可能的话，只向基类公开构造函数

本文关键字：基类 构造函数 | 更新日期: 2023-09-27 18:10:01

public class Base<S>
{
    public static Derived<S, T> Create<T>()
    {
        return new Derived<S, T>(); //if not public, I wont get it here.
    }
}
public class Derived<S, T> : Base<S>
{
    public Derived() //the problem, dont want it public
    {
    }
}

这是我得到的基本结构。

要求:

1)我不希望Derived<,>的实例被构造调用Derived<,>类，无论是通过构造函数或静态方法。我希望它只通过Base<>创建。所以这是:

public class Derived<S, T> : Base<S>
{
    Derived()
    {
    }
    public static Derived<S, T> Create()
    {
        return new Derived<S, T>();
    }
}

2) Derived<,>类本身必须是公共的(这意味着我不能在Base<>内部私有嵌套Derived<,>)。只有这样，我才能从Base<>中的静态Create方法返回Derived<,>。

有可能吗?

可能的话，只向基类公开构造函数

您可以使派生类的构造函数internal如

所示
public class Base<S>
{
    public static Derived<S, T> Create<T>()  // visible externally
    {
        return new Derived<S, T>(); 
    }
}
public class Derived<S, T> : Base<S>
{
    internal Derived() // not visible outside the current assembly
    {
    }
}

反思!

void Main()
{
    Derived dr = Base.GetDerived<Derived>();
}
public class Base
{
    public int ID { get; set; }
    public Base()
    {
    }
    public static T GetDerived<T>() where T : Base
    {
        T toReturn = (T)typeof(T).GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance, null, Type.EmptyTypes, null).Invoke(null);
        return toReturn;
    }
}
public class Derived : Base
{
    private Derived()
    {
    }
}

我将声明一个公共接口，并在Base中实现私有:

public class Base<S>
{
    public static IFoo<S, T> Create<T>()
    {
        return new Derived<T>(); //if not public, I wont get it here.
    }
    // Only generic in T, as we can use S from the containing class
    private class Derived<T> : Base<S>, IFoo<S, T>
    {
        public Derived()
        {
            ...
        }
    }
}
public interface IFoo<S, T>
{
    // Whatever members you want
}

我这样实现了我的要求:

public abstract class Base<S>
{
    public static Derived<S, T> Create<T>() 
    {
        return new ReallyDerived<S, T>(); 
    }

    class ReallyDerived<T> : Derived<S, T>
    {
        public ReallyDerived()
        {
        }
    }
}
public abstract class Derived<S, T> : Base<S>
{
}

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