Ruby Koans Scoring Project. undefined method `length' for nil:NilClass

I am BRAND new to Ruby, and programing in general. I'm working my way through the Ruby Koans. I've made it up to 176/274 before getting stuck.

It's the "Scoring Project" I need to write a method to calculate the score of a given dice roll.

Th开发者_运维知识库is may not be the most elegant code you've ever seen but here's what I came up with:

def score(dice)
  tally = 0
  tally += (dice.sort.to_s[/[1]+/].length % 3) * 100
  if dice.sort.to_s[/[1]+/].length >= 3
    tally += 1000
  end
  tally = tally + (dice.sort.to_s[/[5]+/].length % 3) * 50
  if dice.sort.to_s[/[5]+/].length >= 3
    tally += 500
  end
  if dice.sort.to_s[/[2]+/].length >= 3
    tally += 200
  end
  if dice.sort.to_s[/[3]+/].length >= 3
    tally += 300
  end
  if dice.sort.to_s[/[4]+/].length >= 3
    tally += 400
  end
  if dice.sort.to_s[/[6]+/].length >= 3
    tally += 600
  end
  return tally
end

The first test is: score([]) needs to return 0

When I run it I get "undefined method `length' for nil:NilClass" (the line referenced is the first instance of .length) This tells me that "dice.sort.to_s[/[1]+/]" with "score([])" is nil, but when i run it in irb>> it is 0.

What gives?

OK. Got it.

Huge apologies, I had said that running "dice.sort.to_s[/[1]+/]" was returning zero not nil, it must have been because it had some storred value i didn't know about. When i ran "[].sort.to_s[/[1]+/]" it returned nil properly. So I nested each of my if statements in a check to make sure there wasn't a nil value.

def score(dice)
  tally = 0
  if dice.sort.to_s[/[1]+/]
    tally += (dice.sort.to_s[/[1]+/].length % 3) * 100
    if dice.sort.to_s[/[1]+/].length >= 3
      tally += 1000
    end
  end
  if dice.sort.to_s[/[5]+/]
    tally += (dice.sort.to_s[/[5]+/].length % 3) * 50
    if dice.sort.to_s[/[5]+/].length >= 3
      tally += 500
    end
  end
  if dice.sort.to_s[/[2]+/]
    if dice.sort.to_s[/[2]+/].length >= 3
      tally += 200
    end
  end
  if dice.sort.to_s[/[3]+/]
    if dice.sort.to_s[/[3]+/].length >= 3
      tally += 300
    end
  end
  if dice.sort.to_s[/[4]+/]
    if dice.sort.to_s[/[4]+/].length >= 3
      tally += 400
    end
  end
  if dice.sort.to_s[/[6]+/]
    if dice.sort.to_s[/[6]+/].length >= 3
      tally += 600
    end
  end
  return tally
end

All test's pass.

What Ruby version are you using? I'm using 1.9.2 and my IRB gives me the same error since the regexp returns nil if there is no match. Being dice = [] a border case, you could add a check for that on the first lines of your code in order to return 0 then.

I did the RubyKoans today and even though, my code is not prettier than yours, maybe it'll help you out a bit:

def score(dice)

points = 0
dice.sort!
  nmbrs = Array.new
       dice.each { |n|
               nmbrs[n] = dice.select { |nm| nm == n}
       } 

 n = 0
 nmbrs.each { |vals|
      n = n + 1
      if(vals.nil?)
              next
      end
      if(vals.count >= 3)

              points += (n-1)*100 if (n-1) != 1
              points += 1000 if (n-1) == 1

              if vals.size > 3
                      if (n-1) == 1
                              points += 100 * (vals.size - 3)
                      else
                              if (n-1) == 5
                                      points += 50 * (vals.size - 3)
                            end
                      end

              end
      else
            points += 100 * (vals.count) if (n-1) == 1
            points += 50 * (vals.count) if (n-1) == 5
      end
   }

    points

 end

Sorry about the crappy function, but it does work, so it might give you an idea of how to solve that particular problem.

Good luck!