example):

ActiveRecord::Base.establish_connection(
  "adapter" => "sqlite",
  "database"  => "path/to/dbfile"
)

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 191
def self.establish_connection(spec = nil)
  case spec
    when nil
      raise AdapterNotSpecified unless defined? RAILS_ENV
      establish_connection(RAILS_ENV)
    when ConnectionSpecification
      clear_active_connection_name
      @active_connection_name = name
      @@defined_connections[name] = spec
    when Symbol, String
      if configuration = configurations[spec.to_s]
        establish_connection(configuration)
      else
        raise AdapterNotSpecified, "#{spec} database is not configured"
      end
    else
      spec = spec.symbolize_keys
      unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
      adapter_method = "#{spec[:adapter]}_connection"
      unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
      remove_connection
      establish_connection(ConnectionSpecification.new(spec, adapter_method))
  end
end

exists?(id_or_conditions)

Returns true if the given id represents the primary key of a record in the database, false otherwise. You can also pass a set of SQL conditions. Example:

Person.exists?(5)
Person.exists?('5')
Person.exists?(:name => "David")
Person.exists?(['name LIKE ?', "%#{query}%"])

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 437
def exists?(id_or_conditions)
  !find(:first, :conditions => expand_id_conditions(id_or_conditions)).nil?
rescue ActiveRecord::ActiveRecordError
  false
end

find(*args)

Find operates with three different retrieval approaches:

Find by id: This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised.
Find first: This will return the first record matched by the options used. These options can either be specific conditions or merely an order. If no record can matched, nil is returned.
Find all: This will return all the records matched by the options used. If no records are found, an empty array is returned.

All approaches accept an option hash as their last parameter. The options are:

:conditions: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
:order: An SQL fragment like "created_at DESC, name".
:group: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
:limit: An integer determining the limit on the number of rows that should be returned.
:offset: An integer determining the offset from where the rows should be fetched. So at 5, it would skip the first 4 rows.
:joins: An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed). The records will be returned read-only since they will have attributes that do not correspond to the table's columns. Pass :readonly => false to override.
:include: Names associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer to already defined associations. See eager loading under Associations.
:select: By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not include the joined columns.
:from: By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
:readonly: Mark the returned records read-only so they cannot be saved or updated.
:lock: An SQL fragment like "FOR UPDATE" or "LOCK IN SHARE MODE". :lock => true gives connection's default exclusive lock, usually "FOR UPDATE".

Examples for find by id:

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)
Person.find([1])     # returns an array for objects the object with ID = 1
Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

Examples for find first:

Person.find(:first) # returns the first object fetched by SELECT * FROM people
Person.find(:first, :conditions => [ "user_name = ?", user_name])
Person.find(:first, :order => "created_on DESC", :offset => 5)

Examples for find all:

Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people
Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50)
Person.find(:all, :offset => 10, :limit => 10)
Person.find(:all, :include => [ :account, :friends ])
Person.find(:all, :group => "category")

Example for find with a lock. Imagine two concurrent transactions: each will read person.visits == 2, add 1 to it, and save, resulting in two saves of person.visits = 3. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4.

Person.transaction do
  person = Person.find(1, :lock => true)
  person.visits += 1
  person.save!
end

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 411
def find(*args)
  options = extract_options_from_args!(args)
  validate_find_options(options)
  set_readonly_option!(options)

  case args.first
    when :first then find_initial(options)
    when :all   then find_every(options)
    else             find_from_ids(args, options)
  end
end

find_by_sql(sql)

Works like find(:all), but requires a complete SQL string. Examples:

Post.find_by_sql "SELECT p.*, c.author FROM posts p, comments c WHERE p.id = c.post_id"
Post.find_by_sql ["SELECT * FROM posts WHERE author = ? AND created > ?", author_id, start_date]

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 426
def find_by_sql(sql)
  connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
end

increment_counter(counter_name, id)

