Question

I’m doing my first program, a simple to-do list. I want it to let me type a number, and delete the corresponding item from the list.

Every time though, I get “no implicit conversion from nil to integer”. I can’t seem to work it out. Any ideas?

$list = Array.new

def mainmethod
  puts "Enter new item, or type 'view' to view the list, 'delete' to delete items"
  input = gets.chomp

  if input.downcase == "view"
    puts "Your to do list is as follows:"
    puts $list

  elsif input.downcase == "delete"
    puts "Which item would you like to delete? (Enter a number)"
    deletenumber = gets.chomp.to_i
    deletenumber-=1
    delete_list = [deletenumber]
    delete_list.each do |del|
      $list.delete_at($list.index(del))
    end

  else
    $list << input
    puts "Added to list!"
  end
end

loop { mainmethod }

Answer 1

See http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-delete_at for the proper way of using Array#delete_at.

What you do is calling #index with a number that your array does not contain. Therefore $list.index(del) will return nil and the call to #delete_at will fail.

What you need to do is $list.delete_at(del).