Question

I got confused about the iteration in ruby.In the following code I wrote, I expected that the two paths print out should be the same. But actually they are not. Seems the path was changed in the for loop.

Anything wrong in my code? Thanks

def one_step_search(dest,paths)
  direction = %w(north east south west)
  new_paths = []
  paths.map do |path|

    print "original path is: "
    print_path path

    curr_room = path.last
    for i in 0..3
      new_path = path
      if !curr_room.send("exit_#{direction[i]}").nil?
        next_room_tag = curr_room.send("exit_#{direction[i]}")[0] 
        next_room = find_room_by_tag(next_room_tag)
        if !new_path.include?(next_room)  # don't go back to the room visited before
          new_path << next_room
          new_paths << new_path  
          print "new path is: "
          print_path path
          return new_paths if dest.tag == next_room_tag
        end
      end
    end
  end

  return new_paths
end

Answer 1

It seems to me that problem is in this line

new_path = path

You may think that new_path and path are different objects but it’s not. I’ll illustrate by example:

a = "foo"
b = a
puts a.sub!(/f/, '_')
puts a                   # => "_oo"
puts b                   # => "_oo"

a and b are references that pointing to one object.
The simpliest solution for you will be to use dup or clone

new_path = path.clone

but actually your code requires good cleaning.