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.
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 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 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])
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[:attribute]=(value) and self[:attribute] instead of write_attribute(:attribute, vaule) and read_attribute(:attribute) as a shorter form.
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 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
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
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 Company.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
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.
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.
VALID_FIND_OPTIONS | = | [ :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :from, :lock ] |
set_table_name | -> | table_name= |
set_primary_key | -> | primary_key= |
set_inheritance_column | -> | inheritance_column= |
set_sequence_name | -> | sequence_name= |
sanitize_sql | -> | sanitize_conditions |
respond_to? | -> | respond_to_without_attributes? |
For checking respond_to? without searching the attributes (which is faster). | ||
connection= | -> | connection_without_query_cache= |
abstract_class | [RW] | Set this to true if this is an abstract class (see abstract_class?). |
Overwrite the default class equality method to provide support for association proxies.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 948 948: def ===(object) 949: object.is_a?(self) 950: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 974 974: def abstract_class? 975: abstract_class == true 976: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 563 563: def attr_accessible(*attributes) 564: write_inheritable_array("attr_accessible", attributes - (accessible_attributes || [])) 565: end
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"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 550 550: def attr_protected(*attributes) 551: write_inheritable_array("attr_protected", attributes - (protected_attributes || [])) 552: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 965 965: def base_class 966: class_of_active_record_descendant(self) 967: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 843 843: def benchmark(title, log_level = Logger::DEBUG, use_silence = true) 844: if logger && logger.level == log_level 845: result = nil 846: seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield } 847: logger.add(log_level, "#{title} (#{'%.5f' % seconds})") 848: result 849: else 850: yield 851: end 852: end
Clears the cache which maps classes to connections.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 84 84: def clear_active_connections! 85: clear_cache!(@@active_connections) do |name, conn| 86: conn.disconnect! 87: end 88: end
Returns an array of column names as strings.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 771 771: def column_names 772: @column_names ||= columns.map { |column| column.name } 773: end
Returns an array of column objects for the table associated with this class.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 757 757: def columns 758: unless @columns 759: @columns = connection.columns(table_name, "#{name} Columns") 760: @columns.each {|column| column.primary = column.name == primary_key} 761: end 762: @columns 763: end
Returns an array of column objects for the table associated with this class.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 766 766: def columns_hash 767: @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash } 768: end
Returns true if a connection that’s accessible to this class have already been opened.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 229 229: def self.connected? 230: active_connections[active_connection_name] ? true : false 231: end
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.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 73 73: def connection 74: if @active_connection_name && (conn = active_connections[@active_connection_name]) 75: conn 76: else 77: # retrieve_connection sets the cache key. 78: conn = retrieve_connection 79: active_connections[@active_connection_name] = conn 80: end 81: end
# File vendor/rails/activerecord/lib/active_record/query_cache.rb, line 50 50: def connection=(spec) 51: if spec.is_a?(ConnectionSpecification) and spec.config[:query_cache] 52: spec = QueryCache.new(self.send(spec.adapter_method, spec.config)) 53: end 54: self.connection_without_query_cache = spec 55: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 777 777: def content_columns 778: @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column } 779: end
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"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 515 515: def count_by_sql(sql) 516: sql = sanitize_conditions(sql) 517: connection.select_value(sql, "#{name} Count").to_i 518: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 442 442: def create(attributes = nil) 443: if attributes.is_a?(Array) 444: attributes.collect { |attr| create(attr) } 445: else 446: object = new(attributes) 447: scope(:create).each { |att,value| object.send("#{att}=", value) } if scoped?(:create) 448: object.save 449: object 450: end 451: end
Works like increment_counter, but decrements instead.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 530 530: def decrement_counter(counter_name, id) 531: update_all "#{counter_name} = #{counter_name} - 1", "#{primary_key} = #{quote(id)}" 532: end
Deletes the record with the given id without instantiating an object first. If an array of ids is provided, all of them are deleted.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 478 478: def delete(id) 479: delete_all([ "#{primary_key} IN (?)", id ]) 480: end
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')"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 507 507: def delete_all(conditions = nil) 508: sql = "DELETE FROM #{table_name} " 509: add_conditions!(sql, conditions, scope(:find)) 510: connection.delete(sql, "#{name} Delete all") 511: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 484 484: def destroy(id) 485: id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy 486: end
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'"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 500 500: def destroy_all(conditions = nil) 501: find(:all, :conditions => conditions).each { |object| object.destroy } 502: end
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.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 181 181: def self.establish_connection(spec = nil) 182: case spec 183: when nil 184: raise AdapterNotSpecified unless defined? RAILS_ENV 185: establish_connection(RAILS_ENV) 186: when ConnectionSpecification 187: clear_active_connection_name 188: @active_connection_name = name 189: @@defined_connections[name] = spec 190: when Symbol, String 191: if configuration = configurations[spec.to_s] 192: establish_connection(configuration) 193: else 194: raise AdapterNotSpecified, "#{spec} database is not configured" 195: end 196: else 197: spec = spec.symbolize_keys 198: unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end 199: adapter_method = "#{spec[:adapter]}_connection" 200: unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end 201: remove_connection 202: establish_connection(ConnectionSpecification.new(spec, adapter_method)) 203: end 204: end
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}%"])
# File vendor/rails/activerecord/lib/active_record/base.rb, line 434 434: def exists?(id_or_conditions) 435: !find(:first, :conditions => expand_id_conditions(id_or_conditions)).nil? 436: rescue ActiveRecord::ActiveRecordError 437: false 438: end
Find operates with three different retrieval approaches:
All approaches accept an option hash as their last parameter. The options are:
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 408 408: def find(*args) 409: options = extract_options_from_args!(args) 410: validate_find_options(options) 411: set_readonly_option!(options) 412: 413: case args.first 414: when :first then find_initial(options) 415: when :all then find_every(options) 416: else find_from_ids(args, options) 417: end 418: end
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]
# File vendor/rails/activerecord/lib/active_record/base.rb, line 423 423: def find_by_sql(sql) 424: connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) } 425: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 525 525: def increment_counter(counter_name, id) 526: update_all "#{counter_name} = #{counter_name} + 1", "#{primary_key} = #{quote(id)}" 527: end
Defines the column name for use with single table inheritance — can be overridden in subclasses.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 652 652: def inheritance_column 653: "type" 654: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1478 1478: def initialize(attributes = nil) 1479: @attributes = attributes_from_column_definition 1480: @new_record = true 1481: ensure_proper_type 1482: self.attributes = attributes unless attributes.nil? 1483: yield self if block_given? 1484: end
Defines the primary key field — can be overridden in subclasses. Overwriting will negate any effect of the primary_key_prefix_type setting, though.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 635 635: def primary_key 636: reset_primary_key 637: end
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.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 237 237: def self.remove_connection(klass=self) 238: spec = @@defined_connections[klass.name] 239: konn = active_connections[klass.name] 240: @@defined_connections.delete_if { |key, value| value == spec } 241: active_connections.delete_if { |key, value| value == konn } 242: konn.disconnect! if konn 243: spec.config if spec 244: end
Resets all the cached information about columns, which will cause them to be reloaded on the next request.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 801 801: def reset_column_information 802: read_methods.each { |name| undef_method(name) } 803: @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @read_methods = nil 804: end
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 SerializationTypeMismatch will be raised.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 576 576: def serialize(attr_name, class_name = Object) 577: serialized_attributes[attr_name.to_s] = class_name 578: end
Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 581 581: def serialized_attributes 582: read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {}) 583: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 706 706: def set_inheritance_column(value = nil, &block) 707: define_attr_method :inheritance_column, value, &block 708: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 690 690: def set_primary_key(value = nil, &block) 691: define_attr_method :primary_key, value, &block 692: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 727 727: def set_sequence_name(value = nil, &block) 728: define_attr_method :sequence_name, value, &block 729: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 676 676: def set_table_name(value = nil, &block) 677: define_attr_method :table_name, value, &block 678: end
Silences the logger for the duration of the block.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 855 855: def silence 856: old_logger_level, logger.level = logger.level, Logger::ERROR if logger 857: yield 858: ensure 859: logger.level = old_logger_level if logger 860: end
Indicates whether the table associated with this class exists
# File vendor/rails/activerecord/lib/active_record/base.rb, line 741 741: def table_exists? 742: if connection.respond_to?(:tables) 743: connection.tables.include? table_name 744: else 745: # if the connection adapter hasn't implemented tables, there are two crude tests that can be 746: # used - see if getting column info raises an error, or if the number of columns returned is zero 747: begin 748: reset_column_information 749: columns.size > 0 750: rescue ActiveRecord::StatementInvalid 751: false 752: end 753: end 754: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 608 608: def table_name 609: reset_table_name 610: end
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)
# File vendor/rails/activerecord/lib/active_record/base.rb, line 465 465: def update(id, attributes) 466: if id.is_a?(Array) 467: idx = -1 468: id.collect { |id| idx += 1; update(id, attributes[idx]) } 469: else 470: object = find(id) 471: object.update_attributes(attributes) 472: object 473: end 474: end
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'"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 491 491: def update_all(updates, conditions = nil) 492: sql = "UPDATE #{table_name} SET #{sanitize_sql(updates)} " 493: add_conditions!(sql, conditions, scope(:find)) 494: connection.update(sql, "#{name} Update") 495: end
Works like with_scope, but discards any nested properties.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 943 943: def with_exclusive_scope(method_scoping = {}, &block) 944: with_scope(method_scoping, :overwrite, &block) 945: end
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
# File vendor/rails/activerecord/lib/active_record/base.rb, line 891 891: def with_scope(method_scoping = {}, action = :merge, &block) 892: method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping) 893: 894: # Dup first and second level of hash (method and params). 895: method_scoping = method_scoping.inject({}) do |hash, (method, params)| 896: hash[method] = (params == true) ? params : params.dup 897: hash 898: end 899: 900: method_scoping.assert_valid_keys([ :find, :create ]) 901: 902: if f = method_scoping[:find] 903: f.assert_valid_keys([ :conditions, :joins, :select, :include, :from, :offset, :limit, :order, :readonly, :lock ]) 904: f[:readonly] = true if !f[:joins].blank? && !f.has_key?(:readonly) 905: end 906: 907: # Merge scopings 908: if action == :merge && current_scoped_methods 909: method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)| 910: case hash[method] 911: when Hash 912: if method == :find 913: (hash[method].keys + params.keys).uniq.each do |key| 914: merge = hash[method][key] && params[key] # merge if both scopes have the same key 915: if key == :conditions && merge 916: hash[method][key] = [params[key], hash[method][key]].collect{ |sql| "( %s )" % sanitize_sql(sql) }.join(" AND ") 917: elsif key == :include && merge 918: hash[method][key] = merge_includes(hash[method][key], params[key]).uniq 919: else 920: hash[method][key] = hash[method][key] || params[key] 921: end 922: end 923: else 924: hash[method] = params.merge(hash[method]) 925: end 926: else 927: hash[method] = params 928: end 929: hash 930: end 931: end 932: 933: self.scoped_methods << method_scoping 934: 935: begin 936: yield 937: ensure 938: self.scoped_methods.pop 939: end 940: end
Returns the class descending directly from ActiveRecord in the inheritance hierarchy.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1357 1357: def class_of_active_record_descendant(klass) 1358: if klass.superclass == Base || klass.superclass.abstract_class? 1359: klass 1360: elsif klass.superclass.nil? 1361: raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord" 1362: else 1363: class_of_active_record_descendant(klass.superclass) 1364: end 1365: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1347 1347: def compute_type(type_name) 1348: modularized_name = type_name_with_module(type_name) 1349: begin 1350: instance_eval(modularized_name) 1351: rescue NameError => e 1352: instance_eval(type_name) 1353: end 1354: end
Accepts an array, hash, or string of sql conditions and deals with them accordingly
["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'"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1377 1377: def sanitize_sql(condition) 1378: return sanitize_sql_array(condition) if condition.is_a?(Array) 1379: return sanitize_sql_hash(condition) if condition.is_a?(Hash) 1380: condition 1381: end
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'"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1395 1395: def sanitize_sql_array(ary) 1396: statement, *values = ary 1397: if values.first.is_a?(Hash) and statement =~ /:\w+/ 1398: replace_named_bind_variables(statement, values.first) 1399: elsif statement.include?('?') 1400: replace_bind_variables(statement, values) 1401: else 1402: statement % values.collect { |value| connection.quote_string(value.to_s) } 1403: end 1404: end
Accepts a hash of conditions. The hash has each key/value or attribute/value pair sanitized and interpolated into the sql statement.
