Keep getting main:Object (NameError)

1

I want to write a code in Ruby that reads in information from a file and prints it out as an array in the terminal. This is what I have so far:

class Track
attr_accessor :name, :location

def initialize (name, location)
	@name = name
	@location = location
end

end

def read_tracks(music_file)

count = music_file.gets().to_i()
i=0
tracks = Array.new()
while (i<count)
track = read_track(music_file)
tracks << track
i+=1
end

return tracks
end

def read_track(a_file)
track_name=a_file.gets.chomp
track_location = a_file.gets.chomp
track = Track.new(track_name, track_location)
track.name= track_name
track.location= track_location
return track

end

def print_tracks(tracks)
index = 0
while (index<tracks.length)
print_track tracks[index]
index+=1
end
end

def print_track(track)
puts('Track title is: ’ + track.title)
puts('Track file location is: ’ + track.location)
end

def main()
a_file = File.new(“input.txt”, “r”) # open for reading

print_tracks(tracks)
end

main()

But I keep getting the following error: Traceback (most recent call last):
1: from track_file_handling.rb:68:in <main>' track_file_handling.rb:65:in main’: undefined local variable or method
`tracks’ for main:Object (NameError)
I am relatively new to ruby so I cannot figure out why this is happening. Any feedback on whether my code can actually do what I want it to will also be appreciated.

2

Read through your ‘main’ method:

def main()
  a_file = File.new(“input.txt”, “r”) # open for reading

  print_tracks(tracks)
end

It first opens a file to read, and names it a_file.
Then it calls print_tracks passing it the value of variable tracks. But tracks is not defined, hence your error.

I suspect you are missing a call to read_tracks …

3

Hi pcl. Thank you for your reply. I was able to get my code running thanks to your suggestion. However, it now printing out the output twice instead of once. For example. it is printing out:
Crackling Rose
sounds/01-Cracklin-rose.wav
Soolaimon
sounds/06-Soolaimon.wav
Sweet Caroline
sounds/20-Sweet_Caroline.wav
Crackling Rose
sounds/01-Cracklin-rose.wav
Soolaimon
sounds/06-Soolaimon.wav
Sweet Caroline
sounds/20-Sweet_Caroline.wav

instead of just:
Crackling Rose
sounds/01-Cracklin-rose.wav
Soolaimon
sounds/06-Soolaimon.wav
Sweet Caroline
sounds/20-Sweet_Caroline.wav

Why might this be?

4

However, it now printing out the output twice instead of once.

I don’t see any reason - it looks like print_tracks is being called twice. Take a look at main and see where/how it is printing.

Incidentally:

  1. in your read_track method, you don’t have to set the values for the track name and location - you have passed them to the constructor, and the initialize method stores them into fields. It is simpler to write:
def read_track(a_file)
  track_name=a_file.gets.chomp
  track_location = a_file.gets.chomp
  return Track.new(track_name, track_location)
end
  1. in print_track you first try to print track.title -> this should be track.name.
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