如何遍历类的成员

Question

这个:

class Loan
    def initialize(amount, interest)
        @amount = amount
        @interest = interest
    end
end

loan1 = Loan.new(100, 0.1)

Loan.each do |amount, interest|
    debt = debt + amount + (amount*interest)
end

将无法工作,因为它试图迭代一个类而不是数组或散列.是否需要迭代一个类的所有实例？

Answer 1

Ruby不会自动保留对您创建的对象的引用,编写代码是您的责任.例如,在创建新Loan实例时,您将获得一个对象.如果你想要一个each类级别的方法,你需要通过编写捕获它们的代码来跟踪它们:

class Loan
  def self.all
    # Lazy-initialize the collection to an empty array
    @all ||= [ ]
  end

  def self.each(&proc)
    @all.each(&proc)
  end

  def initialize(amount, interest)
    @amount = amount
    @interest = interest

    # Force-add this loan to the collection
    Loan.all << self
  end
end

您必须手动保留这些,否则垃圾收集器会在超出范围时拾取并销毁任何未引用的对象.