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 link: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 an 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 an 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, :conditions => [
  "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 sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and 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, value) and read_attribute(:attribute) as a shorter form.

Attribute query methods

In addition to the basic accessors, query methods are also automatically available on the Active Record object. Query methods allow you to test whether an attribute value is present.

For example, an Active Record User with the name attribute has a name? method that you can call to determine whether the user has a name:

user = User.new(:name => "David")
user.name? # => true

anonymous = User.new(:name => "")
anonymous.name? # => false

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, :conditions => ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, :conditions => ["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, :conditions => ["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

To find by a subset of the attributes to be used for instantiating a new object, pass a hash instead of a list of parameters. For example:

Tag.find_or_create_by_name(:name => "rails", :creator => current_user)

That will either find an existing tag named "rails", or create a new one while setting the user that created it.

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 named "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/singleTableInherit...

Connection to multiple databases in different models

Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection. All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection. For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course.establish_connection and Course *and all its subclasses* will use this connection instead.

This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.

Exceptions

• ActiveRecordError — generic error class and superclass of all other errors raised by Active Record
• AdapterNotSpecified — the configuration hash used in establish_connection didn’t include an :adapter key.
• AdapterNotFound — the :adapter key used in establish_connection specified a 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 serialized object 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.</attribute>

Classes
ConnectionSpecification

Constants
VALID_FIND_OPTIONS

Aliases
inheritance_column=
primary_key=
sanitize_conditions
sanitize_sql
sanitize_sql_hash
sequence_name=
table_name=

Public Attributes
abstract_class	Set this to true if this is an abstract class (see #abstract_class?).

