Classes, Objects, and Variables(Chapter 3 of Programming Ruby)

 1 class BookInStock

 2   attr_reader :isbn

 3   attr_accessor :price

 4   def initialize(isbn, price)

 5     @isbn = isbn

 6     @price = Float(price)

 7   end

 8   

 9   def to_s()

     "ISBN: #{@isbn}, Price: #{@price}"

   end

 end

 

 b1 = BookInStock.new("aa", 3)

 p b1

 b2 = BookInStock.new("bb", 2.3)

 p b2

 b3 = BookInStock.new("cc", "5.67")

 puts b3

 puts "ISBN: #{b1.isbn}"

 

book_in_stock.rb

 class BookInStock

   attr_reader :isbn, :price

   def initialize(isbn, price)

     @isbn = isbn

     @price = Float(price)

   end

 end

 

 

csv_reader.rb

 1 require 'csv'

 2 require_relative 'book_in_stock'

 3 class CsvReader

 4   def initialize

 5     @books_in_stock = []

 6   end

 7   def read_in_csv_data(csv_file_name)

 8     CSV.foreach(csv_file_name, headers: true) do |row|

 9       @books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])

     end

   end

   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

 

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}"

 ruby stock_stats.rb test.csv
2 
3 Processing test.csv
4 Total value = 122.07