Increments the specified counter by one. So DiscussionBoard.increment_counter("post_count", discussion_board_id) would increment the “post_count” counter on the board responding to discussion_board_id. This is used for caching aggregate values, so that they don’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.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 528
def increment_counter(counter_name, id)
  update_all "#{connection.quote_column_name(counter_name)} = #{connection.quote_column_name(counter_name)} + 1", "#{connection.quote_column_name(primary_key)} = #{quote_value(id)}"
end

inheritance_column()

Defines the column name for use with single table inheritance – can be set in subclasses like so: self.inheritance_column = “type_id”

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 656
def inheritance_column
  @inheritance_column ||= "type".freeze
end

inheritance_column=(value = nil, &block)

new(attributes = nil)

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.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1504
def initialize(attributes = nil)
  @attributes = attributes_from_column_definition
  @new_record = true
  ensure_proper_type
  self.attributes = attributes unless attributes.nil?
  yield self if block_given?
end

primary_key()

Defines the primary key field – can be overridden in subclasses. Overwriting will negate any effect of the primary_key_prefix_type setting, though.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 638
def primary_key
  reset_primary_key
end

primary_key=(value = nil, &block)

remove_connection(klass=self)

Remove the connection for this class. This will close the active connection and the defined connection (if they exist). The result can be used as argument for ::establish_connection, for easy re-establishing of the connection.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 247
def self.remove_connection(klass=self)
  spec = @@defined_connections[klass.name]
  konn = active_connections[klass.name]
  @@defined_connections.delete_if { |key, value| value == spec }
  active_connections.delete_if { |key, value| value == konn }
  konn.disconnect! if konn
  spec.config if spec
end

require_mysql()

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb, line 44
def self.require_mysql
  # Include the MySQL driver if one hasn't already been loaded
  unless defined? Mysql
    begin
      require_library_or_gem 'mysql'
    rescue LoadError => cannot_require_mysql
      # Use the bundled Ruby/MySQL driver if no driver is already in place
      begin
        require 'active_record/vendor/mysql'
      rescue LoadError
        raise cannot_require_mysql
      end
    end
  end

  # Define Mysql::Result.all_hashes
  MysqlCompat.define_all_hashes_method!
end

reset_column_information()

Resets all the cached information about columns, which will cause them to be reloaded on the next request.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 805
def reset_column_information
  read_methods.each { |name| undef_method(name) }
  @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @read_methods = @inheritance_column = nil
end

sequence_name=(value = nil, &block)

serialize(attr_name, class_name = Object)

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 retrieval, or nil. Otherwise, SerializationTypeMismatch will be raised.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 579
def serialize(attr_name, class_name = Object)
  serialized_attributes[attr_name.to_s] = class_name
end

serialized_attributes()

Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 584
def serialized_attributes
  read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
end

set_inheritance_column(value = nil, &block)

Sets the name of the inheritance column to use to the given value, or (if the value # is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_inheritance_column do
    original_inheritance_column + "_id"
  end
end

Also aliased as: inheritance_column=

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 710
def set_inheritance_column(value = nil, &block)
  define_attr_method :inheritance_column, value, &block
end

set_primary_key(value = nil, &block)

Sets the name of the primary key column to use to the given value, or (if the value is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_primary_key "sysid"
end

Also aliased as: primary_key=

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 694
def set_primary_key(value = nil, &block)
  define_attr_method :primary_key, value, &block
end

set_sequence_name(value = nil, &block)

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle or Firebird, it will default to the commonly used pattern of: #{::table_name}_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

Example:

class Project < ActiveRecord::Base
  set_sequence_name "projectseq"   # default would have been "project_seq"
end

Also aliased as: sequence_name=

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 731
def set_sequence_name(value = nil, &block)
  define_attr_method :sequence_name, value, &block
end

set_table_name(value = nil, &block)

Sets the table name to use to the given value, or (if the value is nil or false) to the value returned by the given block.

Example:

class Project < ActiveRecord::Base
  set_table_name "project"
end

Also aliased as: table_name=

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 680
def set_table_name(value = nil, &block)
  define_attr_method :table_name, value, &block
end

silence()

Silences the logger for the duration of the block.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 865
def silence
  old_logger_level, logger.level = logger.level, Logger::ERROR if logger
  yield
ensure
  logger.level = old_logger_level if logger
end

table_exists?()

Indicates whether the table associated with this class exists

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 745
def table_exists?
  if connection.respond_to?(:tables)
    connection.tables.include? table_name
  else
    # if the connection adapter hasn't implemented tables, there are two crude tests that can be
    # used - see if getting column info raises an error, or if the number of columns returned is zero
    begin
      reset_column_information
      columns.size > 0
    rescue ActiveRecord::StatementInvalid
      false
    end          
  end
end

table_name()

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 rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections (report a bug if your inflection isn’t covered).

Nested classes are given table names prefixed by the singular form of the parent's table name. Example:

file                  class               table_name
invoice.rb            Invoice             invoices
invoice/lineitem.rb   Invoice::Lineitem   invoice_lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have “myapp_” as a prefix, the table name guess for an Invoice class becomes “myapp_invoices”. Invoice::Lineitem becomes “myapp_invoice_lineitems”.

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
  set_table_name "mice"
end

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 611
def table_name
  reset_table_name
end

table_name=(value = nil, &block)

update(id, 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 fails under validations, the unsaved object is still returned.

The arguments may also be given as arrays in which case the update method is called for each pair of id and attributes and an array of objects is returned.

Example of updating one record:

Person.update(15, {:user_name => 'Samuel', :group => 'expert'})

Example of updating multiple records:

people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy"} }       
Person.update(people.keys, people.values)

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 468
def update(id, attributes)
  if id.is_a?(Array)
    idx = -1
    id.collect { |id| idx += 1; update(id, attributes[idx]) }
  else
    object = find(id)
    object.update_attributes(attributes)
    object
  end
end

update_all(updates, conditions = nil)

Updates all records with the SET-part of an SQL update statement in updates and returns an integer with the number of rows updated. A subset of the records can be selected by specifying conditions. Example:

Billing.update_all "category = 'authorized', approved = 1", "author = 'David'"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 494
def update_all(updates, conditions = nil)
  sql  = "UPDATE #{table_name} SET #{sanitize_sql(updates)} "
  add_conditions!(sql, conditions, scope(:find))
  connection.update(sql, "#{name} Update")
end

with_exclusive_scope(method_scoping = {}, &block)

Works like ::with_scope, but discards any nested properties.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 953
def with_exclusive_scope(method_scoping = {}, &block)
  with_scope(method_scoping, :overwrite, &block)
end

with_scope(method_scoping = {}, action = :merge, &block)

Scope parameters to method calls within the block. Takes a hash of method_name => parameters hash. method_name may be :find or :create. :find parameters may include the :conditions, :joins, :include, :offset, :limit, and :readonly options. :create parameters are an attributes hash.

Article.with_scope(:find => { :conditions => "blog_id = 1" }, :create => { :blog_id => 1 }) do
  Article.find(1) # => SELECT * from articles WHERE blog_id = 1 AND id = 1
  a = Article.create(1)
  a.blog_id # => 1
end

In nested scopings, all previous parameters are overwritten by inner rule except :conditions in :find, that are merged as hash.

Article.with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }, :create => { :blog_id => 1 }) do
  Article.with_scope(:find => { :limit => 10})
    Article.find(:all) # => SELECT * from articles WHERE blog_id = 1 LIMIT 10
  end
  Article.with_scope(:find => { :conditions => "author_id = 3" })
    Article.find(:all) # => SELECT * from articles WHERE blog_id = 1 AND author_id = 3 LIMIT 1
  end
end

You can ignore any previous scopings by using with_exclusive_scope method.

