为什么我的卡片阵列是空的？

Question

我是一名新手编码员，正在为我的班级学习 C#，但在练习练习时遇到了麻烦，我们必须制作一副纸牌并将它们分发出去。

我们需要创建一个类，通过构造函数从另一个类接收参数来创建卡片。然后在 Tostring 方法中使用这些值通过 switch 语句设置这些卡片的值和花色并返回一张卡片。在第二个类中，我们用卡片填充数组，并在 Dealing 方法中调用 Tostring 方法，通过将卡片从数组中拉出，随机生成用户指定数量的卡片。

问题是我的数组没有被填充我试图 Console.WriteLine 数组的部分在它们被分配之后直接被分配并且它们是空的。你不必给我完整的答案，只要让我走上正轨。

代码如下：

这是卡片创建类

 `  class Card
{

    static int value; 
    static int suit;
    static string cdvalue;
    static string cdsuit;

    string card;

    public Card(int ranvalue, int ransuit) //constructor that sets value and suit
    {
        value = ranvalue;
        suit = ransuit;
    }
    public override string ToString()
    {
        switch (value) //switch statement for card value
        {
            case 1: cdvalue = "ace";
                break;
            case 2: cdvalue = "two";
                break;
            case 3: cdvalue = "three";
                break;
            case 4: cdvalue = "four";
                break;
            case 5: cdvalue = "five";
                break;
            case 6: cdvalue = "six";
                break;
            case 7: cdvalue = "seven";
                break;
            case 8: cdvalue = "eight";
                break;
            case 9: cdvalue = "nine";
                break;
            case 10: cdvalue = "ten";
                break;
            case 11: cdvalue = "jack";
                break;
            case 12: cdvalue = "queen";
                break;
            case 13: cdvalue = "king";
                break;
        }
        switch (suit) // switch for card suit
        {
            case 1: cdsuit = "Hearts ";
                break;
            case 2: cdsuit = "Spades ";
                break;
            case 3: cdsuit = "Diamonds ";
                break;
            case 4: cdsuit = "Clubs ";
                break;
        }
        card = cdvalue + " of " + cdsuit;

        return card;// returns a string in the form of "value of suit"`

这个类创建卡组

class Deck
{
    Random rng = new Random(); //Random object



    private static Card[] deck;
    static string[] cards; 
    public Deck()
    {
        deck = new Card[52];//creates array of 52 elements
        int l = 0;
        for (int i = 1; i <= 13; i++)//loops to create cards 
        {
            for (int j = 1; j <= 4; j++)
            {

                deck[l++] = new Card(i,j); // populates the array with all 52 cards



            }
        }

    }
    static string dealt;
    static int Rndm;
    public string deal(int number)//parameter received from user
    {
        cards = new string[number];//creates an array to contain dealt card objects
        int m = 0;

        for (int num=0;num<number;num++) // determines the amount of cards to be dealt
        {

            Rndm = rng.Next(0,53);
            cards[m++] = deck[Rndm].ToString();//fills the card array with randomly dealt cards from the deck
            dealt = string.Join(" ", cards); // turns the card array into a single string of the cards dealt



        }
        return dealt;//returns the cards dealt

这是测试类

  static void Main(string[] args)
    {

        // get the number of cards from the user - must be between 1 and 52
        int cardsDealt = -1;
        do
        {
            Console.Write("Enter number of cards to get (1-52): ");
            String dealStr = Console.ReadLine();
            Boolean parsed = int.TryParse(dealStr, out cardsDealt);
        } while (cardsDealt < 1 || cardsDealt > 52);

        // create a Deck object
        Deck cardDeck = new Deck();

        // Call the deal method
        String cards = cardDeck.deal(cardsDealt);

        // List the result
        Console.WriteLine("\nCards dealt:\n" + cards);

Answer 1

在您的 Card 类中，变量 value 和 suit 标记为 static。

private static int value;
private static int suit;

因为这两个变量是静态的，所以对这些变量的引用将在 Card 对象的实例之间保持不变。这意味着每次创建新的 Card 对象时，您都会无意中更新所有其他 Card 对象 value 和 suit 具有相同值的变量。因此，现在无论何时您获得 Card 的实例，它将与所有其他实例（创建的最后一张 Card）相同。

从这些声明中删除 static 关键字，你应该没问题。

另外我建议阅读静态以更熟悉它的用法：Static keyword in c#

Answer 2

您的代码非常接近正确。您似乎对何时使用static 有误解。

如果您需要一个在类的所有实例之间共享的变量，请使用static。但是，如果您需要每个实例的值，则不需要。

您的代码中没有变量应该是static。

此外，为了帮助您编写代码，您无需在类级别定义所有变量。可以（并且应该）在每个方法中声明很多内容。

这是代码的重构版本，以便您了解应该做什么。

void Main()
{
    // get the number of cards from the user - must be between 1 and 52
    int cardsDealt = -1;
    while (cardsDealt < 1 || cardsDealt > 52)
    {
        Console.Write("Enter number of cards to get (1-52): ");
        String dealStr = Console.ReadLine();
        Boolean parsed = int.TryParse(dealStr, out cardsDealt);
    }

    // create a Deck object
    Deck cardDeck = new Deck();

    // Call the deal method
    String cards = cardDeck.deal(cardsDealt);

    // List the result
    Console.WriteLine("\nCards dealt:\n" + cards);
}

public class Card
{
    private int value;
    private int suit;

    public Card(int ranvalue, int ransuit) //constructor that sets value and suit
    {
        value = ranvalue;
        suit = ransuit;
    }
    public override string ToString()
    {
        string cdvalue = null;
        switch (value) //switch statement for card value
        {
            case 1:
                cdvalue = "ace";
                break;
            case 2:
                cdvalue = "two";
                break;
            case 3:
                cdvalue = "three";
                break;
            case 4:
                cdvalue = "four";
                break;
            case 5:
                cdvalue = "five";
                break;
            case 6:
                cdvalue = "six";
                break;
            case 7:
                cdvalue = "seven";
                break;
            case 8:
                cdvalue = "eight";
                break;
            case 9:
                cdvalue = "nine";
                break;
            case 10:
                cdvalue = "ten";
                break;
            case 11:
                cdvalue = "jack";
                break;
            case 12:
                cdvalue = "queen";
                break;
            case 13:
                cdvalue = "king";
                break;
        }
        string cdsuit = null;
        switch (suit) // switch for card suit
        {
            case 1:
                cdsuit = "Hearts ";
                break;
            case 2:
                cdsuit = "Spades ";
                break;
            case 3:
                cdsuit = "Diamonds ";
                break;
            case 4:
                cdsuit = "Clubs ";
                break;
        }
        string card = cdvalue + " of " + cdsuit;
        return card;// returns a string in the form of "value of suit"`
    }
}

public class Deck
{
    private Random rng = new Random(); //Random object
    private Card[] deck;

    public Deck()
    {
        deck = new Card[52];//creates array of 52 elements
        int l = 0;
        for (int i = 1; i <= 13; i++)//loops to create cards 
        {
            for (int j = 1; j <= 4; j++)
            {
                deck[l++] = new Card(i, j); // populates the array with all 52 cards
            }
        }
    }

    public string deal(int number)//parameter received from user
    {
        string[] cards = new string[number];//creates an array to contain dealt card objects
        for (int num = 0; num < number; num++) // determines the amount of cards to be dealt
        {
            int Rndm = rng.Next(deck.Length);
            cards[num] = deck[Rndm].ToString();//fills the card array with randomly dealt cards from the deck
        }
        string dealt = string.Join(" ", cards); // turns the card array into a single string of the cards dealt
        return dealt;//returns the cards dealt
    }
}

唯一的另一个问题是您的发牌代码会产生重​​复的牌。您可能需要为此做点什么。

---

如果我编写这个代码，我会这样做：

public class Card
{
    private int value;
    private int suit;
    public Card(int ranvalue, int ransuit)
    {
        value = ranvalue;
        suit = ransuit;
    }
    public override string ToString()
    {
        var values = new []
        {
            "ace", "two", "three", "four", "five", "six", "seven",
            "eight", "nine", "ten", "jack", "queen", "king"
        };
        var suits = new []
        {
            "Hearts", "Spades", "Diamonds", "Clubs"
        };
        return String.Format("{0} of {1}", values[value - 1], suits[suit - 1]);
    }
}

public class Deck
{
    private Random rng = new Random();
    private Card[] deck;

    public Deck()
    {
        deck =
        (
            from value in Enumerable.Range(1, 13)
            from suit in Enumerable.Range(1, 4)
            select new Card(value, suit)
        ).ToArray();
    }

    public string deal(int number)
    {
        string dealt = string.Join(" ", deck.OrderBy(x => rng.Next()).Take(number));
        return dealt;
    }
}

这解决了重复卡问题。