{ :name => "foo'bar", :group_id => 4 } returns "name='foo''bar' and group_id= 4"
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1386 1386: def sanitize_sql_hash(hash) 1387: hash.collect { |attrib, value| 1388: "#{table_name}.#{connection.quote_column_name(attrib)} = #{quote(value)}" 1389: }.join(" AND ") 1390: end
Returns true if the comparison_object is the same object, or is of the same type and has the same id.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1701 1701: def ==(comparison_object) 1702: comparison_object.equal?(self) || 1703: (comparison_object.instance_of?(self.class) && 1704: comparison_object.id == id && 1705: !comparison_object.new_record?) 1706: end
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).
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1623 1623: def [](attr_name) 1624: read_attribute(attr_name) 1625: end
Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1629 1629: def []=(attr_name, value) 1630: write_attribute(attr_name, value) 1631: end
Returns an array of names for the attributes available on this object sorted alphabetically.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1691 1691: def attribute_names 1692: @attributes.keys.sort 1693: end
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).
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1680 1680: def attribute_present?(attribute) 1681: value = read_attribute(attribute) 1682: !value.blank? or value == 0 1683: end
Returns a hash of all the attributes with their names as keys and clones of their objects as values.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1653 1653: def attributes(options = nil) 1654: attributes = clone_attributes :read_attribute 1655: 1656: if options.nil? 1657: attributes 1658: else 1659: if except = options[:except] 1660: except = Array(except).collect { |attribute| attribute.to_s } 1661: except.each { |attribute_name| attributes.delete(attribute_name) } 1662: attributes 1663: elsif only = options[:only] 1664: only = Array(only).collect { |attribute| attribute.to_s } 1665: attributes.delete_if { |key, value| !only.include?(key) } 1666: attributes 1667: else 1668: raise ArgumentError, "Options does not specify :except or :only (#{options.keys.inspect})" 1669: end 1670: end 1671: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1638 1638: def attributes=(new_attributes) 1639: return if new_attributes.nil? 1640: attributes = new_attributes.dup 1641: attributes.stringify_keys! 1642: 1643: multi_parameter_attributes = [] 1644: remove_attributes_protected_from_mass_assignment(attributes).each do |k, v| 1645: k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v) 1646: end 1647: 1648: assign_multiparameter_attributes(multi_parameter_attributes) 1649: end
Returns a hash of cloned attributes before typecasting and deserialization.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1674 1674: def attributes_before_type_cast 1675: clone_attributes :read_attribute_before_type_cast 1676: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1551 1551: def clone 1552: attrs = self.attributes_before_type_cast 1553: attrs.delete(self.class.primary_key) 1554: self.class.new do |record| 1555: record.send :instance_variable_set, '@attributes', attrs 1556: end 1557: end
Returns the column object for the named attribute.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1696 1696: def column_for_attribute(name) 1697: self.class.columns_hash[name.to_s] 1698: end
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.
# File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 150 150: def connection 151: self.class.connection 152: end
Initializes the attribute to zero if nil and subtracts one. Only makes sense for number-based attributes. Returns self.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1587 1587: def decrement(attribute) 1588: self[attribute] ||= 0 1589: self[attribute] -= 1 1590: self 1591: end
Decrements the attribute and saves the record.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1594 1594: def decrement!(attribute) 1595: decrement(attribute).update_attribute(attribute, self[attribute]) 1596: end
Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can’t be persisted).
