有条件的非此即彼的类型约束 [英] Conditional either-or on type constraint

问题描述

是否有可能有一种类型的约束是或两种类型的，而不是一个和的。一个和是通过将两种类型之间逗号来完成。但对于一个或

Is it possible to have a type constraint that is an "or" of two types instead of an "and". An "and" is accomplished by putting a comma between the two types. But what about an "or"?

class Type1<T, U>
{
    public static Type1<T, U> New<V>( V v )
        where V : T, U
    {
        return new Type1<T, U>();
    }
}

因此，在上述的例子中，参数传递到新（）必须是一个T和一个U.但我想这是不是一件T 或 U形。

推荐答案

有没有办法表达你描述的方式或约束。然而，你可以通过让两个重载其中一个接受 U 和其他效仿这一 T 。那么这两个可以喂到它处理 T 或 U

There is no way to express the "or" constraint in the manner you described. However you can emulate this by having two overloads one which accepts U and the other T. These two can then feed into a common function which handles T or U

class Type1<T, U> {
  public static Type1<T, U> New(U p) {
    return NewCore(p);
  }

  public static Type1<T, U> New(T p) {
    return NewCore(p);
  }

  private static Type1<T, U> New(object o) {  
    ...
  }
}

不太清楚你想要的 T 或 U 参数做什么，虽然。也许你可以详细一点

Not quite sure what you'd want to do with the T or U parameter though. Perhaps you could elaborate a bit

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