Public Methods
==	Returns true if the comparison_object is the same object, or is of the same type and has the same id.
===	Overwrite the default class equality method to provide support for association proxies.
[]	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).
[]=	Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).
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.
accessible_attributes	Returns an array of all the attributes that have been made accessible to mass-assignment.
active_connection_name
allow_concurrency=	set concurrency support flag (not thread safe, like most of the methods in this file)
attr_accessible	Similar to the attr_protected macro, this protects attributes of your model from mass-assignment, such as new(attributes) and attributes=(attributes) however, it does it in the opposite way. This locks all attributes and only allows access to the attributes specified. Assignment to attributes not in this list will be ignored and need to be set using the direct writer methods instead. This is meant to protect sensitive attributes from being overwritten by URL/form hackers. If you’d rather start from an all-open default and restrict attributes as needed, have a look at attr_protected.
attr_protected	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:
attr_readonly	Attributes listed as readonly can be set for a new record, but will be ignored in database updates afterwards.
attribute_for_inspect	Format attributes nicely for inspect.
attribute_names	Returns an array of names for the attributes available on this object sorted alphabetically.
attribute_present?	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).
attributes	Returns a hash of all the attributes with their names as keys and clones of their objects as values.
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 with the attr_accessible macro. Then all the attributes not included in that won’t be allowed to be mass-assigned.
attributes_before_type_cast	Returns a hash of cloned attributes before typecasting and deserialization.
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.
becomes	Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes(Company) to render that instance using the companies/company partial instead of clients/client.
benchmark	Log and benchmark multiple statements in a single block. Example:
cache_key	Returns a cache key that can be used to identify this record. Examples:
class_name	Turns the table_name back into a class name following the reverse rules of table_name.
clear_active_connection_name
clear_active_connections!	Clears the cache which maps classes to connections.
clear_reloadable_connections!	Clears the cache which maps classes
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.
column_for_attribute	Returns the column object for the named attribute.
column_methods_hash	Returns a hash of all the methods added to query each of the columns in the table with the name of the method as the key and true as the value. This makes it possible to do O(1) lookups in respond_to? to check if a given method for attribute is available.
column_names	Returns an array of column names as strings.
columns	Returns an array of column objects for the table associated with this class.
columns_hash	Returns a hash of column objects for the table associated with this class.
connected?	Returns true if a connection that’s accessible to this class has already been opened.
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.
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.
connection=	Set the connection for the class.
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.
count_by_sql	Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. The use of this method should be restricted to complicated SQL queries that can’t be executed using the ActiveRecord::Calculations class methods. Look into those before using this.
create	Creates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.
decrement	Initializes the attribute to zero if nil and subtracts the value passed as by (default is one). Only makes sense for number-based attributes. Returns self.
decrement!	Decrements the attribute and saves the record.
decrement_counter	Decrement a number field by one, usually representing a count.
delete	Delete an object (or multiple objects) where the id given matches the primary_key. A SQL DELETE command is executed on the database which means that no callbacks are fired off running this. This is an efficient method of deleting records that don’t need cleaning up after or other actions to be taken.
delete_all	Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method and invoking callbacks. This is a single SQL query, much more efficient than destroy_all.
descends_from_active_record?	True if this isn’t a concrete subclass needing a STI type condition.
destroy	Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.
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).
destroy_all	Destroys the records matching conditions by instantiating each record and calling the destroy method. This means at least 2*N database queries to destroy N records, so avoid destroy_all if you are deleting many records. If you want to simply delete records without worrying about dependent associations or callbacks, use the much faster delete_all method instead.
eql?	Delegates to ==
establish_connection	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):
exists?	Checks whether a record exists in the database that matches conditions given. These conditions can either be a single integer representing a primary key id to be found, or a condition to be matched like using ActiveRecord#find.
find	Find operates with three different retrieval approaches:
find_by_sql	Executes a custom sql query against your database and returns all the results. The results will be returned as an array with columns requested encapsulated as attributes of the model you call this method from. If you call +Product.find_by_sql+ then the results will be returned in a Product object with the attributes you specified in the SQL query.
finder_needs_type_condition?
freeze	Freeze the attributes hash such that associations are still accessible, even on destroyed records.
frozen?	Returns true if the attributes hash has been frozen.
has_attribute?	Returns true if the given attribute is in the attributes hash
hash	Delegates to id in order to allow two records of the same type and id to work with something like:
human_attribute_name	Transforms attribute key names into a more humane format, such as "First name" instead of "first_name". Example:
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.
id=	Sets the primary ID.
id_before_type_cast
increment	Initializes the attribute to zero if nil and adds the value passed as by (default is one). Only makes sense for number-based attributes. Returns self.
increment!	Increments the attribute and saves the record.
increment_counter	Increment a number field by one, usually representing a count.
inheritance_column	Defines the column name for use with single table inheritance — can be set in subclasses like so: self.inheritance_column = "type_id"
inherited
inspect	Returns a string like ‘Post id:integer, title:string, body:text’
inspect	Returns the contents of the record as a nicely formatted string.
log_connections	connection state logging
mysql_connection	Establishes a connection to the database that’s used by all Active Record objects.
new	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.
new_record?	Returns true if this object hasn’t been saved yet — that is, a record for the object doesn’t exist yet.
postgresql_connection	Establishes a connection to the database that’s used by all Active Record objects
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.
protected_attributes	Returns an array of all the attributes that have been protected from mass-assignment.
quote_value
quoted_id
readonly!	Marks this record as read only.
readonly?	Returns true if the record is read only. Records loaded through joins with piggy-back attributes will be marked as read only since they cannot be saved.
readonly_attributes	Returns an array of all the attributes that have been specified as readonly.
reload	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.
remove_connection	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 an argument for establish_connection, for easily re-establishing the connection.
require_mysql
reset_column_information	Resets all the cached information about columns, which will cause them to be reloaded on the next request.
reset_column_information_and_inheritable_attributes_for_all_subclasses
reset_primary_key
reset_sequence_name
reset_subclasses
reset_table_name
retrieve_connection	Locate the connection of the nearest super class. This can be an active or defined connection: if it is the latter, it will be opened and set as the active connection for the class it was defined for (not necessarily the current class).
sanitize	Used to sanitize objects before they’re used in an SQL SELECT statement. Delegates to connection.quote.
save
save!	Attempts to save the record, but instead of just returning false if it couldn’t happen, it raises a RecordNotSaved exception
sequence_name	Lazy-set the sequence name to the connection’s default. This method is only ever called once since set_sequence_name overrides it.
serialize	If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically. 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.
serialized_attributes	Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.
set_inheritance_column	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.
set_primary_key	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.
set_sequence_name	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.
set_table_name	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.
silence	Silences the logger for the duration of the block.
single_threaded_active_connections
sqlite3_connection	sqlite3 adapter reuses sqlite_connection.
sqlite_connection	Establishes a connection to the database that’s used by all Active Record objects
table_exists?	Indicates whether the table associated with this class exists
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 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. You can add new inflections in config/initializers/inflections.rb.
thread_safe_active_connections	Retrieve the connection cache.
to_param	Enables Active Record objects to be used as URL parameters in Action Pack automatically.
toggle	Turns an attribute that’s currently true into false and vice versa. Returns self.
toggle!	Toggles the attribute and saves the record.
update	Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.
update_all	Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied.
update_attribute	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 aren’t subjected to validation checks. Hence, attributes can be updated even if the full object isn’t valid.
update_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.
update_attributes!	Updates an object just like Base.update_attributes but calls save! instead of save so an exception is raised if the record is invalid.
update_counters	A generic "counter updater" implementation, intended primarily to be used by increment_counter and decrement_counter, but which may also be useful on its own. It simply does a direct SQL update for the record with the given ID, altering the given hash of counters by the amount given by the corresponding value:
verify_active_connections!	Verify active connections.

