Module: Torque::PostgreSQL::Base::ClassMethods

Defined in:: lib/torque/postgresql/base.rb

Instance Method Summary collapse

#belongs_to_many(name, scope = nil, **options) ⇒ Object

Specifies a one-to-many association.
#inherited(subclass) ⇒ Object

Wenever it’s inherited, add a new list of auxiliary statements It also adds an auxiliary statement to load inherited records’ relname.

Instance Method Details

#belongs_to_many(name, scope = nil, **options) ⇒ `Object`

Specifies a one-to-many association. The following methods for retrieval and query of collections of associated objects will be added:

collection is a placeholder for the symbol passed as the name argument, so belongs_to_many :tags would add among others tags.empty?.

collection: Returns a Relation of all the associated objects. An empty Relation is returned if none are found.
collection<<(object, …): Adds one or more objects to the collection by adding their ids to the array of ids on the parent object. Note that this operation instantly fires update SQL without waiting for the save or update call on the parent object, unless the parent object is a new record. This will also run validations and callbacks of associated object(s).
collection.delete(object, …): Removes one or more objects from the collection by removing their ids from the list on the parent object. Objects will be in addition destroyed if they’re associated with dependent: :destroy, and deleted if they’re associated with dependent: :delete_all.
collection.destroy(object, …): Removes one or more objects from the collection by running destroy on each record, regardless of any dependent option, ensuring callbacks are run. They will also be removed from the list on the parent object.
collection=objects: Replaces the collections content by deleting and adding objects as appropriate.
collection_singular_ids: Returns an array of the associated objects’ ids
collection_singular_ids=ids: Replace the collection with the objects identified by the primary keys in ids. This method loads the models and calls collection=. See above.
collection.clear: Removes every object from the collection. This destroys the associated objects if they are associated with dependent: :destroy, deletes them directly from the database if dependent: :delete_all, otherwise just remove them from the list on the parent object.
collection.empty?: Returns true if there are no associated objects.
collection.size: Returns the number of associated objects.
collection.find(…): Finds an associated object according to the same rules as ActiveRecord::FinderMethods#find.
collection.exists?(…): Checks whether an associated object with the given conditions exists. Uses the same rules as ActiveRecord::FinderMethods#exists?.
collection.build(attributes = {}, …): Returns one or more new objects of the collection type that have been instantiated with attributes and linked to this object by adding its id to the list after saving.
collection.create(attributes = {}): Returns a new object of the collection type that has been instantiated with attributes, linked to this object by adding its id to the list after performing the save (if it passed the validation).
collection.create!(attributes = {}): Does the same as collection.create, but raises ActiveRecord::RecordInvalid if the record is invalid.
collection.reload: Returns a Relation of all of the associated objects, forcing a database read. An empty Relation is returned if none are found.

Example

A Video class declares belongs_to_many :tags, which will add:

Video#tags (similar to Tag.where([id] && tag_ids))
Video#tags<<
Video#tags.delete
Video#tags.destroy
Video#tags=
Video#tag_ids
Video#tag_ids=
Video#tags.clear
Video#tags.empty?
Video#tags.size
Video#tags.find
Video#tags.exists?(name: 'ACME')
Video#tags.build
Video#tags.create
Video#tags.create!
Video#tags.reload

The declaration can also include an options hash to specialize the behavior of the association.

Options

:class_name

Specify the class name of the association. Use it only if that name can’t be inferred from the association name. So belongs_to_many :tags will by default be linked to the Tag class, but if the real class name is SpecialTag, you’ll have to specify it with this option.

:foreign_key

Specify the foreign key used for the association. By default this is guessed to be the name of this class in lower-case and “_ids” suffixed. So a Video class that makes a #belongs_to_many association with Tag will use “tag_ids” as the default :foreign_key.

It is a good idea to set the :inverse_of option as well.

:primary_key

Specify the name of the column to use as the primary key for the association. By default this is id.

:dependent

Controls what happens to the associated objects when their owner is destroyed. Note that these are implemented as callbacks, and Rails executes callbacks in order. Therefore, other similar callbacks may affect the :dependent behavior, and the :dependent behavior may affect other callbacks.

:touch

If true, the associated objects will be touched (the updated_at/on attributes set to current time) when this record is either saved or destroyed. If you specify a symbol, that attribute will be updated with the current time in addition to the updated_at/on attribute. Please note that with touching no validation is performed and only the after_touch, after_commit and after_rollback callbacks are executed.

:optional

When set to true, the association will not have its presence validated.

:required

When set to true, the association will also have its presence validated. This will validate the association itself, not the id. You can use :inverse_of to avoid an extra query during validation. NOTE: required is set to false by default and is deprecated. If you want to have association presence validated, use required: true.

:default

Provide a callable (i.e. proc or lambda) to specify that the association should be initialized with a particular record before validation.

:inverse_of

Specifies the name of the #has_many association on the associated object that is the inverse of this #belongs_to_many association. See ActiveRecord::Associations::ClassMethods’s overview on Bi-directional associations for more detail.

Option examples:

belongs_to_many :tags, dependent: :nullify
belongs_to_many :tags, required: true, touch: true
belongs_to_many :tags, default: -> { Tag.default }

# File 'lib/torque/postgresql/base.rb', line 201

def belongs_to_many(name, scope = nil, **options)
  reflection = Associations::Builder::BelongsToMany.build(self, name, scope, options)
  ::ActiveRecord::Reflection.add_reflection(self, name, reflection)
end

#inherited(subclass) ⇒ `Object`

Wenever it’s inherited, add a new list of auxiliary statements It also adds an auxiliary statement to load inherited records’ relname

# File 'lib/torque/postgresql/base.rb', line 15

def inherited(subclass)
  super

  subclass.class_attribute(:auxiliary_statements_list)
  subclass.auxiliary_statements_list = {}

  record_class = ActiveRecord::Relation._record_class_attribute

  # Define helper methods to return the class of the given records
  subclass.auxiliary_statement record_class do |cte|
    pg_class = ::Arel::Table.new('pg_class')
    arel_query = ::Arel::SelectManager.new(pg_class)
    arel_query.project(pg_class['oid'], pg_class['relname'].as(record_class.to_s))

    cte.query 'pg_class', arel_query.to_sql
    cte.attributes col(record_class) => record_class
    cte.join tableoid: :oid
  end

  # Define the dynamic attribute that returns the same information as
  # the one provided by the auxiliary statement
  subclass.dynamic_attribute(record_class) do
    next self.class.table_name unless self.class.physically_inheritances?

    pg_class = ::Arel::Table.new('pg_class')
    source = ::Arel::Table.new(subclass.table_name, as: 'source')
    quoted_id = ::Arel::Nodes::Quoted.new(self.class.connection.quote(id))

    query = ::Arel::SelectManager.new(pg_class)
    query.join(source).on(pg_class['oid'].eq(source['tableoid']))
    query.where(source[subclass.primary_key].eq(quoted_id))
    query.project(pg_class['relname'])

    self.class.connection.select_value(query)
  end
end