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1534 1534: def destroy 1535: unless new_record? 1536: connection.delete "DELETE FROM \#{self.class.table_name}\nWHERE \#{self.class.primary_key} = \#{quoted_id}\n", "#{self.class.name} Destroy" 1537: end 1538: 1539: freeze 1540: end
Delegates to ==
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1709 1709: def eql?(comparison_object) 1710: self == (comparison_object) 1711: end
Just freeze the attributes hash, such that associations are still accessible even on destroyed records.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1741 1741: def freeze 1742: @attributes.freeze; self 1743: end
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1745 1745: def frozen? 1746: @attributes.frozen? 1747: end
Returns true if the given attribute is in the attributes hash
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1686 1686: def has_attribute?(attr_name) 1687: @attributes.has_key?(attr_name.to_s) 1688: end
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) ]
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1715 1715: def hash 1716: id.hash 1717: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1488 1488: def id 1489: attr_name = self.class.primary_key 1490: column = column_for_attribute(attr_name) 1491: define_read_method(:id, attr_name, column) if self.class.generate_read_methods 1492: read_attribute(attr_name) 1493: end
Sets the primary ID.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1510 1510: def id=(value) 1511: write_attribute(self.class.primary_key, value) 1512: end
Initializes the attribute to zero if nil and adds one. Only makes sense for number-based attributes. Returns self.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1575 1575: def increment(attribute) 1576: self[attribute] ||= 0 1577: self[attribute] += 1 1578: self 1579: end
Increments the attribute and saves the record.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1582 1582: def increment!(attribute) 1583: increment(attribute).update_attribute(attribute, self[attribute]) 1584: end
Returns true if this object hasn’t been saved yet — that is, a record for the object doesn’t exist yet.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1515 1515: def new_record? 1516: @new_record 1517: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1750 1750: def readonly? 1751: @readonly == true 1752: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1613 1613: def reload(options = nil) 1614: clear_aggregation_cache 1615: clear_association_cache 1616: @attributes.update(self.class.find(self.id, options).instance_variable_get('@attributes')) 1617: self 1618: end
A Person object with a name attribute can ask person.respond_to?("name"), person.respond_to?("name="), and person.respond_to?("name?") which will all return true.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1724 1724: def respond_to?(method, include_priv = false) 1725: if @attributes.nil? 1726: return super 1727: elsif attr_name = self.class.column_methods_hash[method.to_sym] 1728: return true if @attributes.include?(attr_name) || attr_name == self.class.primary_key 1729: return false if self.class.read_methods.include?(attr_name) 1730: elsif @attributes.include?(method_name = method.to_s) 1731: return true 1732: elsif md = self.class.match_attribute_method?(method.to_s) 1733: return true if @attributes.include?(md.pre_match) 1734: end 1735: # super must be called at the end of the method, because the inherited respond_to? 1736: # would return true for generated readers, even if the attribute wasn't present 1737: super 1738: end
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1521 1521: def save 1522: raise ReadOnlyRecord if readonly? 1523: create_or_update 1524: end
Attempts to save the record, but instead of just returning false if it couldn’t happen, it raises a RecordNotSaved exception
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1528 1528: def save! 1529: save || raise(RecordNotSaved) 1530: end
Enables Active Record objects to be used as URL parameters in Action Pack automatically.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1496 1496: def to_param 1497: # We can't use alias_method here, because method 'id' optimizes itself on the fly. 1498: (id = self.id) ? id.to_s : nil # Be sure to stringify the id for routes 1499: end
Turns an attribute that’s currently true into false and vice versa. Returns self.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1599 1599: def toggle(attribute) 1600: self[attribute] = !send("#{attribute}?") 1601: self 1602: end
Toggles the attribute and saves the record.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1605 1605: def toggle!(attribute) 1606: toggle(attribute).update_attribute(attribute, self[attribute]) 1607: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1562 1562: def update_attribute(name, value) 1563: send(name.to_s + '=', value) 1564: save 1565: end
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.
# File vendor/rails/activerecord/lib/active_record/base.rb, line 1569 1569: def update_attributes(attributes) 1570: self.attributes = attributes 1571: save 1572: end