module ActiveEntity::Inheritance::ClassMethods
Attributes
Set this to true
if this is an abstract class (see abstract_class?
). If you are using inheritance with Active Entity and don't want a class to be considered as part of the STI hierarchy, you must set this to true. ApplicationRecord
, for example, is generated as an abstract class.
Consider the following default behaviour:
Shape = Class.new(ActiveEntity::Base) Polygon = Class.new(Shape) Square = Class.new(Polygon) Shape.table_name # => "shapes" Polygon.table_name # => "shapes" Square.table_name # => "shapes" Shape.create! # => #<Shape id: 1, type: nil> Polygon.create! # => #<Polygon id: 2, type: "Polygon"> Square.create! # => #<Square id: 3, type: "Square">
However, when using abstract_class
, Shape
is omitted from the hierarchy:
class Shape < ActiveEntity::Base self.abstract_class = true end Polygon = Class.new(Shape) Square = Class.new(Polygon) Shape.table_name # => nil Polygon.table_name # => "polygons" Square.table_name # => "polygons" Shape.create! # => NotImplementedError: Shape is an abstract class and cannot be instantiated. Polygon.create! # => #<Polygon id: 1, type: nil> Square.create! # => #<Square id: 2, type: "Square">
Note that in the above example, to disallow the creation of a plain Polygon
, you should use validates :type, presence: true
, instead of setting it as an abstract class. This way, Polygon
will stay in the hierarchy, and Active Entity will continue to correctly derive the table name.
Public Instance Methods
Returns whether this class is an abstract class or not.
# File lib/active_entity/inheritance.rb, line 134 def abstract_class? defined?(@abstract_class) && @abstract_class == true end
Returns the class descending directly from ActiveEntity::Base
, or an abstract class, if any, in the inheritance hierarchy.
If A extends ActiveEntity::Base
, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.
If B < A and C < B and if A is an abstract_class
then both B.base_class and C.base_class would return B as the answer since A is an abstract_class.
# File lib/active_entity/inheritance.rb, line 72 def base_class unless self < Base raise ActiveEntityError, "#{name} doesn't belong in a hierarchy descending from ActiveEntity" end if superclass == Base || superclass.abstract_class? self else superclass.base_class end end
Returns whether the class is a base class. See base_class
for more information.
# File lib/active_entity/inheritance.rb, line 86 def base_class? base_class == self end
Returns true
if this does not need STI type condition. Returns false
if STI type condition needs to be applied.
# File lib/active_entity/inheritance.rb, line 54 def descends_from_active_entity? if self == Base false elsif superclass.abstract_class? superclass.descends_from_active_entity? else superclass == Base end end
# File lib/active_entity/inheritance.rb, line 138 def inherited(subclass) subclass.instance_variable_set(:@_type_candidates_cache, Concurrent::Map.new) super end
Determines if one of the attributes passed in is the inheritance column, and if the inheritance column is attr accessible, it initializes an instance of the given subclass instead of the base class.
# File lib/active_entity/inheritance.rb, line 44 def new(attributes = nil, &block) if abstract_class? || self == Base raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated." end super end
Protected Instance Methods
Returns the class type of the record using the current module as a prefix. So descendants of MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.
# File lib/active_entity/inheritance.rb, line 147 def compute_type(type_name) if type_name.start_with?("::") # If the type is prefixed with a scope operator then we assume that # the type_name is an absolute reference. ActiveSupport::Dependencies.constantize(type_name) else type_candidate = @_type_candidates_cache[type_name] if type_candidate && type_constant = ActiveSupport::Dependencies.safe_constantize(type_candidate) return type_constant end # Build a list of candidates to search for candidates = [] name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" } candidates << type_name candidates.each do |candidate| constant = ActiveSupport::Dependencies.safe_constantize(candidate) if candidate == constant.to_s @_type_candidates_cache[type_name] = candidate return constant end end raise NameError.new("uninitialized constant #{candidates.first}", candidates.first) end end