Question

好像我的代码永远不会通过switch语句运行。每次我创建一个Deck对象时，每个Card对象的套装和名称都是nil。任何人都可以帮助我吗？

class Card
def initialize (suit, number, name)
    @suit = suit
    @number = number
    @name = name         #
end
attr_reader :suit, :number, :name
end

class Deck
      def initialize
          @deck = Array.new
          for i in 0...4
              suit = case i
                  when i == 0 then "Spades"
                  when i == 1 then "Hearts"
                  when i == 2 then "Diamonds"
                  when i == 3 then "Clubs"
              end
          puts i
          puts suit     #Debug only
          for j in 2...15
              name = case j
                  when j == 2 then "Two of #{suit}"
                  when j == 3 then "Three of #{suit}"
                  when j == 4 then "Four of #{suit}"
                  when j == 5 then "Five of #{suit}"
                  when j == 6 then "Six of #{suit}"
                  when j == 7 then "Seven of #{suit}"
                  when j == 8 then "Eight of #{suit}"
                  when j == 9 then "Nine of #{suit}"
                  when j == 10 then "Ten of #{suit}"
                  when j == 11 then "Jack of #{suit}"
                  when j == 12 then "Queen of #{suit}"
                  when j == 13 then "King of #{suit}"
                  when j == 14 then "Ace of #{suit}"
              end
              puts j
              puts name   #Debug only
              @deck.push(Card.new(suit, j, name))
          end
      end
  end
  attr_reader :deck    
end

Answer 1

case语句隐式应用===运算符。所以你想要更像的东西：

case j
when 2 then "Two of #{suit}"
when 3 then "Three of #{suit}"
# ...
end

Answer 2

你的case语句不应该包含实际的布尔比较，而应该是文字，比如：

case j
when 2
 "Two of #{suit}"
when 3
 "Three of #{suit}"
end

Answer 3

没有理由开始使用case。你甚至不需要哈希，一对阵列就可以了：

suits = %w{Spades Hearts Diamonds Clubs}
values = %w{- - Two Three Four Five Six Seven Eight Nine Ten Jack Queen King Ace}
deck = suits.map do |s|
  (2..14).map do |i|
    Card.new(s,i,"#{values[i]} of #{s}")
  end
end.flatten

Answer 4

Jeremy和Cody已经回答正确了。只是另一种观点：

你对i == 0的when子句测试。这个比较返回true或false。因此，当您测试为true时，您的代码可以正常工作：

[0,1,2,3 ].each{|i|
  print "Test #{i}. Hit: "
  case true
      when i == 0 then puts  "Spades"
      when i == 1 then puts "Hearts"
      when i == 2 then puts "Diamonds"
      when i == 3 then puts "Clubs"
    end
}

请不要使用这样的代码。它可能有用，但这是无稽之谈。使用Jeremy和Cody已发布的代码：

[0,1,2,3 ].each{|i|
  print "Test #{i}. Hit: "
  case i
      when 0 then puts  "Spades"
      when 1 then puts "Hearts"
      when 2 then puts "Diamonds"
      when 3 then puts "Clubs"
    end
}

需要有关Ruby案例陈述的帮助

4 个答案: