CODEWITHSUNDEEP
arraysrubywhile-loopnomethoderror
Mike
Mike

Reputation: 1

Ruby programming why is While loop generating a (NoMethodError)?

I'm a relatively new Ruby student, and though I can tell it's never going to be a language I prefer I would like to at least understand it because its a gateway language. For my project we are instructed to solve a maze thats passed into a multi-dimensional array. We haven't learned recursion or any advanced techniques. This is an overview. My specific issue in my code is that in my while loop I am getting the error message for a value I'm passing into my array.

rb:60 in `: undefined method `[]' for nil:NilClass (NoMethodError) from -e:1:in `load'

I did research for an hour or so and it means that the value I'm passing into my array is nil, but I've assigned it a value. My code is below. I've isolated it to the row variable that is causing it to throw the error, but I have assigned row a value, and that passes through fine. it's when I use row+=1 that it throws the error I think. (Though i could be incorrect.) I'm also asking my teacher about this but he hasn't responded so I thought I would post it here as well in hopes of finding a solution for the error. 

maze=[]

def main_menu (options)
options.each_with_index do |option, index|

printf("%-s. %-s\n", "#{index+1}", "#{option}")
end
print "Please make a selection:"
main_selection=gets.to_i
return main_selection
end

menu_selection=["Maze 1", "Maze 2", "Maze 3", "Maze 4", "Maze 5", "Maze 6", "Maze 7", "Maze 8", "Maze 9", "Maze 10", "Quit"]
user_selection=0
path=1
row=0
column=0
while user_selection != menu_selection.length
user_selection=main_menu(menu_selection)
puts user_selection
case user_selection
when 1
  maze.clear
  mz_file=File.open("maze1.mz")

  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  mz_file.close
  maze.each do |row|
    puts row.join
  end

  maze.each_index do |row|
    column = maze[row].index "F"
    if column
      maze[row+1][column]=0
      maze[row-1][column]=0
      maze[row][column+1]=0
      maze[row][column-1]=0
    end
  end
  maze.each do |row|
    puts row.join
  end

  #WHILE LOOP FOR MAZE

  while row <=maze[0].length
    column=0
    while column <= maze.length
      if maze[row][column]== 0
        maze[row+1][column]==path
        maze[row-1][column]==path
        maze[row][column+1]==path
        maze[row][column-1]==path
      end
      column=column+1
    end
    row=row+1
  end
  maze.each do |row|
    puts row.join
  end
when 2
  maze.clear
  mz_file=File.open("maze2.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 3
  maze.clear
  mz_file=File.open("maze3.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 4
  maze.clear
  mz_file=File.open("maze4.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 5
  maze.clear
  mz_file=File.open("maze5.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 6
  maze.clear
  mz_file=File.open("maze6.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 7
  maze.clear
  mz_file=File.open("maze7.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 8
  maze.clear
  mz_file=File.open("maze8.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 9
  maze.clear
  mz_file=File.open("maze9.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
when 10
  maze.clear
  mz_file=File.open("maze10.mz")
  while !mz_file.eof?
    line=mz_file.gets.chomp.split("")
    maze.push line
  end
  maze.each do |row|
    puts row.join
  end
  mz_file.close
 end
end

Upvotes: 0

Views: 178

Answers (1)

pjs
pjs

Reputation: 19855

You have a lot of problems in here. Your indentations are all wrong, which would help you track down some issues such as unclosed loops/blocks (which are an issue in the code you posted). You're shadowing your row variable multiple times with loop indices, you're failing to strip white space before checking string responses (which is almost certainly putting some nils into your array), you are using == for what appear to be assignments around 50 lines into your program, you're using <= to test an array index against a length.

Try testing your small tasks, such as reading a line of input and splitting it, in irb. That gives you direct and immediate feedback if there's a problem with the way you're doing business. You should also consider using an editor or IDE that will help you with indentation and do some sanity checks on things like the =='s where you appear to want assignment.

Upvotes: 4

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