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module ActiveRecord
# = Active Record Persistence
module Persistence
extend ActiveSupport::Concern
module ClassMethods
# 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.
#
# The +attributes+ parameter can be either a Hash or an Array of Hashes. These Hashes describe the
# attributes on the objects that are to be created.
#
# ==== Examples
# # Create a single new object
# User.create(first_name: 'Jamie')
#
# # Create an Array of new objects
# User.create([{ first_name: 'Jamie' }, { first_name: 'Jeremy' }])
#
# # Create a single object and pass it into a block to set other attributes.
# User.create(first_name: 'Jamie') do |u|
# u.is_admin = false
# end
#
# # Creating an Array of new objects using a block, where the block is executed for each object:
# User.create([{ first_name: 'Jamie' }, { first_name: 'Jeremy' }]) do |u|
# u.is_admin = false
# end
def create(attributes = nil, &block)
if attributes.is_a?(Array)
attributes.collect { |attr| create(attr, &block) }
else
object = new(attributes, &block)
object.save
object
end
end
# Given an attributes hash, +instantiate+ returns a new instance of
# the appropriate class.
#
# For example, +Post.all+ may return Comments, Messages, and Emails
# by storing the record's subclass in a +type+ attribute. By calling
# +instantiate+ instead of +new+, finder methods ensure they get new
# instances of the appropriate class for each record.
#
# See +ActiveRecord::Inheritance#discriminate_class_for_record+ to see
# how this "single-table" inheritance mapping is implemented.
def instantiate(record, column_types = {})
klass = discriminate_class_for_record(record)
column_types = klass.decorate_columns(column_types.dup)
klass.allocate.init_with('attributes' => record, 'column_types' => column_types)
end
private
# Called by +instantiate+ to decide which class to use for a new
# record instance.
#
# See +ActiveRecord::Inheritance#discriminate_class_for_record+ for
# the single-table inheritance discriminator.
def discriminate_class_for_record(record)
self
end
end
# Returns true if this object hasn't been saved yet -- that is, a record
# for the object doesn't exist in the data store yet; otherwise, returns false.
def new_record?
sync_with_transaction_state
@new_record
end
# Returns true if this object has been destroyed, otherwise returns false.
def destroyed?
sync_with_transaction_state
@destroyed
end
# Returns true if the record is persisted, i.e. it's not a new record and it was
# not destroyed, otherwise returns false.
def persisted?
!(new_record? || destroyed?)
end
# Saves the model.
#
# If the model is new a record gets created in the database, otherwise
# the existing record gets updated.
#
# By default, save always run validations. If any of them fail the action
# is cancelled and +save+ returns +false+. However, if you supply
# validate: false, validations are bypassed altogether. See
# ActiveRecord::Validations for more information.
#
# There's a series of callbacks associated with +save+. If any of the
# <tt>before_*</tt> callbacks return +false+ the action is cancelled and
# +save+ returns +false+. See ActiveRecord::Callbacks for further
# details.
#
# Attributes marked as readonly are silently ignored if the record is
# being updated.
def save(*)
create_or_update
rescue ActiveRecord::RecordInvalid
false
end
# Saves the model.
#
# If the model is new a record gets created in the database, otherwise
# the existing record gets updated.
#
# With <tt>save!</tt> validations always run. If any of them fail
# ActiveRecord::RecordInvalid gets raised. See ActiveRecord::Validations
# for more information.
#
# There's a series of callbacks associated with <tt>save!</tt>. If any of
# the <tt>before_*</tt> callbacks return +false+ the action is cancelled
# and <tt>save!</tt> raises ActiveRecord::RecordNotSaved. See
# ActiveRecord::Callbacks for further details.
#
# Attributes marked as readonly are silently ignored if the record is
# being updated.
def save!(*)
create_or_update || raise(RecordNotSaved)
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). Returns the frozen instance.
#
# The row is simply removed with an SQL +DELETE+ statement on the
# record's primary key, and no callbacks are executed.
#
# To enforce the object's +before_destroy+ and +after_destroy+
# callbacks or any <tt>:dependent</tt> association
# options, use <tt>#destroy</tt>.
def delete
self.class.delete(id) if persisted?
@destroyed = true
freeze
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).
#
# There's a series of callbacks associated with <tt>destroy</tt>. If
# the <tt>before_destroy</tt> callback return +false+ the action is cancelled
# and <tt>destroy</tt> returns +false+. See
# ActiveRecord::Callbacks for further details.
def destroy
raise ReadOnlyRecord if readonly?
destroy_associations
destroy_row if persisted?
@destroyed = true
freeze
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).
