覆盖父常量变量

本文关键字：变量 常量 覆盖 | 更新日期: 2023-09-27 18:21:05

我试图覆盖类常量变量，但我的方法不起作用。

对于以下代码：

// The following line of code should output "DATE: 9/9/2014"
// But it outputs: "DATE: 31/3/2015"
CustomDateChecker.checkUsedByDate();

在以下类别中；如何覆盖变量USED_BY_YEAR、USED_BY_MONTH和USED_BY_DAY？

public class DateChecker
{
    public const uint                   USED_BY_YEAR            = 2015;
    public const uint                   USED_BY_MONTH           = 3;
    public const uint                   USED_BY_DAY             = 31;
    public static bool checkUsedByDate()
    {
        TaskDialog.MessageBox.Show(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
    }
}
public class CustomDateChecker : DateChecker
{
    // Override Date
    public const uint                   USED_BY_YEAR            = 2014;
    public const uint                   USED_BY_MONTH           = 9;
    public const uint                   USED_BY_DAY             = 9;
}

编辑：阅读建议后，我将变量更改为static readonly，而不是const。但不幸的是，同样的问题，日期没有改变。使用static readonly是一种可能的解决方案吗？

public class DateChecker
{
    public static readonly uint                   USED_BY_YEAR            = 2015;
    public static readonly uint                   USED_BY_MONTH           = 3;
    public static readonly uint                   USED_BY_DAY             = 31;
    public static bool checkUsedByDate()
    {
        TaskDialog.MessageBox.Show(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
    }
}
public class CustomDateChecker : DateChecker
{
    // Override Date
    public static new readonly uint                   USED_BY_YEAR            = 2014;
    public static new readonly uint                   USED_BY_MONTH           = 9;
    public static new readonly uint                   USED_BY_DAY             = 9;
}

覆盖父常量变量

public class DateChecker
    {
        public readonly uint USED_BY_YEAR = 2015;
        public readonly uint USED_BY_MONTH = 3;
        public readonly uint USED_BY_DAY = 31;
        public DateChecker()
        {
        }
        public DateChecker(uint d, uint m, uint y)
        {
            this.USED_BY_DAY = d;
            this.USED_BY_MONTH = m;
            this.USED_BY_YEAR = y;
        }
        public bool checkUsedByDate()
        {
            Console.WriteLine(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
            return false;
        }
    }
    public class CustomDateChecker : DateChecker
    {
        // Override Date
        public new const uint USED_BY_YEAR = 2014;
        public new const uint USED_BY_MONTH = 9;
        public new const uint USED_BY_DAY = 9;
        public CustomDateChecker()
            : base(USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR)
        {
        }

    }
    private static void Main(string[] args)
    {
        CustomDateChecker d = new CustomDateChecker();
        d.checkUsedByDate();
    }
  1. 您正试图覆盖字段或成员。重写是与方法/属性关联的功能，而不是与类的字段或成员关联的功能
  2. 这里的另一个问题是，您试图使用静态方法来获得多态行为，但这不会成功。静态方法与类关联，而不是与类的实例关联。因此，静态方法不能与针对它的虚拟/重写限定符一起使用。为此，应该使用实例方法/非静态方法或属性

  3. 看看下面的例子是否有帮助。

            public class DateChecker
        {
            public virtual uint USED_BY_YEAR { get; set; }
            public virtual uint USED_BY_MONTH { get; set; }
            public virtual uint USED_BY_DAY { get; set; }
            public DateChecker()
            {
                USED_BY_YEAR = 2015;
                USED_BY_MONTH = 3;
                USED_BY_DAY = 31;
            }
            public virtual void checkUsedByDate()
            {
                Console.Write(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
            }
        }
     public class CustomDateChecker : DateChecker
    {
        public override uint USED_BY_DAY
        {
            get
            {
                return 9;
            }
            set
            {
                base.USED_BY_DAY = value;
            }
        }
        public override uint USED_BY_MONTH
        {
            get
            {
                return 9;
            }
            set
            {
                base.USED_BY_MONTH = value;
            }
        }
        public override uint USED_BY_YEAR
        {
            get
            {
                return 2014;
            }
            set
            {
                base.USED_BY_YEAR = value;
            }
        }        
    }
    class Program
    {        
        static void Main(string[] args)
        {
            new CustomDateChecker().checkUsedByDate();
        }
    }
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