Check your Ruby Developer Level with simple task

I just found an old post from @evanilukhin showing interview task - Simple word calculator. I was reading it on my mobile, so first I read his post, and decided to not look at the answer code (anyway it's impossible to understand on small android display).

Ruby Interview Tasks - Simple word calculator

Ivan Ilyukhin ・ Dec 23 '19 ・ 1 min read

#ruby

Task is next: make this code work:

one.plus.two.equal    # =>  3
one.minus.three.equal # => -2

While you're on interview, it can be harder than it should be. Few minutes later electricity came back (some works during this morning... awful), so I decided to try to solve it (in his post I read it's good for every developer to check his skills... and it's true). You have a link to his post if you want to read it and see his results (probably better than mine, but hey, 10 minutes on android 5, and it works... :P).

So what do you think, are you able to make this code work without reading the rest? Here's my solution (first one, fast one):

My Answer

  class One
    def initialize
      @num = 1
    end

    def plus
      @opt = :add
      return self
    end

    def minus
      @opt = :rmw
      return self
    end

    def two
      case @opt
        when :add then @num += 2
        when :rmw then @num -= 2
      end
      return self
    end

    def three
      case @opt
        when :add then @num += 3
        when :rmw then @num -= 3
      end
      return self
    end

    def equal
      num  = @num
      @num = 1
      return num
    end
  end

  one = One.new
  one.plus.two.equal    =>  3
  one.minus.three.equal => -2

and about 10 minutes later I decided to make this more DRY, and to allow it to use 'one' chained more times (like original article code work)

  class One
    def initialize
      @num = 1
    end

    def one
      use_number 1
    end

    def two
      use_number 2
    end

    def three
      use_number 3
    end

    def plus;  set_opt(:add) end
    def minus; set_opt(:rmw) end

    def equal
      num  = @num and @num = 1
      return num
    end

    private

    def set_opt(opt)
      @opt = opt; return self
    end

    def use_number(number)
      case @opt
        when :add then @num += number.to_i
        when :rmw then @num -= number.to_i
        else @num
      end
      @opt = nil
      return self
    end
  end

one = One.new
one.plus.two.equal # => 3
one.plus.two.minus.three.plus.one.equal => 1