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Active Record Persistence

Namespace
Methods
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Instance Public methods
becomes(klass)

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.

Note: The new instance will share a link to the same attributes as the original class. Therefore the sti column value will still be the same. Any change to the attributes on either instance will affect both instances. If you want to change the sti column as well, use becomes! instead.

# File activerecord/lib/active_record/persistence.rb, line 211
def becomes(klass)
  became = klass.new
  became.instance_variable_set("@attributes", @attributes)
  changed_attributes = @changed_attributes if defined?(@changed_attributes)
  became.instance_variable_set("@changed_attributes", changed_attributes || {})
  became.instance_variable_set("@new_record", new_record?)
  became.instance_variable_set("@destroyed", destroyed?)
  became.instance_variable_set("@errors", errors)
  became
end
becomes!(klass)

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.

# File activerecord/lib/active_record/persistence.rb, line 228
def becomes!(klass)
  became = becomes(klass)
  sti_type = nil
  if !klass.descends_from_active_record?
    sti_type = klass.sti_name
  end
  became.public_send("#{klass.inheritance_column}=", sti_type)
  became
end
decrement(attribute, by = 1)

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.

# File activerecord/lib/active_record/persistence.rb, line 341
def decrement(attribute, by = 1)
  self[attribute] ||= 0
  self[attribute] -= by
  self
end
decrement!(attribute, by = 1)

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.

# File activerecord/lib/active_record/persistence.rb, line 351
def decrement!(attribute, by = 1)
  decrement(attribute, by).update_attribute(attribute, self[attribute])
end
delete()

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.

Note that this will also delete records marked as readonly?.

To enforce the object's before_destroy and after_destroy callbacks or any :dependent association options, use #destroy.

# File activerecord/lib/active_record/persistence.rb, line 166
def delete
  self.class.delete(id) if persisted?
  @destroyed = true
  freeze
end
destroy()

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

There's a series of callbacks associated with destroy. If the before_destroy callback throws :abort the action is cancelled and destroy returns false. See ActiveRecord::Callbacks for further details.

# File activerecord/lib/active_record/persistence.rb, line 179
def destroy
  raise ReadOnlyRecord, "#{self.class} is marked as readonly" if readonly?
  destroy_associations
  self.class.connection.add_transaction_record(self)
  destroy_row if persisted?
  @destroyed = true
  freeze
end
destroy!()

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

There's a series of callbacks associated with destroy!. If the before_destroy callback throws :abort the action is cancelled and destroy! raises ActiveRecord::RecordNotDestroyed. See ActiveRecord::Callbacks for further details.

# File activerecord/lib/active_record/persistence.rb, line 195
def destroy!
  destroy || raise(RecordNotDestroyed.new("Failed to destroy the record", self))
end
destroyed?()

Returns true if this object has been destroyed, otherwise returns false.

# File activerecord/lib/active_record/persistence.rb, line 91
def destroyed?
  sync_with_transaction_state
  @destroyed
end
increment(attribute, by = 1)

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.

# File activerecord/lib/active_record/persistence.rb, line 324
def increment(attribute, by = 1)
  self[attribute] ||= 0
  self[attribute] += by
  self
end
increment!(attribute, by = 1)

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.

# File activerecord/lib/active_record/persistence.rb, line 334
def increment!(attribute, by = 1)
  increment(attribute, by).update_attribute(attribute, self[attribute])
end
new_record?()

Returns true if this object hasn't been saved yet – that is, a record for the object doesn't exist in the database yet; otherwise, returns false.

# File activerecord/lib/active_record/persistence.rb, line 85
def new_record?
  sync_with_transaction_state
  @new_record
end
persisted?()

Returns true if the record is persisted, i.e. it's not a new record and it was not destroyed, otherwise returns false.

# File activerecord/lib/active_record/persistence.rb, line 98
def persisted?
  sync_with_transaction_state
  !(@new_record || @destroyed)
end
reload(options = nil)

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 and the QueryCache.

If the record no longer exists in the database ActiveRecord::RecordNotFound is raised. Otherwise, in addition to the in-place modification the method returns self for convenience.

The optional :lock 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
# File activerecord/lib/active_record/persistence.rb, line 420
def reload(options = nil)
  self.class.connection.clear_query_cache

  fresh_object =
    if options && options[:lock]
      self.class.unscoped { self.class.lock(options[:lock]).find(id) }
    else
      self.class.unscoped { self.class.find(id) }
    end

  @attributes = fresh_object.instance_variable_get('@attributes')
  @new_record = false
  self
end
save(*args)

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.

By default, save also sets the updated_at/updated_on attributes to the current time. However, if you supply touch: false, these timestamps will not be updated.

There's a series of callbacks associated with save. If any of the before_* callbacks throws :abort 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.

# File activerecord/lib/active_record/persistence.rb, line 124
def save(*args)
  create_or_update(*args)
rescue ActiveRecord::RecordInvalid
  false
end
save!(*args)

Saves the model.

If the model is new, a record gets created in the database, otherwise the existing record gets updated.

With save! validations always run. If any of them fail ActiveRecord::RecordInvalid gets raised. See ActiveRecord::Validations for more information.

By default, save! also sets the updated_at/updated_on attributes to the current time. However, if you supply touch: false, these timestamps will not be updated.

There's a series of callbacks associated with save!. If any of the before_* callbacks throws :abort the action is cancelled and save! raises ActiveRecord::RecordNotSaved. See ActiveRecord::Callbacks for further details.

Attributes marked as readonly are silently ignored if the record is being updated.

# File activerecord/lib/active_record/persistence.rb, line 150
def save!(*args)
  create_or_update(*args) || raise(RecordNotSaved.new("Failed to save the record", self))
end
toggle(attribute)

Assigns to attribute the boolean opposite of attribute?. So if the predicate returns true the attribute will become false. This method toggles directly the underlying value without calling any setter. Returns self.

# File activerecord/lib/active_record/persistence.rb, line 359
def toggle(attribute)
  self[attribute] = !public_send("#{attribute}?")
  self
end
toggle!(attribute)

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.

# File activerecord/lib/active_record/persistence.rb, line 368
def toggle!(attribute)
  toggle(attribute).update_attribute(attribute, self[attribute])
end
touch(*names, time: nil)

Saves the record with the updated_at/on attributes set to the current time or the time specified. Please note that no validation is performed and only the after_touch, after_commit and after_rollback callbacks are executed.

This method can be passed attribute names and an optional time argument. If attribute names are passed, they are updated along with updated_at/on attributes. If no time argument is passed, the current time is used as default.

product.touch                         # updates updated_at/on with current time
product.touch(time: Time.new(2015, 2, 16, 0, 0, 0)) # updates updated_at/on with specified time
product.touch(:designed_at)           # updates the designed_at attribute and updated_at/on
product.touch(:started_at, :ended_at) # updates started_at, ended_at and updated_at/on attributes

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
# File activerecord/lib/active_record/persistence.rb, line 469
def touch(*names, time: nil)
  raise ActiveRecordError, "cannot touch on a new record object" unless persisted?

  time ||= current_time_from_proper_timezone
  attributes = timestamp_attributes_for_update_in_model
  attributes.concat(names)

  unless attributes.empty?
    changes = {}

    attributes.each do |column|
      column = column.to_s
      changes[column] = write_attribute(column, time)
    end

    clear_attribute_changes(changes.keys)
    primary_key = self.class.primary_key
    scope = self.class.unscoped.where(primary_key => _read_attribute(primary_key))

    if locking_enabled?
      locking_column = self.class.locking_column
      scope = scope.where(locking_column => _read_attribute(locking_column))
      changes[locking_column] = increment_lock
    end

    result = scope.update_all(changes) == 1

    if !result && locking_enabled?
      raise ActiveRecord::StaleObjectError.new(self, "touch")
    end

    result
  else
    true
  end
end
update(attributes)

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.

Also aliased as: update_attributes
# File activerecord/lib/active_record/persistence.rb, line 260
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
update!(attributes)

Updates its receiver just like update but calls save! instead of save, so an exception is raised if the record is invalid.

Also aliased as: update_attributes!
# File activerecord/lib/active_record/persistence.rb, line 273
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
update_attribute(name, value)

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.

See also update_column.

# File activerecord/lib/active_record/persistence.rb, line 250
def update_attribute(name, value)
  name = name.to_s
  verify_readonly_attribute(name)
  public_send("#{name}=", value)
  save(validate: false) if changed?
end
update_attributes(attributes)
Alias for: update
update_attributes!(attributes)
Alias for: update!
update_column(name, value)

Equivalent to update_columns(name => value).

# File activerecord/lib/active_record/persistence.rb, line 285
def update_column(name, value)
  update_columns(name => value)
end
update_columns(attributes)

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:

This method raises an ActiveRecord::ActiveRecordError when called on new objects, or when at least one of the attributes is marked as readonly.

# File activerecord/lib/active_record/persistence.rb, line 304
def update_columns(attributes)
  raise ActiveRecordError, "cannot update a new record" if new_record?
  raise ActiveRecordError, "cannot update a destroyed record" if destroyed?

  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