这是工厂设计模式在C#中的实现吗？

Question

这是我创建信用卡的类库代码。

public abstract class CreditCard
{
    public CardType CardType { get; protected set; }
    public decimal CreditLimit { get; protected set; }
    public decimal AnnualCharge { get; protected set; }
}

public class GoldCreditCard : CreditCard
{
    private GoldCreditCard(decimal creditLimit, decimal annualCharge)
    {
        CardType = CardType.Gold;
        CreditLimit = creditLimit;
        AnnualCharge = annualCharge;
    }

    /// 
    /// Factory pattern
    /// 
    /// 
    public static CreditCard Create()
    {
        return new GoldCreditCard(creditLimit: 15000, annualCharge: 100);
    }
}

public class TitaniumCreditCard : CreditCard
{
    private TitaniumCreditCard(decimal creditLimit, decimal annualCharge)
    {
        CardType = CardType.Titanium;
        CreditLimit = creditLimit;
        AnnualCharge = annualCharge;
    }

    /// 
    /// Factory pattern
    /// 
    /// 
    public static CreditCard Create()
    {
        return new TitaniumCreditCard(creditLimit: 30000, annualCharge: 250);
    }
}

用户界面将是：

    static void Main(string[] args)
    {
        CreditCard card;

        System.Console.WriteLine("Select your card type");
        System.Console.WriteLine("1. Gold Credit Card");
        System.Console.WriteLine("2. Titanium Credit Card");
        var option = System.Console.ReadLine();
        switch (option)
        {

            case "1":
                card = GoldCreditCard.Create();
                PrintCard(card);
                break;
            case "2":
                card = TitaniumCreditCard.Create();
                PrintCard(card);
                break;
            default:
                break;
        }

    }

    static void PrintCard(CreditCard card)
    {
        System.Console.WriteLine($"Your credit card has been successfully created.");
        System.Console.WriteLine($"The credit card type is {card.CardType}.");
        System.Console.WriteLine($"The credit card limit is {card.CreditLimit:C}.");
        System.Console.WriteLine($"The credit card annual fee is {card.AnnualCharge:C}.");
    }

这是工厂设计模式在C#中的实现吗？

Answer 1

在您的实现中，您粉碎了两个不同的角色：Product和Creator。

您的实现相当于以下内容：

public class GoldCreditCard : CreditCard
{
    private GoldCreditCard(decimal creditLimit, decimal annualCharge)
    {
        CardType = CardType.Gold;
        CreditLimit = creditLimit;
        AnnualCharge = annualCharge;
    }

    public GoldCreditCard()
    {
        CardType = CardType.Gold;
        CreditLimit = 15000; 
        AnnualCharge = 100;
    }
}

或者几乎是这样的(这提供了更多的灵活性)：

public class GoldCreditCard : CreditCard
{
    public GoldCreditCard(decimal creditLimit = 15000, decimal annualCharge = 100)
    {
        CardType = CardType.Gold;
        CreditLimit = creditLimit;
        AnnualCharge = annualCharge;
    }
}

模式的全部要点是，只有Creator (Factory)知道如何设置具体的产品。在您的例子中，您的类知道如何初始化自己。