#
# There's a series of callbacks associated with <tt>destroy!</tt>. If
# the <tt>before_destroy</tt> callback return +false+ the action is cancelled
# and <tt>destroy!</tt> raises ActiveRecord::RecordNotDestroyed. See
# ActiveRecord::Callbacks for further details.
def destroy!
destroy || raise(ActiveRecord::RecordNotDestroyed)
end
# 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, <tt>Client < Company</tt> to do something
# like render <tt>partial: @client.becomes(Company)</tt> to render that
# instance using the companies/company partial instead of clients/client.
#
# Note: The new instance will share a link to the same attributes as the original class.
# So any change to the attributes in either instance will affect the other.
def becomes(klass)
became = klass.new
became.instance_variable_set("@attributes", @attributes)
became.instance_variable_set("@attributes_cache", @attributes_cache)
became.instance_variable_set("@changed_attributes", @changed_attributes) if defined?(@changed_attributes)
became.instance_variable_set("@new_record", new_record?)
became.instance_variable_set("@destroyed", destroyed?)
became.instance_variable_set("@errors", errors)
became
end
# Wrapper around +becomes+ that also changes the instance's sti column value.
# This is especially useful if you want to persist the changed class in your
# database.
#
# Note: The old instance's sti column value will be changed too, as both objects
# share the same set of attributes.
def becomes!(klass)
became = becomes(klass)
became.public_send("#{klass.inheritance_column}=", klass.sti_name) unless self.class.descends_from_active_record?
became
end
# Updates a single attribute and saves the record.
# This is especially useful for boolean flags on existing records. Also note that
#
# * Validation is skipped.
# * Callbacks are invoked.
# * updated_at/updated_on column is updated if that column is available.
# * Updates all the attributes that are dirty in this object.
#
# This method raises an +ActiveRecord::ActiveRecordError+ if the
# attribute is marked as readonly.
def update_attribute(name, value)
name = name.to_s
verify_readonly_attribute(name)
send("#{name}=", value)
save(validate: false)
end
# Updates the attributes of the model from the passed-in hash and saves the
# record, all wrapped in a transaction. If the object is invalid, the saving
# will fail and false will be returned.
def update(attributes)
# The following transaction covers any possible database side-effects of the
# attributes assignment. For example, setting the IDs of a child collection.
with_transaction_returning_status do
assign_attributes(attributes)
save
end
end
alias update_attributes update
# Updates its receiver just like +update+ but calls <tt>save!</tt> instead
# of +save+, so an exception is raised if the record is invalid.
def update!(attributes)
# The following transaction covers any possible database side-effects of the
# attributes assignment. For example, setting the IDs of a child collection.
with_transaction_returning_status do
assign_attributes(attributes)
save!
end
end
alias update_attributes! update!
# Equivalent to <code>update_columns(name => value)</code>.
def update_column(name, value)
update_columns(name => value)
end
# Updates the attributes directly in the database issuing an UPDATE SQL
# statement and sets them in the receiver:
#
# user.update_columns(last_request_at: Time.current)
#
# This is the fastest way to update attributes because it goes straight to
# the database, but take into account that in consequence the regular update
# procedures are totally bypassed. In particular:
#
# * Validations are skipped.
# * Callbacks are skipped.
# * +updated_at+/+updated_on+ are not updated.
#
# This method raises an +ActiveRecord::ActiveRecordError+ when called on new
# objects, or when at least one of the attributes is marked as readonly.
def update_columns(attributes)
raise ActiveRecordError, "cannot update on a new record object" unless persisted?
attributes.each_key do |key|
verify_readonly_attribute(key.to_s)
end
updated_count = self.class.unscoped.where(self.class.primary_key => id).update_all(attributes)
attributes.each do |k, v|
raw_write_attribute(k, v)
end
updated_count == 1
end
# Initializes +attribute+ to zero if +nil+ and adds the value passed as +by+ (default is 1).
# The increment is performed directly on the underlying attribute, no setter is invoked.
# Only makes sense for number-based attributes. Returns +self+.
def increment(attribute, by = 1)
self[attribute] ||= 0
self[attribute] += by
self
end
# Wrapper around +increment+ that saves the record. This method differs from
# its non-bang version in that it passes through the attribute setter.
# Saving is not subjected to validation checks. Returns +true+ if the
# record could be saved.
def increment!(attribute, by = 1)
increment(attribute, by).update_attribute(attribute, self[attribute])
end
# Initializes +attribute+ to zero if +nil+ and subtracts the value passed as +by+ (default is 1).
# The decrement is performed directly on the underlying attribute, no setter is invoked.
# Only makes sense for number-based attributes. Returns +self+.
def decrement(attribute, by = 1)
self[attribute] ||= 0
self[attribute] -= by
self
end
# Wrapper around +decrement+ that saves the record. This method differs from
# its non-bang version in that it passes through the attribute setter.
# Saving is not subjected to validation checks. Returns +true+ if the
# record could be saved.
def decrement!(attribute, by = 1)
decrement(attribute, by).update_attribute(attribute, self[attribute])
end
# Assigns to +attribute+ the boolean opposite of <tt>attribute?</tt>. So
# if the predicate returns +true+ the attribute will become +false+. This
# method toggles directly the underlying value without calling any setter.
# Returns +self+.
def toggle(attribute)
self[attribute] = !send("#{attribute}?")
