Ruby class inheritance issue

Question

I tried to get this result:

Car.class.name # => "Car"
Truck.class.name # => "Truck"
Van.class.name # => "Van" 
Car/Truck/Van.superclass.name # => "Vehicle"

I did this:

require "rspec/autorun"

class Vehicle
end

class Car < Vehicle
end

class Van < Vehicle
end

class Truck < Vehicle
end

describe Car do
  describe ".class.name" do
    it "returns name of the class" do
      expect(Car.class.name).to eq "Car"
    end
  end
end

What am I missing about Ruby's class system in order to implement this?

Have you a link to the coding challenge?

Sagar Pandya
– Sagar Pandya

2018-01-16 17:33:38 +00:00
Commented Jan 16, 2018 at 17:33 — Sagar Pandya
– Sagar Pandya, Commented Jan 16, 2018 at 17:33

Jordan Running · Accepted Answer · 2018-01-16 17:41:28Z

4

Your intuition is good. At face value, the challenge seems incorrect, and if it's intended to be "a relatively simple code challenge," then I think that must be the case.

If the challenge is meant to be tricky, on the other hand, the specified result is certainly something that's possible in Ruby:

class Vehicle
  def self.class
    self
  end
end

class Car < Vehicle; end
class Van < Vehicle; end
class Truck < Vehicle; end

p Car.class.name # => "Car"
p Truck.class.name # => "Truck"
p Van.class.name # => "Van"
p Car.superclass.name # => "Vehicle"

Try it on repl.it: https://repl.it/@jrunning/VisibleMustyHapuka

However, knowing nothing more about the challenge or its source, it's impossible to say whether or not this is the intended solution.

answered Jan 16, 2018 at 17:41

Jordan Running

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3 Comments

Silvio Mayolo Over a year ago

Good observation! Do you know if changing self.class messes anything up with regard to the way the class behaves on other contexts?

ChrisCPO Over a year ago

Yea I knew the Solution was simple, I over complicated it, and I had trouble getting around the "why" factor.

Jordan Running Over a year ago

@SilvioMayolo I would definitely expect this to cause some unusual behavior with code that makes assumptions about the behavior of .class, which is a lot of code in the Ruby ecosystem.

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