# Trouble with local variables **URL:** \ **Category:** ruby-talk\ **Created:** [10 October 2009 15:58 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753 "2009-10-10T15:58:17Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Severin\_Newsom](https://avatars.discourse-cdn.com/v4/letter/s/7993a0/32.png) [@Severin\_Newsom](https://rubytalk.org/u/Severin_Newsom)\ **Post date:** [10 October 2009 15:58 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/1 "2009-10-10T15:58:17Z")
Hello everyone! I've been coding with Ruby for about three days, and I just ran into my first big snag. I've been working on a quiz, and the first one had questions like this: puts 'How many classes have a taunt kill?' puts 'A - Three' puts 'B - Four' puts 'C - Five' puts 'D - Six' answer = gets.chomp.downcase if (answer == 'd')   score = score + 1 else end But it's messy, since I have to repeat the code for every question. (I know, I know, DRY). With this in mind, I began construction on quiz2, and used this as my prototype: def check answer = gets.chomp.downcase if (answer == c\_answer)   score = score + 1 else   puts 'The correct answer was ' + c\_answer + '.' end end puts 'Which is the slowest class?' puts 'A - Pyro' puts 'B - Demoman' puts 'C - Heavy' puts 'D - Soldier' c\_answer = 'c' check I understand the problem (mostly), but I'm looking for a workaround. Most of my 'fixes' don't work because of the 'A, B, C, D' system; should that system be changed? Sorry for such a long post, I've just really gotten into this. > **···** > > -- > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). ---
**Author:** ![Bermejo\_Rodrigo](https://avatars.discourse-cdn.com/v4/letter/b/e56c9b/32.png) [@Bermejo\_Rodrigo](https://rubytalk.org/u/Bermejo_Rodrigo)\ **Post date:** [10 October 2009 16:28 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/2 "2009-10-10T16:28:03Z")
Severin Newsom wrote: > Hello everyone! > I've been coding with Ruby for about three days, and I just ran into my > first big snag. I've been working on a quiz, and the first one had > questions like this: > > puts 'How many classes have a taunt kill?' > puts 'A - Three' > puts 'B - Four' > puts 'C - Five' > puts 'D - Six' > answer = gets.chomp.downcase > if (answer == 'd') >   score = score + 1 > else > end > > But it's messy, since I have to repeat the code for every question. (I > know, I know, DRY). With this in mind, I began construction on quiz2, > and used this as my prototype: > > def check > answer = gets.chomp.downcase > if (answer == c\_answer) >   score = score + 1 > else >   puts 'The correct answer was ' + c\_answer + '.' > end > end > puts 'Which is the slowest class?' > puts 'A - Pyro' > puts 'B - Demoman' > puts 'C - Heavy' > puts 'D - Soldier' > c\_answer = 'c' > check > > I understand the problem (mostly), but I'm looking for a workaround. > Most of my 'fixes' don't work because of the 'A, B, C, D' system; should > that system be changed? > > Sorry for such a long post, I've just really gotten into this. read about class variables (or global variables) @score Also it will be cleaner if you pass the answer to chech() tru its argument list def check(answer) ..play around. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Bertram\_Scharpf](https://avatars.discourse-cdn.com/v4/letter/b/43a26b/32.png) [@Bertram\_Scharpf](https://rubytalk.org/u/Bertram_Scharpf)\ **Post date:** [10 October 2009 16:28 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/3 "2009-10-10T16:28:53Z")
Hi, > puts 'A - Pyro' > puts 'B - Demoman' > puts 'C - Heavy' > puts 'D - Soldier' Maybe you do want to do something like that:   def menu ary     letter = "A"     ary.each { |entry|       puts "#{letter} - #{entry}"       letter.succ!     }   end   menu %w(Pyro Demoman Heavy Soldier) Bertram > **···** > > Am Sonntag, 11. Okt 2009, 00:58:17 +0900 schrieb Severin Newsom: > > -- > Bertram Scharpf > Stuttgart, Deutschland/Germany > [http://www.bertram-scharpf.de](http://www.bertram-scharpf.de) ---
**Author:** ![List.rb](https://avatars.discourse-cdn.com/v4/letter/l/f08c70/32.png) [@List.rb](https://rubytalk.org/u/List.rb)\ **Post date:** [10 October 2009 16:45 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/4 "2009-10-10T16:45:49Z")
#checker def correct?(item)   letters = %w(A B C D E F G) puts item[:question] + '?' item[:choices].each\_with\_index {|choice,i| puts "#{letters[i]} - #{choice}" } return item[:solution].call(item[:choices][letters.index(gets.to\_s.strip.chomp.upcase)]) rescue false end #setup correct = 0 questions = [   {     :question =\> "Which is the slowest class",     :choices =\> %w(Pyro Demoman Heavy Soldier),     :solution =\> lambda {|input| input == 'Heavy'}   },   {       :question =\> "What is the best programming language ever",       :choices =\> %w(whitespace ruby),       :solution =\> lambda {|input| input == 'ruby'}   } ] # do work questions.each {|question|   correct +=1 if correct? question } #results puts "correct: #{correct}, incorrect: #{questions.size-correct} score: #{correct/questions.size.to\_f\*100}%" > **···** > > On