Ruby Koans:测试两组具有相同值的不同骰子 [英] Ruby Koans : Test two different sets of dices who have same values

问题描述

我正在研究Ruby Koans(Ruby的一个教程项目).在 About_Dice_Project 中，需要创建一个名为 DiceSet 的类.我成功了，但是有一个有趣的问题.

I am working through the Ruby Koans(A tutorial project of Ruby). In the About_Dice_Project, it's demanded to create a class named DiceSet. I succeed, but there is a interesting question.

这是代码:

class DiceSet

  # Attribute reader
  attr_reader :values

  # Initializer
  def initialize
    @values = []
  end

  # Roll method
  def roll(dice_amount)
    @values = Array.new(dice_amount) { rand(1..6) }
  end
end

这个测试很有趣:

def test_dice_values_should_change_between_rolls
    dice = DiceSet.new

    dice.roll(5)
    first_time = dice.values

    dice.roll(5)
    second_time = dice.values

    assert_not_equal first_time, second_time,
      "Two rolls should not be equal"
  end

关于它的思考:

THINK ABOUT IT:

如果掷骰是随机的，则有可能(尽管不是 可能)两个连续的掷骰子是相等的.那会是什么 更好的方法对此进行测试?

If the rolls are random, then it is possible (although not likely) that two consecutive rolls are equal. What would be a better way to test this?

我的想法是使用以下命令测试first_time和second_time的 object_id assert_not_equal first_time.object_id, second_time.object_id.可以，但是我是对的吗?作为Ruby和编程的初学者，object_id的确是什么? 顺便说一句，是否有可能在markdown中证明文本的正确性?

My idea is to test the object_id of first_time and second_time, using assert_not_equal first_time.object_id, second_time.object_id. It works but am i right ? As a beginner in Ruby and programming, what is an object_id indeed ? By the way, is it possible to justify the text in markdown ?

任何帮助将不胜感激！

推荐答案

object_ids和相等性

您不应该比较object_id，而应该比较value.

a = [1, 2, 3]
b = [1, 2, 3]

puts a == b
#=> true
puts a.object_id == b.object_id
#=> false

通过比较object_id，您正在测试变量是否指向完全相同的对象.在您的情况下，first_time和second_time是彼此独立创建的，因此它们不能引用同一对象.它们可以具有相同的值.

By comparing object_ids, you're testing if variables refer to the exact same object. In your case, first_time and second_time are created independently from each others, so they cannot reference the same object. They can have the same values, though.

一种确保两个连续掷骰不相等的方法是使用while循环:

One way to ensure that no two consecutive rolls are equal would be to use a while loop :

class DiceSet
  # Attribute reader
  attr_reader :values

  # Initializer
  def initialize
    @values = []
    @last_values = []
  end

  # Roll method
  def roll(dice_amount)
    while @values == @last_values
      @values = Array.new(dice_amount) { rand(1..6) }
    end
    @last_values = @values
    @values
  end
end

dice = DiceSet.new

dice.roll(5)
first_time = dice.values

dice.roll(5)
second_time = dice.values # <-- cannot be equal to first_time

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