title: Accessing Hash Keys with user inputted variables, NoMethodError
body: <p>I get this error message when trying to access a hash with user inputted variables: "undefined method `index' for nil:NilClass (NoMethodError)"</p>
  
  <p>This should illustrate my problem a little better... once the string "n" is stored in a variable that variable can't access the hash anymore and returns nil.  Why?</p>
  
  <pre><code> [6] pry(main)&gt; line = "n"
  =&gt; "n"
  [7] pry(main)&gt; subway[:line]
  =&gt; nil
  [8] pry(main)&gt; subway[:"n"]
  =&gt; ["timessquare", "34th", "28th", "23rd", "unionsquare", "8th"]
  [9] pry(main)&gt; line
  =&gt; "n"
  
  This is the .rb file
  
  
  
  n = ["timessquare", "34th","28th","23rd","unionsquare","8th"]
  l = ["8th", "6th", "unionsquare","3rd","1st"]
  six = ["grandcentral","33rd","28th","23rd","unionsquare","astorplace"]
  
  subway = {:n=&gt;n, :l=&gt; l, :six=&gt;six}
  
  
  puts "Where would you like to go?"
  destination = gets.strip.chomp.downcase.delete(" ")
  
  
  
  puts "What line is that on?"
  endline = gets.strip.chomp.downcase.delete(" ")
  
  
  puts "What station will you be departing from?"
  location = gets.strip.chomp.downcase.delete(" ")
  
  
  puts "What line is that on?"
  startline = gets.strip.chomp.downcase.delete(" ")
  
  
  if startline == endline
      puts (startline.index(destination)-startline.index(location)).abs
  else
      puts "You have #{(subway[:startline].index(location) - subway[:startline].index("unionsquare")).abs} stops until transfer"
      puts "After you have #{(subway[:endline].index(destination) - subway[:endline]index("unionsquare")).abs} until your destination"    
  end    
  </code></pre>