Sat, Oct 10, 2009 at 11:58 AM, Severin Newsom \wrote: > > > Hello everyone! > > I've been coding with Ruby for about three days, and I just ran into my > > first big snag. I've been working on a quiz, and the first one had > > questions like this: > > > > puts 'How many classes have a taunt kill?' > > puts 'A - Three' > > puts 'B - Four' > > puts 'C - Five' > > puts 'D - Six' > > answer = gets.chomp.downcase > > if (answer == 'd') > > score = score + 1 > > else > > end > > > > But it's messy, since I have to repeat the code for every question. (I > > know, I know, DRY). With this in mind, I began construction on quiz2, > > and used this as my prototype: > > > > def check > > answer = gets.chomp.downcase > > if (answer == c\_answer) > > score = score + 1 > > else > > puts 'The correct answer was ' + c\_answer + '.' > > end > > end > > puts 'Which is the slowest class?' > > puts 'A - Pyro' > > puts 'B - Demoman' > > puts 'C - Heavy' > > puts 'D - Soldier' > > c\_answer = 'c' > > check > > > > I understand the problem (mostly), but I'm looking for a workaround. > > Most of my 'fixes' don't work because of the 'A, B, C, D' system; should > > that system be changed? > > > > Sorry for such a long post, I've just really gotten into this. > > -- > > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Greg\_Barozzi](https://avatars.discourse-cdn.com/v4/letter/g/f6c823/32.png) [@Greg\_Barozzi](https://rubytalk.org/u/Greg_Barozzi)\ **Post date:** [10 October 2009 18:00 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/5 "2009-10-10T18:00:59Z")
Severin Newsom wrote: > Hello everyone! > I've been coding with Ruby for about three days, and I just ran into my > first big snag. I've been working on a quiz, and the first one had > questions like this: > > puts 'How many classes have a taunt kill?' > puts 'A - Three' > puts 'B - Four' > puts 'C - Five' > puts 'D - Six' > answer = gets.chomp.downcase > if (answer == 'd') >   score = score + 1 > else > end > > But it's messy, since I have to repeat the code for every question. (I > know, I know, DRY). With this in mind, I began construction on quiz2, > and used this as my prototype: > > def check > answer = gets.chomp.downcase > if (answer == c\_answer) >   score = score + 1 > else >   puts 'The correct answer was ' + c\_answer + '.' > end > end > puts 'Which is the slowest class?' > puts 'A - Pyro' > puts 'B - Demoman' > puts 'C - Heavy' > puts 'D - Soldier' > c\_answer = 'c' > check > > I understand the problem (mostly), but I'm looking for a workaround. > Most of my 'fixes' don't work because of the 'A, B, C, D' system; should > that system be changed? > > Sorry for such a long post, I've just really gotten into this. Hey! Making a quiz is not something I have ever done, but after reading your post, this is how I would code it up. #I'd start by making an array with all the right answers to the quiz answer\_key = ['a', 'a', 'b', 'd', 'c', 'c'] # for instance # then after printing the question, as you have done above ... answer = answer.push(gets.chomp.downcase) #The above places the input into a new element in the array #Once the quiz is complete we can tally the score like this ... answer\_key.each\_index do |i| score ||= 0 # initialize the variable unless it it already initialized score +=1 if answer\_key[i] == answer[i] end puts "You got #{score} answers correct!" # The each\_index method of the array class returns the index number for # each element of the array so that you can iterate through both arrays # at once, which is pretty cool, I think. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![Brian\_Candler](https://avatars.discourse-cdn.com/v4/letter/b/5f9b8f/32.png) [@Brian\_Candler](https://rubytalk.org/u/Brian_Candler)\ **Post date:** [13 October 2009 10:27 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/6 "2009-10-13T10:27:39Z")
Severin Newsom wrote: > def check > answer = gets.chomp.downcase > if (answer == c\_answer) >   score = score + 1 > else >   puts 'The correct answer was ' + c\_answer + '.' > end > end > puts 'Which is the slowest class?' > puts 'A - Pyro' > puts 'B - Demoman' > puts 'C - Heavy' > puts 'D - Soldier' > c\_answer = 'c' > check > > I understand the problem (mostly) I think you'd find it helpful if you post the actual error you get when you run this program: quiz.rb:3:in `check': undefined local variable or method `c\_answer' for main:Object (NameError)   from quiz.rb:15 This basically tells you the problem: ruby cannot find anything called "c\_answer". This is because c\_answer is a local variable - but methods cannot access local variables defined outside them. Every method defined with 'def' starts with a clean slate as far as local variables are concerned. There are very good reasons for this which I won't go into here. So basically, you either make c\_answer a global variable like $c\_answer (bad practice), or pass it in as an argument to the method (good practice). def check(c\_answer) answer = gets.chomp.downcase if (answer == c\_answer)   score = score + 