设计模式之Iterator

2010-10-06 #设计模式 #Ruby

迭代器模式的百度百科解释:

提供一种方法顺序访问一个聚合对象中各个元素，而又不需暴露该对象的内部表示

Ruby 中可以利用 Enumerable 模块实现each方法:

class Account
  attr_accessor :name, :balance
  
  def initialize(name, balance)
    @name = name
    @balance = balance
  end
  
  def <=>(other)
    balance <=> other.balance
  end
end

class Portfolio
  include Enumerable
  
  def initialize
    @accounts = []
  end
  
  def each(&block)
    @accounts.each(&block)
  end
  
  def add_account(account)
    @accounts << account
  end
end

lucy = Account.new("lucy", 10000)
jack = Account.new("jack", 30000)
portfolio = Portfolio.new
portfolio.add_account(lucy)
portfolio.add_account(jack)	
portfolio.any? {|account| account.balance > 2000}