Module: ActiveRecord::Inheritance::ClassMethods
- Defined in:
- activerecord/lib/active_record/inheritance.rb
Instance Attribute Summary collapse
-
#abstract_class ⇒ Object
Set this to
true
if this is an abstract class (seeabstract_class?
).
Instance Method Summary collapse
-
#abstract_class? ⇒ Boolean
Returns whether this class is an abstract class or not.
-
#base_class ⇒ Object
Returns the class descending directly from ActiveRecord::Base, or an abstract class, if any, in the inheritance hierarchy.
-
#base_class? ⇒ Boolean
Returns whether the class is a base class.
-
#descends_from_active_record? ⇒ Boolean
Returns
true
if this does not need STI type condition. -
#finder_needs_type_condition? ⇒ Boolean
:nodoc:.
- #inherited(subclass) ⇒ Object
-
#new(attributes = nil, &block) ⇒ Object
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.
-
#polymorphic_class_for(name) ⇒ Object
Returns the class for the provided
name
. -
#polymorphic_name ⇒ Object
Returns the value to be stored in the polymorphic type column for Polymorphic Associations.
-
#sti_class_for(type_name) ⇒ Object
Returns the class for the provided
type_name
. -
#sti_name ⇒ Object
Returns the value to be stored in the inheritance column for STI.
Instance Attribute Details
#abstract_class ⇒ Object
Set this to true
if this is an abstract class (see abstract_class?
). If you are using inheritance with Active Record 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(ActiveRecord::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 < ActiveRecord::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 Record will continue to correctly derive the table name.
158 159 160 |
# File 'activerecord/lib/active_record/inheritance.rb', line 158 def abstract_class @abstract_class end |
Instance Method Details
#abstract_class? ⇒ Boolean
Returns whether this class is an abstract class or not.
161 162 163 |
# File 'activerecord/lib/active_record/inheritance.rb', line 161 def abstract_class? defined?(@abstract_class) && @abstract_class == true end |
#base_class ⇒ Object
Returns the class descending directly from ActiveRecord::Base, or an abstract class, if any, in the inheritance hierarchy.
If A extends ActiveRecord::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.
99 100 101 102 103 104 105 106 107 108 109 |
# File 'activerecord/lib/active_record/inheritance.rb', line 99 def base_class unless self < Base raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord" end if superclass == Base || superclass.abstract_class? self else superclass.base_class end end |
#base_class? ⇒ Boolean
Returns whether the class is a base class. See #base_class for more information.
113 114 115 |
# File 'activerecord/lib/active_record/inheritance.rb', line 113 def base_class? base_class == self end |
#descends_from_active_record? ⇒ Boolean
Returns true
if this does not need STI type condition. Returns false
if STI type condition needs to be applied.
76 77 78 79 80 81 82 83 84 |
# File 'activerecord/lib/active_record/inheritance.rb', line 76 def descends_from_active_record? if self == Base false elsif superclass.abstract_class? superclass.descends_from_active_record? else superclass == Base || !columns_hash.include?(inheritance_column) end end |
#finder_needs_type_condition? ⇒ Boolean
:nodoc:
86 87 88 89 |
# File 'activerecord/lib/active_record/inheritance.rb', line 86 def finder_needs_type_condition? #:nodoc: # This is like this because benchmarking justifies the strange :false stuff :true == (@finder_needs_type_condition ||= descends_from_active_record? ? :false : :true) end |
#inherited(subclass) ⇒ Object
199 200 201 202 |
# File 'activerecord/lib/active_record/inheritance.rb', line 199 def inherited(subclass) subclass.instance_variable_set(:@_type_candidates_cache, Concurrent::Map.new) super end |
#new(attributes = nil, &block) ⇒ Object
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.
50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 |
# File 'activerecord/lib/active_record/inheritance.rb', line 50 def new(attributes = nil, &block) if abstract_class? || self == Base raise NotImplementedError, "#{self} is an abstract class and cannot be instantiated." end if has_attribute?(inheritance_column) subclass = subclass_from_attributes(attributes) if subclass.nil? && scope_attributes = current_scope&.scope_for_create subclass = subclass_from_attributes(scope_attributes) end if subclass.nil? && base_class? subclass = subclass_from_attributes(column_defaults) end end if subclass && subclass != self subclass.new(attributes, &block) else super end end |
#polymorphic_class_for(name) ⇒ Object
Returns the class for the provided name
.
It is used to find the class correspondent to the value stored in the polymorphic type column.
195 196 197 |
# File 'activerecord/lib/active_record/inheritance.rb', line 195 def polymorphic_class_for(name) name.constantize end |
#polymorphic_name ⇒ Object
Returns the value to be stored in the polymorphic type column for Polymorphic Associations.
188 189 190 |
# File 'activerecord/lib/active_record/inheritance.rb', line 188 def polymorphic_name base_class.name end |
#sti_class_for(type_name) ⇒ Object
Returns the class for the provided type_name
.
It is used to find the class correspondent to the value stored in the inheritance column.
173 174 175 176 177 178 179 180 181 182 183 184 185 |
# File 'activerecord/lib/active_record/inheritance.rb', line 173 def sti_class_for(type_name) if store_full_sti_class ActiveSupport::Dependencies.constantize(type_name) else compute_type(type_name) end rescue NameError raise SubclassNotFound, "The single-table inheritance mechanism failed to locate the subclass: '#{type_name}'. " \ "This error is raised because the column '#{inheritance_column}' is reserved for storing the class in case of inheritance. " \ "Please rename this column if you didn't intend it to be used for storing the inheritance class " \ "or overwrite #{name}.inheritance_column to use another column for that information." end |
#sti_name ⇒ Object
Returns the value to be stored in the inheritance column for STI.
166 167 168 |
# File 'activerecord/lib/active_record/inheritance.rb', line 166 def sti_name store_full_sti_class ? name : name.demodulize end |