1 else   puts 'The correct answer was ' + c\_answer + '.' end end puts 'Which is the slowest class?' puts 'A - Pyro' puts 'B - Demoman' puts 'C - Heavy' puts 'D - Soldier' check('c') This moves you along, but if you enter a right answer you get a new error: quiz.rb:4:in `check': undefined method `+' for nil:NilClass (NoMethodError)   from quiz.rb:14 This is the same problem, in this case 'score' is not accessible inside the method. However because you have an assignment to score (score = ...) a local variable is automatically brought into existence with value 'nil', even though the assignment hasn't actually executed yet. This is why you get a potentially confusing error message. "Undefined method... for nil" means you tried to execute nil.something (nil.+ in this case) Again you have a number of options: 1. Have a global variable $score (bad practice, makes it hard to re-use code, non-thread-safe etc) 2. Pass in the old score, and return the new score. This is a "functional" programming style, meaning that your function doesn't actually modify any state, but just returns new calculated values. def check(c\_answer, score)   answer = gets.chomp.downcase   if (answer == c\_answer)     score = score + 1   else     puts 'The correct answer was ' + c\_answer + '.'   end   return score end score = 0 puts 'Which is the slowest class?' puts 'A - Pyro' puts 'B - Demoman' puts 'C - Heavy' puts 'D - Soldier' score = check('c', score) puts "Your score is #{score}" 3. Build a class which holds the state for your quiz session. This is the "object oriented" style. class QuizSession   attr\_accessor :score   def initialize     @score = 0   end   def check(c\_answer)     answer = gets.chomp.downcase     if (answer == c\_answer)       @score = @score + 1     else       puts 'The correct answer was ' + c\_answer + '.'     end   end end session = QuizSession.new puts 'Which is the slowest class?' puts 'A - Pyro' puts 'B - Demoman' puts 'C - Heavy' puts 'D - Soldier' session.check('c') puts "Your score is #{session.score}" I have presented these options making the minimum changes to your existing code. You can think of ways of extending the QuizSession object - for example loading the list of questions from a file, and including the ability to iterate through the questions-and-answers. At the moment, QuizSession is just a score counter and answer checker, but that in itself is a useful function, and a good example of encapsulation (except that it uses 'puts' and so has some user-interface built in as well) You could consider making the user interface a separate object, so that you could plug in a CLI Q&A session, a TK Q&A session, a web-based Q&A session etc. HTH, Brian. > **···** > > -- > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C). ---
**Author:** ![David\_A\_Black1](https://avatars.discourse-cdn.com/v4/letter/d/bcef8e/32.png) [@David\_A\_Black1](https://rubytalk.org/u/David_A_Black1)\ **Post date:** [10 October 2009 17:37 UTC](https://rubytalk.org/t/trouble-with-local-variables/55753/7 "2009-10-10T17:37:39Z")
Hi -- > **···** > > On Sun, 11 Oct 2009, Rodrigo Bermejo wrote: > > > Severin Newsom wrote: > > > > > Hello everyone! > > > I've been coding with Ruby for about three days, and I just ran into my > > > first big snag. I've been working on a quiz, and the first one had > > > questions like this: > > > > > > puts 'How many classes have a taunt kill?' > > > puts 'A - Three' > > > puts 'B - Four' > > > puts 'C - Five' > > > puts 'D - Six' > > > answer = gets.chomp.downcase > > > if (answer == 'd') > > >   score = score + 1 > > > else > > > end > > > > > > But it's messy, since I have to repeat the code for every question. (I > > > know, I know, DRY). With this in mind, I began construction on quiz2, > > > and used this as my prototype: > > > > > > def check > > > answer = gets.chomp.downcase > > > if (answer == c\_answer) > > >   score = score + 1 > > > else > > >   puts 'The correct answer was ' + c\_answer + '.' > > > end > > > puts 'Which is the slowest class?' > > > puts 'A - Pyro' > > > puts 'B - Demoman' > > > puts 'C - Heavy' > > > puts 'D - Soldier' > > > c\_answer = 'c' > > > check > > > > > > I understand the problem (mostly), but I'm looking for a workaround. > > > Most of my 'fixes' don't work because of the 'A, B, C, D' system; should > > > that system be changed? > > > > > > Sorry for such a long post, I've just really gotten into this. > > > > read about class variables (or global variables) > > @score > > @score is an instance variable, not a class or global variable. I > would definitely encourage everyone to learn about class and global > variables, but they're literally about the last thing I would reach > for in almost any situation. You definitely won't need them here. > > David > > -- > The Ruby training with D. Black, G. Brown, J.McAnally > Compleat Jan 22-23, 2010, Tampa, FL > Rubyist [http://www.thecompleatrubyist.com](http://www.thecompleatrubyist.com) > > David A. Black/Ruby Power and Light, LLC ([http://www.rubypal.com](http://www.rubypal.com))