Question

If a class has been previously defined, how can I tell it to inherit from a class Parent?

For instance:

class Parent
  ..
end

class Klass
  ..
end

Now I want it to inherit from Parent.

I can’t re-open the class and set it because I will get a class mismatch error:

class Klass < Parent
  ..
end

Specifically, I am trying to find out how to set the class inheritance on a class I am creating through Object.const_set.

klass = Object.const_set('Klass', Class.new)

How can I tell Klass to inherit from class Parent?

Answer 1

There is no way to change the superclass of an already existing class.

To specifiy the superclass of a class you’re creating dynamically, you simply pass the superclass as an argument to Class.new.

class Parent
end
klass = Class.new(Parent)
klass.superclass #=> Parent

Just as a side note: You’re not creating the class with const_set. You’re creating it with Class.new. You’re simply storing the created class in a constant with const_set. Once const_set is invoked, Class.new has already happened and the superclass cannot be changed anymore.