2013年12月の買った本リスト

2013_A_shopping_list..rb

class InvalidateCurrencyUnitError < RuntimeError; end;

module CurrencyUnit
  USD = 1
  EURO = 2
  YEN = 3

  def validate_currency_unit(currency_unit)
    if currency_unit == USD; return true; end;
    if currency_unit == EURO; return true; end;
    if currency_unit == YEN; return true; end;
    false
  end
  module_function :validate_currency_unit

  /*為替変換メソッドとか作る*/
end


class Money
  attr_reader :amount, :currency_unit
  def initialize(currency_unit, amount)
    @amount = amount
    if CurrencyUnit.validate_currency_unit(currency_unit) then
      @currency_unit = currency_unit
    else
      raise InvalidateCurrencyUnitError
    end
  end

  def to_s
    case @currency_unit
      when CurrencyUnit::USD
        "$#{@amount} USD"
      when CurrencyUnit::EURO
        "€#{@amount} EURO"
      when CurrencyUnit::YEN
        "#{@amount} JYN"
      else
        "#{@amount}"
      end
  end
end

class Book
  attr_reader :price, :publisher
  def initialize(publisher, title, price)
    @publisher = publisher
    @title = title
    if price.kind_of?(Money) then
      @price = price
    else
      raise "InvalidateArguments"
    end
  end

  def to_s
<<"TO_S"
PUBLISHER   : #{@publisher}
TITLE       : #{@title}
PRICE       : #{@price.to_s}
TO_S
  end
end

books = Array.new
books.push(Book.new("O'reilly", 'ruby under a microscope', Money.new(CurrencyUnit::USD, 12.78)))
books.push(Book.new("O'reilly", 'physics for game developers, 2nd edition', Money.new(CurrencyUnit::USD, 14.40)))
books.push(Book.new("O'reilly", 'an introduction to the mathematics of finance, 2nd edition', Money.new(CurrencyUnit::USD, 31.98)))
books.push(Book.new("O'reilly", 'head first statistics', Money.new(CurrencyUnit::USD, 11.20)))
books.push(Book.new('apress', 'expert f# 3.0', Money.new(CurrencyUnit::USD, 15)))
books.push(Book.new('apress', 'beginning haskell', Money.new(CurrencyUnit::USD, 15)))
books.push(Book.new('manning publications', 'java 8 lambdas in action', Money.new(CurrencyUnit::USD, 19.99)))
books.push(Book.new('the pragmatic bookshelf', 'build awesome command-line applications in ruby 2', Money.new(CurrencyUnit::USD, 22.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'explore it!', Money.new(CurrencyUnit::USD, 23.00 / 2)))
books.push(Book.new('the pragmatic bookshelf', 'functional programming patterns in scala and clojure', Money.new(CurrencyUnit::USD, 24.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'good math', Money.new(CurrencyUnit::USD, 24.00 / 2)))
books.push(Book.new('the pragmatic bookshelf', 'modern c++ programming with test-driven development', Money.new(CurrencyUnit::USD, 26.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'node.js the right way', Money.new(CurrencyUnit::USD, 11.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'programming elixir', Money.new(CurrencyUnit::USD, 24.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'seven concurrency models in seven weeks', Money.new(CurrencyUnit::USD, 25.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'seven web frameworks in seven weeks', Money.new(CurrencyUnit::USD, 25.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'the healthy programmer', Money.new(CurrencyUnit::USD, 24.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'web development with clojure', Money.new(CurrencyUnit::USD, 24.00 / 2 )))
books.push(Book.new('the pragmatic bookshelf', 'working with ruby threads', Money.new(CurrencyUnit::USD, 29.00 / 2)))

books.each{|book|
  puts book.to_s
  puts ""
}

amount = 0
books.each{|book|
  amount += book.price.amount
}
puts Money.new(CurrencyUnit::USD, amount).to_s

oreilly_amount = 0
oreilly_books = books.select{|book| book.publisher == "O'reilly"}
oreilly_books.each{|book|
          oreilly_amount += book.price.amount
          }
puts Money.new(CurrencyUnit::USD, oreilly_amount).to_s