Question

假设我有以下课程：

public class Gender
{
    public readonly string Name { get; set;}
    public readonly char Abbreviation { get; set;} 
    public readonly string ChildName { get; set;}
    public readonly int Number { get; set;}

    public static Gender Male = new Gender { Name = "Male", Abbreviation = 'M', Number = 1, ChildName = "Boy" };
    public static Gender Female = new Gender { Name = "Female", Abbreviation = 'F', Number = 2, ChildName = "Girl" };
    public static Gender Unknown = new Gender { Name = "Unknown", Abbreviation = 'U', Number = 0, ChildName = "Unknown" };
}

除了

之外，我怎么能通过任何其他方式将Gender类实例化为非法

Gender MyGender = Gender.Male

从而制作

Gender Spaghetti = new Gender{Name = "Spaghetti", Abbreviation = 'S', Number = 123, ChildName = "Angel Hair" }

在编译时抛出错误？

Answer 1

将private构造函数添加到Gender类：

public class Gender
{
    public readonly string Name { get; set;}
    public readonly char Abbreviation { get; set;} 
    public readonly string ChildName { get; set;}
    public readonly int Number { get; set;}

    private Gender()
    {
    }

    public static Gender Male = new Gender { Name = "Male", Abbreviation = 'M', Number = 1, ChildName = "Boy" };
    public static Gender Female = new Gender { Name = "Female", Abbreviation = 'F', Number = 2, ChildName = "Girl" };
    public static Gender Unknown = new Gender { Name = "Unknown", Abbreviation = 'U', Number = 0, ChildName = "Unknown" };
}

您也可以向readonly / Male / Female声明添加Unknown，以便无法使用以下代码：

Gender.Male = Gender.Female;

Answer 2

给它一个私有构造函数：

public class Gender
{
    // ...

    private Gender() {  }
}

通常，如果没有定义构造函数，则编译器会创建一个没有参数的“默认构造函数”。但如果你定义一个，那就没有默认值。如果那个是私人的，那个班级之外的任何东西都不能称之为。因此除了Gender本身之外，没有任何东西可以构建Gender的实例。

Answer 3

使构造函数成为私有的。这就是它在SingleTon模式中的使用方式。

可以仅通过静态属性实例化子类

3 个答案: