我正在尝试学习
scala,并决定创建一个扑克应用程序,让我的头围绕一些类对象.我的甲板工作正常,但我已经到了需要画5张牌的地步.到目前为止,我有：
import util.Random
case class Card(value: Int,color: String)
class Deck {
private var deck = newDeck
def draw(amount: Int): List[Card] = {
val ret = deck.take(amount)
deck = deck.drop(amount)
ret
}
def newDeck: List[Card] = {
Random.shuffle((1 to 13).map(x =>
List(Card(x,"D"),Card(x,"C"),"H"),"S"))).toList.flatten)
}
override def toString: String = "Deck has " + deck.length + " cards left."
}
这个绘图功能看起来似乎没有两个步骤 – 但是我不确定我是否能够(或者应该)拿到顶部多个卡片,并将列表保留在没有这些卡片的状态下？
(顺便说一句,如果某人有更好的甲板创建/洗牌功能,我会全力以赴,这看起来有点像hacky ……但我的主要问题是列表状态)
解决方法
在我看来,你应该重写代码：
(a)具有完全不可变的结构,即NO var,NO可变集合
要么
(b)替换var deck：通过一些可变集合列出[Card],如ListBuffer.
这是(a)解决方案：
import util.Random
case class Card(value: Int,color: String)
class Deck(private val cards: Seq[Card]) {
def draw(amount: Int): (Deck,Seq[Card]) = {
val (ret,rem) = cards.splitAt(amount)
(new Deck(rem),ret)
}
override def toString: String = "Deck has " + cards.size + " cards left."
}
object Deck {
def apply(cards: Seq[Card] = Nil): Deck = cards match {
case Nil =>
val ncds = for(v <- 1 to 13; c <- Seq("D","C","H","S")) yield Card(v,c)
new Deck(Random.shuffle(ncds))
case _ => new Deck(cards)
}
}
使用案例：
scala> :paste // Entering paste mode (ctrl-D to finish) //paste code here // Exiting paste mode,now interpreting. import util.Random defined class Card defined class Deck defined object Deck scala> val d1 = Deck() d1: Deck = Deck has 52 cards left. scala> val (d2,cards) = d1.draw(4) d2: Deck = Deck has 48 cards left. cards: Seq[Card] = Vector(Card(3,H),Card(2,S),Card(11,Card(8,C))
