Ruby: Is it possible to determine the class that my Ruby method is executing in without hardcoding the classname?

Question

I am a Nuby to Ruby. I am looking for a way to get the containing Class object of the method of the current line of execution. Is this possible without hardcoding the classname?

# hardcoded example
class A
  def to_s
    "I am a " + A.to_s   # Class "A" is hardcoded here. Is there another way to reference the class A?
  end
end

I thought that maybe self.class would work, but it didn't give me what I was looking for when the class is subclassed.

# Following Outputs=> I am a Camel I am a Camel I am a Camel
# but I want       => I am a Camel I am a Mammal I am a Animal

class Animal
  def to_s
    "I am a " + self.class.to_s
  end
end

class Mammal < Animal
  def to_s
    "I am a " + self.class.to_s + " " + super
  end
end

class Camel < Mammal
  def to_s
    "I am a " + self.class.to_s + " " + super
  end
end

puts Camel.new()

So, is there a keyword, method or something that allows accessing the containing class?

Answer 1

You'll need Class#ancestors :

Camel.ancestors
#=> [Camel, Mammal, Animal, Object, Kernel, BasicObject]

You'll get more classes than you defined, so you'll need to stop at Object :

class Animal
  def to_s
    "I am a " + self.class.ancestors.take_while{|klass| klass != Object}.join(' and a ')
  end
end

class Mammal < Animal
end

class Camel < Mammal
end

puts Animal.new
# => I am a Animal
puts Mammal.new
# => I am a Mammal and a Animal
puts Camel.new
# => I am a Camel and a Mammal and a Animal

ancestors can be Modules or Classes, so if you just want Classes, you can use :

def to_s
  "I am a " + self.class.ancestors.take_while{|klass| klass < Object}.join(' and a ')
end

---

So, is there a keyword, method or something that allows accessing the containing class?

I couldn't find one. Adding

puts method(__method__).owner

to Animal#to_s or Mammal#to_s still returns Camel.

Answer 2

Try this

Class.nesting.first

This gives you the defining class of a method.

class A
  def example
    { defining_class: Class.nesting.first, self_class: self.class }
  end
end

class B < A
end

B.new.example
# => {:defining_class=>A, :self_class=>B}