Find all Ruby class descendants: Quick guide

If you are working with Ruby, you may need to find all the descendants of a certain class. This can be particularly useful when you want to check if a class is being used in your project or if you want to perform some operation on all classes that inherit from a specific class.

├Źndice
  1. Using the descendants method
  2. Using the ObjectSpace module
  3. Conclusion

Using the descendants method

The easiest way to find all the descendants of a class in Ruby is by using the descendants method. This method is available on all classes and returns an array of all the classes that inherit from the class you are calling it on.

<!-- language: ruby -->
class MyClass
end

class MyChildClass < MyClass
end

class MyGrandchildClass < MyChildClass
end

MyClass.descendants
# => [MyChildClass, MyGrandchildClass]

In this example, we defined a base class MyClass and two subclasses MyChildClass and MyGrandchildClass that inherit from it. When we call the descendants method on MyClass, it returns an array with both subclasses.

Using the ObjectSpace module

Another way to find all the descendants of a class in Ruby is by using the ObjectSpace module. This module provides a range of methods that allow you to inspect the objects in your Ruby program.

To find all descendants of a class using ObjectSpace, you can iterate through all the objects in the program and check if they are classes that inherit from the class you are interested in:

<!-- language: ruby -->
class MyClass
end

class MyChildClass < MyClass
end

class MyGrandchildClass < MyChildClass
end

descendants = ObjectSpace.each_object(Class).select { |klass| klass < MyClass }
# => [MyChildClass, MyGrandchildClass]

In this example, we defined the same classes as before and used the each_object method from ObjectSpace to iterate through all the objects in the program that are instances of the Class class. We then filtered the classes that inherit from MyClass using the < operator and stored them in the descendants array.

Conclusion

Both the descendants method and the ObjectSpace module can be used to find all the descendants of a class in Ruby. The descendants method is simpler and more efficient, but it may not work with dynamically generated classes or classes that are not loaded yet. The ObjectSpace module provides a more general solution, but it can be slower and may include classes that you are not interested in.

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