We often come across situations where
we need to inherit the characteristics
of one class into another class.
Inheritance ensures the “reusability” of codes
as while creating a new class,
we can derive some of the codes from the existing parent class.
This is why Ruby 3.1 has added a new method
called Class#subclasses.
This returns all classes directly inheriting
from the receiver without adding singleton classes.
We can use different implementations from Ruby
via gems to calculate subclasses of a particular class.
The ActiveSupport::DescendantsTracker is one of the implementations
we use in Ruby on Rails.
Finally, Ruby has introduced the Class#subclasses
native implementation
for its latest version of 3.1.
Key terms in Inheritance:
Super class: This is the class whose characteristics are inherited. It is also known as a superclass or base class or parent class.
Sub class: This is the class that is derived from the parent class. It is also known as a subclass or derived class or child class. You can also add its own objects, methods, along with the base class methods and objects, etc.
Note: By default, every class in Ruby has a Super class.
Before Ruby 1.9, the Object class was the Super class
of all the other Sub classes.
Since Ruby 1.9 was introduced, the BasicObject class
is the Super class
of all the other Sub classes in Ruby. Object class
is the Sub class of BasicObject class.
Look at the syntax given below-
subclass_name < superclass_name
After Ruby 3.1
class Animal; end
class Dog < Animal; end
class Cat < Animal; end
class GermanShepherd < Dog; end
class SiberianHusky < Dog; end
Animal.subclasses
=> [Dog, Cat]
Dog.subclasses
=> [GermanShepherd, SiberianHusky]
SiberianHusky.subclasses
=> [ ]To know more about this feature checkout this PR.
