Question

I am getting this error when I run the following code:

#!/usr/bin/env ruby -rubygems
require File.join(File.dirname(__FILE__), 'authentication')
require "csv" # faster_csv (ruby 1.9)

lines = CSV.read(File.join(File.dirname(__FILE__), 'karaoke.csv')) # Exported an Excel file as CSV
lines.slice!(0) # remove header line
collection = StorageRoom::Collection.find('collection ID')
Song = collection.entry_class
lines.each do |row|
  karaoke = Song.new(:artist => row[0], :song => row[1], :genre => row[2], :file => StorageRoom::File.new_with_filename("#{karaoke.artist}#{karaoke.song}.mov"))
  if karaoke.save
    puts "Misuero Karaoke Latino saved: #{karaoke.artist}, #{karaoke.song}, #{karaoke.genre}"
  else
    puts "Misuero Karaoke Latino could not be saved: #{karaoke.errors.join(', ')}"
  end
end

And the error is:

import_csv.rb:15:in `block in <main>': undefined method `artist' for nil:NilClass (NoMethodError)
    from import_csv.rb:14:in `each'
    from import_csv.rb:14:in `<main>'

I’m interested in learning why this error occurred as well as the solution. Thanks in advance!

Answer 1

Look at line 15 (import_csv.rb:15 tells you where to search for the issue):

karaoke = Song.new(:artist => row[0], :song => row[1], :genre => row[2], 
  :file => StorageRoom::File.new_with_filename("#{karaoke.artist}#{karaoke.song}.mov"))

In the right part of assignment expression you use karaoke.artist and karaoke.song to construct :file part of your Song, but karaoke variable is uninitialized yet (it appears on the left). In fact ruby interpreter defined karaoke variable when it saw the assignment operator and started evaluation of right-hand part of assignment expression (to initialize variable) and failed, because defined variable has nil value.