Article.with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }) do
  Article.with_exclusive_scope(:find => { :limit => 10 })
    Article.find(:all) # => SELECT * from articles LIMIT 10
  end
end

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 901
def with_scope(method_scoping = {}, action = :merge, &block)
  method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)

  # Dup first and second level of hash (method and params).
  method_scoping = method_scoping.inject({}) do |hash, (method, params)|
    hash[method] = (params == true) ? params : params.dup
    hash
  end

  method_scoping.assert_valid_keys([ :find, :create ])

  if f = method_scoping[:find]
    f.assert_valid_keys([ :conditions, :joins, :select, :include, :from, :offset, :limit, :order, :readonly, :lock ])
    f[:readonly] = true if !f[:joins].blank? && !f.has_key?(:readonly)
  end

  # Merge scopings
  if action == :merge && current_scoped_methods
    method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)|
      case hash[method]
        when Hash
          if method == :find
            (hash[method].keys + params.keys).uniq.each do |key|
              merge = hash[method][key] && params[key] # merge if both scopes have the same key
              if key == :conditions && merge
                hash[method][key] = [params[key], hash[method][key]].collect{ |sql| "( %s )" % sanitize_sql(sql) }.join(" AND ")
              elsif key == :include && merge
                hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
              else
                hash[method][key] = hash[method][key] || params[key]
              end
            end
          else
            hash[method] = params.merge(hash[method])
          end
        else
          hash[method] = params
      end
      hash
    end
  end

  self.scoped_methods << method_scoping

  begin
    yield
  ensure
    self.scoped_methods.pop
  end
end

Class Protected methods

class_of_active_record_descendant(klass)

Returns the class descending directly from ActiveRecord in the inheritance hierarchy.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1368
def class_of_active_record_descendant(klass)
  if klass.superclass == Base || klass.superclass.abstract_class?
    klass
  elsif klass.superclass.nil?
    raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
  else
    class_of_active_record_descendant(klass.superclass)
  end
end

compute_type(type_name)

Returns the class type of the record using the current module as a prefix. So descendents of MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1358
def compute_type(type_name)
  modularized_name = type_name_with_module(type_name)
  begin
    class_eval(modularized_name, __FILE__, __LINE__)
  rescue NameError
    class_eval(type_name, __FILE__, __LINE__)
  end
end

sanitize_conditions(condition)

sanitize_sql(condition)

Accepts an array, hash, or string of sql conditions and sanitizes them into a valid SQL fragment.

["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
{ :name => "foo'bar", :group_id => 4 }  returns "name='foo''bar' and group_id='4'"
"name='foo''bar' and group_id='4'" returns "name='foo''bar' and group_id='4'"

Also aliased as: sanitize_conditions

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1388
def sanitize_sql(condition)
  case condition
    when Array; sanitize_sql_array(condition)
    when Hash;  sanitize_sql_hash(condition)
    else        condition
  end
end

sanitize_sql_array(ary)

Accepts an array of conditions. The array has each value sanitized and interpolated into the sql statement.

["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1414
def sanitize_sql_array(ary)
  statement, *values = ary
  if values.first.is_a?(Hash) and statement =~ %r:\w+/
    replace_named_bind_variables(statement, values.first)
  elsif statement.include?('?')
    replace_bind_variables(statement, values)
  else
    statement % values.collect { |value| connection.quote_string(value.to_s) }
  end
end

sanitize_sql_hash(attrs)

Sanitizes a hash of attribute/value pairs into SQL conditions.

{ :name => "foo'bar", :group_id => 4 }
  # => "name='foo''bar' and group_id= 4"
{ :status => nil, :group_id => [1,2,3] }
  # => "status IS NULL and group_id IN (1,2,3)"
{ :age => 13..18 }
  # => "age BETWEEN 13 AND 18"

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1403
def sanitize_sql_hash(attrs)
  conditions = attrs.map do |attr, value|
    "#{table_name}.#{connection.quote_column_name(attr)} #{attribute_condition(value)}"
  end.join(' AND ')

  replace_bind_variables(conditions, expand_range_bind_variables(attrs.values))
end

Instance Public methods

==(comparison_object)

Returns true if the comparison_object is the same object, or is of the same type and has the same id.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1731
def ==(comparison_object)
  comparison_object.equal?(self) ||
    (comparison_object.instance_of?(self.class) && 
      comparison_object.id == id && 
      !comparison_object.new_record?)
end

[](attr_name)

Returns the value of the attribute identified by attr_name 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)). (Alias for the protected read_attribute method).

