Why doesn't relative_require work on Ruby 1.8.6? - ruby

Question

I'm learning Ruby (using version 1.8.6) on Windows 7.
When I try to run the stock_stats.rb program below, I get the following error:
C:\Users\Will\Desktop\ruby>ruby stock_stats.rb
stock_stats.rb:1: undefined method `require_relative' for main:Object (NoMethodE
rror)
I have three v.small code files:
stock_stats.rb
require_relative 'csv_reader'
reader = CsvReader.new
ARGV.each do |csv_file_name|
STDERR.puts "Processing #{csv_file_name}"
reader.read_in_csv_data(csv_file_name)
end
puts "Total value = #{reader.total_value_in_stock}"
csv_reader.rb
require 'csv'
require_relative 'book_in_stock'
class CsvReader
def initialize
#books_in_stock = []
end
def read_in_csv_data(csv_file_name)
CSV.foreach(csv_file_name, headers: true) do |row|
#books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])
end
end
# later we'll see how to use inject to sum a collection
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
sum
end
def number_of_each_isbn
# ...
end
end
book_in_stock.rb
require 'csv'
require_relative 'book_in_stock'
class CsvReader
def initialize
#books_in_stock = []
end
def read_in_csv_data(csv_file_name)
CSV.foreach(csv_file_name, headers: true) do |row|
#books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])
end
end
# later we'll see how to use inject to sum a collection
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
sum
end
def number_of_each_isbn
# ...
end
end
Thanks in advance for any help.

Answer 1

require_relative doesn't exist in your version of Ruby. You could upgrade Ruby, install the backports gem and require 'backports/1.9.1/kernel/require/relative' but the easiest fix will be to change your require to:
require File.join(File.dirname(__FILE__), 'csv_reader')

Answer 2

Edit:
Back in the days where this question was asked it referred to Ruby 1.8.6 where there was no require_relative. By now Ruby 1.8.6 is outdated and shouldn't be used anymore.
Original:
There is simply no method name require_relative. You can use require there aswell.
The require_relative function is included in an extension project to the Ruby core libraries, found here: http://www.rubyforge.org/projects/extensions
You should be able to install them with gem install extensions.
Then in your code add the following line before the require_relative:
require 'extensions/all'