Test whether a Ruby class is a subclass of another class

Confusion picture Confusion · Dec 28, 2010 · Viewed 38.5k times · Source

I would like to test whether a class inherits from another class, but there doesn't seem to exist a method for that.

class A
end

class B < A
end

B.is_a? A 
=> false

B.superclass == A
=> true

A trivial implementation of what I want would be:

class Class
  def is_subclass_of?(clazz)
    return true if superclass == clazz
    return false if self == Object
    superclass.is_subclass_of?(clazz)
  end
end

but I would expect this to exist already.

Answer

Marcel Jackwerth picture Marcel Jackwerth · Dec 28, 2010

Just use the < operator

B < A # => true
A < A # => false

or use the <= operator

B <= A # => true
A <= A # => true