self
end
# Wrapper around +toggle+ that saves the record. This method differs from
# its non-bang version in that it passes through the attribute setter.
# Saving is not subjected to validation checks. Returns +true+ if the
# record could be saved.
def toggle!(attribute)
toggle(attribute).update_attribute(attribute, self[attribute])
end
# Reloads the record from the database.
#
# This method finds record by its primary key (which could be assigned manually) and
# modifies the receiver in-place:
#
# account = Account.new
# # => #<Account id: nil, email: nil>
# account.id = 1
# account.reload
# # Account Load (1.2ms) SELECT "accounts".* FROM "accounts" WHERE "accounts"."id" = $1 LIMIT 1 [["id", 1]]
# # => #<Account id: 1, email: 'account@example.com'>
#
# Attributes are reloaded from the database, and caches busted, in
# particular the associations cache.
#
# If the record no longer exists in the database <tt>ActiveRecord::RecordNotFound</tt>
# is raised. Otherwise, in addition to the in-place modification the method
# returns +self+ for convenience.
#
# The optional <tt>:lock</tt> flag option allows you to lock the reloaded record:
#
# reload(lock: true) # reload with pessimistic locking
#
# Reloading is commonly used in test suites to test something is actually
# written to the database, or when some action modifies the corresponding
# row in the database but not the object in memory:
#
# assert account.deposit!(25)
# assert_equal 25, account.credit # check it is updated in memory
# assert_equal 25, account.reload.credit # check it is also persisted
#
# Another common use case is optimistic locking handling:
#
# def with_optimistic_retry
# begin
# yield
# rescue ActiveRecord::StaleObjectError
# begin
# # Reload lock_version in particular.
# reload
# rescue ActiveRecord::RecordNotFound
# # If the record is gone there is nothing to do.
# else
# retry
# end
# end
# end
#
def reload(options = nil)
clear_aggregation_cache
clear_association_cache
fresh_object =
if options && options[:lock]
self.class.unscoped { self.class.lock.find(id) }
else
self.class.unscoped { self.class.find(id) }
end
@attributes.update(fresh_object.instance_variable_get('@attributes'))
@column_types = self.class.column_types
@column_types_override = fresh_object.instance_variable_get('@column_types_override')
@attributes_cache = {}
self
end
# Saves the record with the updated_at/on attributes set to the current time.
# Please note that no validation is performed and only the +after_touch+
# callback is executed.
# If an attribute name is passed, that attribute is updated along with
# updated_at/on attributes.
#
# product.touch # updates updated_at/on
# product.touch(:designed_at) # updates the designed_at attribute and updated_at/on
#
# If used along with +belongs_to+ then +touch+ will invoke +touch+ method on associated object.
#
# class Brake < ActiveRecord::Base
# belongs_to :car, touch: true
# end
#
# class Car < ActiveRecord::Base
# belongs_to :corporation, touch: true
# end
#
# # triggers @brake.car.touch and @brake.car.corporation.touch
# @brake.touch
#
# Note that +touch+ must be used on a persisted object, or else an
# ActiveRecordError will be thrown. For example:
#
# ball = Ball.new
# ball.touch(:updated_at) # => raises ActiveRecordError
#
def touch(name = nil)
raise ActiveRecordError, "cannot touch on a new record object" unless persisted?
attributes = timestamp_attributes_for_update_in_model
attributes << name if name
unless attributes.empty?
current_time = current_time_from_proper_timezone
changes = {}
attributes.each do |column|
column = column.to_s
changes[column] = write_attribute(column, current_time)
end
changes[self.class.locking_column] = increment_lock if locking_enabled?
changed_attributes.except!(*changes.keys)
primary_key = self.class.primary_key
self.class.unscoped.where(primary_key => self[primary_key]).update_all(changes) == 1
end
end
private
# A hook to be overridden by association modules.
def destroy_associations
end
def destroy_row
relation_for_destroy.delete_all
end
def relation_for_destroy
pk = self.class.primary_key
column = self.class.columns_hash[pk]
substitute = self.class.connection.substitute_at(column, 0)
relation = self.class.unscoped.where(
self.class.arel_table[pk].eq(substitute))
relation.bind_values = [[column, id]]
relation
end
def create_or_update
raise ReadOnlyRecord if readonly?
result = new_record? ? create_record : update_record
result != false
end
# Updates the associated record with values matching those of the instance attributes.
# Returns the number of affected rows.
def update_record(attribute_names = @attributes.keys)
attributes_values = arel_attributes_with_values_for_update(attribute_names)
if attributes_values.empty?
0
else
self.class.unscoped.update_record attributes_values, id, id_was
end
end
# Creates a record with values matching those of the instance attributes
# and returns its id.
def create_record(attribute_names = @attributes.keys)
attributes_values = arel_attributes_with_values_for_create(attribute_names)
new_id = self.class.unscoped.insert attributes_values
self.id ||= new_id if self.class.primary_key
@new_record = false
id
end
def verify_readonly_attribute(name)
raise ActiveRecordError, "#{name} is marked as readonly" if self.class.readonly_attributes.include?(name)
end
end
end
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