Protected Methods
aggregate_mapping
class_name_of_active_record_descendant	Returns the name of the class descending directly from ActiveRecord in the inheritance hierarchy.
class_of_active_record_descendant	Returns the class descending directly from ActiveRecord in the inheritance hierarchy.
compute_type	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.
current_scoped_methods
encode_quoted_value
expand_hash_conditions_for_aggregates	Accepts a hash of sql conditions and replaces those attributes that correspond to a composed_of relationship with their expanded aggregate attribute values. Given:
expand_range_bind_variables
quote_bound_value
raise_if_bind_arity_mismatch
replace_bind_variables
replace_named_bind_variables
sanitize_sql_array	Accepts an array of conditions. The array has each value sanitized and interpolated into the sql statement.
sanitize_sql_for_assignment	Accepts an array, hash, or string of sql conditions and sanitizes them into a valid SQL fragment for a SET clause.
sanitize_sql_for_conditions	Accepts an array, hash, or string of sql conditions and sanitizes them into a valid SQL fragment for a WHERE clause.
sanitize_sql_hash_for_assignment	Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.
sanitize_sql_hash_for_conditions	Sanitizes a hash of attribute/value pairs into SQL conditions for a WHERE clause.
scope	Retrieve the scope for the given method and optional key.
scoped?	Test whether the given method and optional key are scoped.
set_readonly_option!
single_threaded_scoped_methods
subclasses
thread_safe_scoped_methods
validate_find_options
with_exclusive_scope	Works like with_scope, but discards any nested properties.
with_scope	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.

Private Methods
add_conditions!	Adds a sanitized version of conditions to the sql string. Note that the passed-in sql string is changed. The optional scope argument is for the current :find scope.
add_group!
add_joins!	The optional scope argument is for the current :find scope.
add_limit!	The optional scope argument is for the current :find scope.
add_lock!	The optional scope argument is for the current :find scope. The :lock option has precedence over a scoped :lock.
add_order!
all_attributes_exists?
assign_multiparameter_attributes	Instantiates objects for all attribute classes that needs more than one constructor parameter. This is done by calling new on the column type or aggregation type (through composed_of) object with these parameters. So having the pairs written_on(1) = "2004", written_on(2) = "6", written_on(3) = "24", will instantiate written_on (a date type) with Date.new("2004", "6", "24"). You can also specify a typecast character in the parentheses to have the parameters typecasted before they’re used in the constructor. Use i for Fixnum, f for Float, s for String, and a for Array. If all the values for a given attribute are empty, the attribute will be set to nil.
attribute_condition
attributes_from_column_definition	Initializes the attributes array with keys matching the columns from the linked table and the values matching the corresponding default value of that column, so that a new instance, or one populated from a passed-in Hash, still has all the attributes that instances loaded from the database would.
attributes_protected_by_default	The primary key and inheritance column can never be set by mass-assignment for security reasons.
attributes_with_quotes	Returns a copy of the attributes hash where all the values have been safely quoted for use in an SQL statement.
clear_all_cached_connections!
clear_cache!
clone_attribute_value
clone_attributes
comma_pair_list	Returns a comma-separated pair list, like "key1 = val1, key2 = val2".
construct_attributes_from_arguments
construct_finder_sql
convert_number_column_value
create	Creates a record with values matching those of the instance attributes and returns its id.
create_or_update
define_attr_method	Defines an "attribute" method (like #inheritance_column or #table_name). A new (class) method will be created with the given name. If a value is specified, the new method will return that value (as a string). Otherwise, the given block will be used to compute the value of the method.
determine_finder
determine_instantiator
ensure_proper_type	Sets the attribute used for single table inheritance to this class name if this is not the ActiveRecord descendent. Considering the hierarchy Reply < Message < ActiveRecord, this makes it possible to do Reply.new without having to set Reply = "Reply" yourself. No such attribute would be set for objects of the Message class in that example.
execute_callstack_for_multiparameter_attributes
expand_attribute_names_for_aggregates	Similar in purpose to expand_hash_conditions_for_aggregates.
expand_id_conditions	Interpret Array and Hash as conditions and anything else as an id.
extract_attribute_names_from_match
extract_callstack_for_multiparameter_attributes
find_every
find_from_ids
find_initial
find_one
find_parameter_position
find_some
instantiate	Finder methods must instantiate through this method to work with the single-table inheritance model that makes it possible to create objects of different types from the same table.
instantiate_time_object	Includes an ugly hack for Time.local instead of Time.new because the latter is reserved by Time itself.
interpolate_sql	Interpolate custom sql string in instance context. Optional record argument is meant for custom insert_sql.
merge_includes	Merges includes so that the result is a valid include
method_missing	Enables dynamic finders like find_by_user_name(user_name) and find_by_user_name_and_password(user_name, password) that are turned into find(:first, :conditions => ["user_name = ?", user_name]) and find(:first, :conditions => ["user_name = ? AND password = ?", user_name, password]) respectively. Also works for find(:all) by using find_all_by_amount(50) that is turned into find(:all, :conditions => ["amount = ?", 50]).
object_from_yaml
parse_sqlite_config!
quote_columns
quote_value	Quote strings appropriately for SQL statements.
quoted_column_names
quoted_comma_pair_list
quoted_table_name
remove_attributes_protected_from_mass_assignment
remove_readonly_attributes	Removes attributes which have been marked as readonly.
remove_stale_cached_threads!	Remove stale threads from the cache.
safe_to_array	Object#to_a is deprecated, though it does have the desired behavior
type_cast_attribute_value
type_condition
type_name_with_module	Nest the type name in the same module as this class. Bar is "MyApp::Business::Bar" relative to MyApp::Business::Foo
undecorated_table_name	Guesses the table name, but does not decorate it with prefix and suffix information.
update	Updates the associated record with values matching those of the instance attributes. Returns the number of affected rows.