Module: ActiveEntity::Inheritance::ClassMethods

Defined in:
lib/active_entity/inheritance.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

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 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.



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# File 'lib/active_entity/inheritance.rb', line 131

def abstract_class
  @abstract_class
end

Instance Method Details

#abstract_class? ⇒ Boolean

Returns whether this class is an abstract class or not.

Returns:

  • (Boolean) 


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# File 'lib/active_entity/inheritance.rb', line 134

def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end

#base_class ⇒ Object

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.



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# 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

#base_class? ⇒ Boolean

Returns whether the class is a base class. See #base_class for more information.

Returns:

  • (Boolean) 


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# File 'lib/active_entity/inheritance.rb', line 86

def base_class?
  base_class == self
end

#descends_from_active_entity? ⇒ Boolean

Returns true if this does not need STI type condition. Returns false if STI type condition needs to be applied.

Returns:

  • (Boolean) 


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# 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

#inherited(subclass) ⇒ Object 



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# File 'lib/active_entity/inheritance.rb', line 138

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.



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# 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