如何遍历类的成员 [英] How to iterate through members of a class

问题描述

这：

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

赢了不行，因为它试图迭代一个类而不是数组或散列。是否需要迭代所有类的实例？

won't work because it's attempting to iterate over a class rather than an array or hash. Is there a away to iterate over all of the instances of a class?

推荐答案

Ruby不会自动保留对象的引用创建，编写代码是你的责任。例如，在创建新的 Loan 实例时，您将获得一个对象。如果你想在类级别使用每个方法，你需要通过编写捕获它们的代码来跟踪它们：

Ruby doesn't automatically keep references to objects you create, it's your responsibility to write code that does. For example, when creating a new Loan instance you get an object. If you want an each method at the class level you'll need to track these by writing code that captures them:

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，否则垃圾收集器当它们超出范围时，它将拾取并销毁任何未引用的对象。

You must manually retain these because otherwise the garbage collector will pick up and destroy any un-referenced objects when they fall out of scope.

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