module ActiveRecord::Persistence - activerecord-4.2.3 Documentation

# module ActiveRecord::Persistence

# Active Record Persistence¶ ↑

### Public Instance Methods

becomes(klass) click to toggle source

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. So any change to the attributes in either instance will affect the other.

    # File lib/active_record/persistence.rb, line 198
    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) click to toggle source

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 lib/active_record/persistence.rb, line 215
    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) click to toggle source

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 lib/active_record/persistence.rb, line 328
    def decrement(attribute, by = 1)
      self[attribute] ||= 0
      self[attribute] -= by
      self
    end

decrement!(attribute, by = 1) click to toggle source

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 lib/active_record/persistence.rb, line 338
    def decrement!(attribute, by = 1)
      decrement(attribute, by).update_attribute(attribute, self[attribute])
    end

delete() click to toggle source

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 `:dependent` association options, use `#destroy`.

    # File lib/active_record/persistence.rb, line 155
    def delete
      self.class.delete(id) if persisted?
      @destroyed = true
      freeze
    end

destroy() click to toggle source

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 return `false` the action is cancelled and `destroy` returns `false`. See ActiveRecord::Callbacks for further details.

    # File lib/active_record/persistence.rb, line 168
    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!() click to toggle source

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 return `false` the action is cancelled and `destroy!` raises ActiveRecord::RecordNotDestroyed. See ActiveRecord::Callbacks for further details.

    # File lib/active_record/persistence.rb, line 184
    def destroy!
      destroy || raise(RecordNotDestroyed.new("Failed to destroy the record", self))
    end

destroyed?() click to toggle source

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

    # File lib/active_record/persistence.rb, line 91
    def destroyed?
      sync_with_transaction_state
      @destroyed
    end

increment(attribute, by = 1) click to toggle source

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 lib/active_record/persistence.rb, line 311
    def increment(attribute, by = 1)
      self[attribute] ||= 0
      self[attribute] += by
      self
    end

increment!(attribute, by = 1) click to toggle source

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 lib/active_record/persistence.rb, line 321
    def increment!(attribute, by = 1)
      increment(attribute, by).update_attribute(attribute, self[attribute])
    end

new_record?() click to toggle source

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 lib/active_record/persistence.rb, line 85
    def new_record?
      sync_with_transaction_state
      @new_record
    end

persisted?() click to toggle source

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

    # File lib/active_record/persistence.rb, line 98
    def persisted?
      !(new_record? || destroyed?)
    end

reload(options = nil) click to toggle source

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 lib/active_record/persistence.rb, line 407
    def reload(options = nil)
      clear_aggregation_cache
      clear_association_cache
      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(*) click to toggle source

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 `before_*` 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.

    # File lib/active_record/persistence.rb, line 119
    def save(*)
      create_or_update
    rescue ActiveRecord::RecordInvalid
      false
    end

save!(*) click to toggle source

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.

There's a series of callbacks associated with `save!`. If any of the `before_*` callbacks return `false` 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 lib/active_record/persistence.rb, line 141
    def save!(*)
      create_or_update || raise(RecordNotSaved.new("Failed to save the record", self))
    end

toggle(attribute) click to toggle source

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 lib/active_record/persistence.rb, line 346
    def toggle(attribute)
      self[attribute] = !send("#{attribute}?")
      self
    end

toggle!(attribute) click to toggle source

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 lib/active_record/persistence.rb, line 355
    def toggle!(attribute)
      toggle(attribute).update_attribute(attribute, self[attribute])
    end

touch(*names) click to toggle source

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`, `after_commit` and `after_rollback` callbacks are executed.

If attribute names are passed, they are 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
    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 lib/active_record/persistence.rb, line 455
    def touch(*names)
      raise ActiveRecordError, "cannot touch on a new record object" unless persisted?

      attributes = timestamp_attributes_for_update_in_model
      attributes.concat(names)

      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?

        clear_attribute_changes(changes.keys)
        primary_key = self.class.primary_key
        self.class.unscoped.where(primary_key => self[primary_key]).update_all(changes) == 1
      else
        true
      end
    end

update(attributes) click to toggle source

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.

    # File lib/active_record/persistence.rb, line 247
    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

Also aliased as: update_attributes
update!(attributes) click to toggle source

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

    # File 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

Also aliased as: update_attributes!
update_attribute(name, value) click to toggle source

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 lib/active_record/persistence.rb, line 237
    def update_attribute(name, value)
      name = name.to_s
      verify_readonly_attribute(name)
      send("#{name}=", value)
      save(validate: false)
    end

update_attributes(attributes)
Alias for: update
update_attributes!(attributes)
Alias for: update!
update_column(name, value) click to toggle source

Equivalent to `update_columns(name => value)`.

    # File lib/active_record/persistence.rb, line 272
    def update_column(name, value)
      update_columns(name => value)
    end

update_columns(attributes) click to toggle source

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.

    # File lib/active_record/persistence.rb, line 291
    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

### Private Instance Methods

_create_record(attribute_names = self.attribute_names) click to toggle source

Creates a record with values matching those of the instance attributes and returns its id.

    # File lib/active_record/persistence.rb, line 521
    def _create_record(attribute_names = self.attribute_names)
      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

_update_record(attribute_names = self.attribute_names) click to toggle source

Updates the associated record with values matching those of the instance attributes. Returns the number of affected rows.

    # File lib/active_record/persistence.rb, line 510
    def _update_record(attribute_names = self.attribute_names)
      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

create_or_update() click to toggle source

    # File lib/active_record/persistence.rb, line 502
    def create_or_update
      raise ReadOnlyRecord, "#{self.class} is marked as readonly" if readonly?
      result = new_record? ? _create_record : _update_record
      result != false
    end

destroy_associations() click to toggle source

A hook to be overridden by association modules.

    # File lib/active_record/persistence.rb, line 483
    def destroy_associations
    end

destroy_row() click to toggle source

    # File lib/active_record/persistence.rb, line 486
    def destroy_row
      relation_for_destroy.delete_all
    end

relation_for_destroy() click to toggle source

    # File lib/active_record/persistence.rb, line 490
    def relation_for_destroy
      pk         = self.class.primary_key
      column     = self.class.columns_hash[pk]
      substitute = self.class.connection.substitute_at(column)

      relation = self.class.unscoped.where(
        self.class.arel_table[pk].eq(substitute))

      relation.bind_values = [[column, id]]
      relation
    end

verify_readonly_attribute(name) click to toggle source

    # File lib/active_record/persistence.rb, line 531
    def verify_readonly_attribute(name)
      raise ActiveRecordError, "#{name} is marked as readonly" if self.class.readonly_attributes.include?(name)
    end