工廠模式-C#改良實現

參考了下網上的工廠模式實現，總的來講例子仍是OK得，可是示例太單一了，所以我作了下優化的改良實現。

namespace DP
{
    public interface ICreditCard
    {
        string GetCardType();
        int GetCreditLimit();
        int GetAnnualCharge();
    }

    //Concrete Product 1
    public class MoneyBackCreditCard : ICreditCard
    {
        public string GetCardType()
            => "MoneyBack";
        public int GetCreditLimit()
            => 15000;
        public int GetAnnualCharge()
            => 500;
    }
    //Concrete Product 2
    public class TitaniumCreditCard : ICreditCard
    {
        public string GetCardType()
            => "Titanium";
        public int GetCreditLimit()
            => 25000;
        public int GetAnnualCharge()
            => 1500;
    }
    //Concrete Product 3
    public class PlatinumCreditCard : ICreditCard
    {
        public string GetCardType() => "Platinum";
        public int GetCreditLimit() => 35000;
        public int GetAnnualCharge() => 2000;
    }
    
    public abstract class CreditCardFactory
    {
        protected abstract ICreditCard MakeProduct();

        public ICreditCard CreateCreditCard() => MakeProduct();
    }

    public class MoneyBackFactory : CreditCardFactory
    {
        protected override ICreditCard MakeProduct() => new MoneyBackCreditCard();
    }

    public class PlatinumFactory : CreditCardFactory
    {
        protected override ICreditCard MakeProduct() => new PlatinumCreditCard();
    }


    public class TitaniumFactory : CreditCardFactory
    {
        protected override ICreditCard MakeProduct() => new TitaniumCreditCard();
    }

}

客戶端調用：

ICreditCard CreditCardInstance = new PlatinumFactory().CreateCreditCard();
if (CreditCardInstance != null)
{
    Console.WriteLine("CardType : " + CreditCardInstance.GetCardType());
    Console.WriteLine("CreditLimit : " + CreditCardInstance.GetCreditLimit());
    Console.WriteLine("AnnualCharge :" + CreditCardInstance.GetAnnualCharge());
}
else
{
    Console.Write("Invalid Card Type");
}
Console.WriteLine("--------------");
CreditCardInstance = new MoneyBackFactory().CreateCreditCard();
if (CreditCardInstance != null)
{
    Console.WriteLine("CardType : " + CreditCardInstance.GetCardType());
    Console.WriteLine("CreditLimit : " + CreditCardInstance.GetCreditLimit());
    Console.WriteLine("AnnualCharge :" + CreditCardInstance.GetAnnualCharge());
}
else
{
    Console.Write("Invalid Card Type");
}

Console.Read();

參考資料：Factory Method Design Pattern in C#
相比較來說，此示例更貼近實際的業務開發及邏輯，有助於理解工廠模式在業務開發中的應用。