使用泛型键入安全枚举模式实现

Question

如何在泛型类上实现类型安全枚举模式？我们假设它是按照这些方式实现的

public class KnownSetting<T>
{
    public readonly static KnownSetting<String> Name = new KnownSetting<String>("name", "Default Name", t => t);
    public readonly static KnownSetting<int> Size = new KnownSetting<String>("size", "25", t => Converter.ToInt32);

    public String Key { get; set; }
    public T DefaultValue { get; set; }
    public Func<String, T> Converter { get; set; }

    private KnownSetting(String key, T defaultValue, Func<String, T> converter)
    {
        Key = key;
        DefaultValue = defaultValue;
        Converter = converter;
    }
}

由于构造函数保持私有,因此模式的实现是正确的,但是在使用此构造时,它看起来是错误的:

public static class Program
{
    public static void main()
    {
        var x = KnownSetting<?>.Name;
    }
}

然后一个选项是将它分成两个,KnownSetting容器类和Setting实现,但是然后构造函数的范围不能是私有的,以便从容器中实例化.

如何实现这种模式,以便它的泛型方面隐藏在最终用户之外,但仍保持强类型？是否有更合适的模式,还是有更好的方法来实现它？

更新 我添加了第二个示例,以说明我确实希望设置的类型是通用的.

Answer 1

在使用另一种类型的基类型中创建一个辅助方法，并创建一个已知的设置类。您需要 Create 方法，因为基本构造函数是Setting(string, object, Func)。这也是我引入另一个通用变量（U）的原因：

public class KnownSetting : Setting<object>
{
    private KnownSetting(string key, object defaultValue, Func<string, object> converter) : base(key, defaultValue, converter) { }

    public readonly static Setting<string> Name = Create<string>("name", "Default Name", t => t);
    public readonly static Setting<int> Size = Create<int>("size", 25, t => Convert.ToInt32(t));
}

public class Setting<T>
{
    public string Key { get; set; }
    public T DefaultValue { get; set; }
    public Func<string, T> Converter { get; set; }

    protected static Setting<U> Create<U>(string key, U defaultValue, Func<string, U> converter)
    {
        return new Setting<U>(key, defaultValue, converter);
    }

    protected Setting(string key, T defaultValue, Func<string, T> converter)
    {
        Key = key;
        DefaultValue = defaultValue;
        Converter = converter;
    }
}
public static class Program
{
    static void Main(string[] args)
    {
        var x = KnownSetting.Name;
    }
}