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1653
def [](attr_name)
  read_attribute(attr_name)
end

[]=(attr_name, value)

Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1659
def []=(attr_name, value)
  write_attribute(attr_name, value)
end

attribute_names()

Returns an array of names for the attributes available on this object sorted alphabetically.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1721
def attribute_names
  @attributes.keys.sort
end

attribute_present?(attribute)

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 respond to empty?, most notably Strings).

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1710
def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.blank? or value == 0
end

attributes(options = nil)

Returns a hash of all the attributes with their names as keys and clones of their objects as values.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1683
def attributes(options = nil)
  attributes = clone_attributes :read_attribute
  
  if options.nil?
    attributes
  else
    if except = options[:except]
      except = Array(except).collect { |attribute| attribute.to_s }
      except.each { |attribute_name| attributes.delete(attribute_name) }
      attributes
    elsif only = options[:only]
      only = Array(only).collect { |attribute| attribute.to_s }
      attributes.delete_if { |key, value| !only.include?(key) }
      attributes
    else
      raise ArgumentError, "Options does not specify :except or :only (#{options.keys.inspect})"
    end
  end
end

attributes=(new_attributes)

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.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1668
def attributes=(new_attributes)
  return if new_attributes.nil?
  attributes = new_attributes.dup
  attributes.stringify_keys!

  multi_parameter_attributes = []
  remove_attributes_protected_from_mass_assignment(attributes).each do |k, v|
    k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
  end

  assign_multiparameter_attributes(multi_parameter_attributes)
end

attributes_before_type_cast()

Returns a hash of cloned attributes before typecasting and deserialization.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1704
def attributes_before_type_cast
  clone_attributes :read_attribute_before_type_cast
end

clone()

Returns a clone of the record that hasn’t been assigned an id yet and is treated as a new record. Note that this is a “shallow” clone: it copies the object’s attributes only, not its associations. The extent of a “deep” clone is application-specific and is therefore left to the application to implement according to its need.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1575
def clone
  attrs = self.attributes_before_type_cast
  attrs.delete(self.class.primary_key)
  self.class.new do |record|
    record.send :instance_variable_set, '@attributes', attrs
  end
end

column_for_attribute(name)

Returns the column object for the named attribute.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1726
def column_for_attribute(name)
  self.class.columns_hash[name.to_s]
end

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.

Source: show

# File rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 160
def connection
  self.class.connection
end

decrement(attribute)

Initializes the attribute to zero if nil and subtracts one. Only makes sense for number-based attributes. Returns self.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1617
def decrement(attribute)
  self[attribute] ||= 0
  self[attribute] -= 1
  self
end

decrement!(attribute)

Decrements the attribute and saves the record.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1624
def decrement!(attribute)
  decrement(attribute).update_attribute(attribute, self[attribute])
end

destroy()

Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can’t be persisted).

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1559
      def destroy
        unless new_record?
          connection.delete "            DELETE FROM #{self.class.table_name}
            WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quoted_id}
", "#{self.class.name} Destroy"
        end

        freeze
      end

eql?(comparison_object)

Delegates to ==

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1739
def eql?(comparison_object)
  self == (comparison_object)
end

freeze()

Just freeze the attributes hash, such that associations are still accessible even on destroyed records.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1771
def freeze
  @attributes.freeze; self
end

frozen?()

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1775
def frozen?
  @attributes.frozen?
end

has_attribute?(attr_name)

Returns true if the given attribute is in the attributes hash

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1716
def has_attribute?(attr_name)
  @attributes.has_key?(attr_name.to_s)
end

hash()

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) ]

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1745
def hash
  id.hash
end

id()

A model instance's primary key is always available as model.id whether you name it the default 'id' or set it to something else.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1514
def id
  attr_name = self.class.primary_key
  column = column_for_attribute(attr_name)
  define_read_method(:id, attr_name, column) if self.class.generate_read_methods
  read_attribute(attr_name)
end

id=(value)

Sets the primary ID.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1536
def id=(value)
  write_attribute(self.class.primary_key, value)
end

increment(attribute)

Initializes the attribute to zero if nil and adds one. Only makes sense for number-based attributes. Returns self.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1605
def increment(attribute)
  self[attribute] ||= 0
  self[attribute] += 1
  self
end

increment!(attribute)

Increments the attribute and saves the record.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1612
def increment!(attribute)
  increment(attribute).update_attribute(attribute, self[attribute])
end

new_record?()

Returns true if this object hasn’t been saved yet – that is, a record for the object doesn’t exist yet.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1541
def new_record?
  @new_record
end

readonly?()

Records loaded through joins with piggy-back attributes will be marked as read only as they cannot be saved and return true to this query.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1780
def readonly?
  @readonly == true
end

reload(options = nil)

Reloads the attributes of this object from the database. The optional options argument is passed to find when reloading so you may do e.g. record.reload(:lock => true) to reload the same record with an exclusive row lock.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1643
def reload(options = nil)
  clear_aggregation_cache
  clear_association_cache
  @attributes.update(self.class.find(self.id, options).instance_variable_get('@attributes'))
  self
end

respond_to?(method, include_priv = false)

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.

Also aliased as: respond_to_without_attributes?

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1754
def respond_to?(method, include_priv = false)
  if @attributes.nil?
    return super
  elsif attr_name = self.class.column_methods_hash[method.to_sym]
    return true if @attributes.include?(attr_name) || attr_name == self.class.primary_key
    return false if self.class.read_methods.include?(attr_name)
  elsif @attributes.include?(method_name = method.to_s)
    return true
  elsif md = self.class.match_attribute_method?(method.to_s)
    return true if @attributes.include?(md.pre_match)
  end
  # super must be called at the end of the method, because the inherited respond_to?
  # would return true for generated readers, even if the attribute wasn't present
  super
end

respond_to_without_attributes?(method, include_priv = false)

For checking respond_to? without searching the attributes (which is faster).

save()

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.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1547
def save
  create_or_update
end

save!()

Attempts to save the record, but instead of just returning false if it couldn’t happen, it raises a RecordNotSaved exception

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1553
def save!
  create_or_update || raise(RecordNotSaved)
end

to_param()

Enables Active Record objects to be used as URL parameters in Action Pack automatically.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1522
def to_param
  # We can't use alias_method here, because method 'id' optimizes itself on the fly.
  (id = self.id) ? id.to_s : nil # Be sure to stringify the id for routes
end

toggle(attribute)

Turns an attribute that’s currently true into false and vice versa. Returns self.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1629
def toggle(attribute)
  self[attribute] = !send("#{attribute}?")
  self
end

toggle!(attribute)

Toggles the attribute and saves the record.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1635
def toggle!(attribute)
  toggle(attribute).update_attribute(attribute, self[attribute])
end

update_attribute(name, value)

Updates a single attribute and saves the record. This is especially useful for boolean flags on existing records. Note: This method is overwritten by the Validation module that’ll make sure that updates made with this method doesn’t get subjected to validation checks. Hence, attributes can be updated even if the full object isn’t valid.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1586
def update_attribute(name, value)
  send(name.to_s + '=', value)
  save
end

update_attributes(attributes)

Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1593
def update_attributes(attributes)
  self.attributes = attributes
  save
end

update_attributes!(attributes)

Updates an object just like #update_attributes but calls save! instead of save so an exception is raised if the record is invalid.

Source: show

# File rails/activerecord/lib/active_record/base.rb, line 1599
def update_attributes!(attributes)
  self.attributes = attributes
  save!
end

Class ActiveRecord::Base < Object

Creation

Conditions

Overwriting default accessors

Accessing attributes before they have been typecasted

Dynamic attribute-based finders

Saving arrays, hashes, and other non-mappable objects in text columns

Single table inheritance

Connection to multiple databases in different models

Exceptions