如何测试类B是否派生自类A？ [英] How to test whether class B is derived from class A?

问题描述

更具体地说，假设我有一个具有参数 A 和 B 的类模板，有一个编译器错误（当模板被实例化时）如果B不是从A派生的。

More specifically, let's say I have a class template with parameters A and B, and I would like to have a compiler error (when the template is being instantiated) if B is not derived from A.

template<class A, class B>
class Foo
{
    // static_assert(B is derived from A)
};

推荐答案

它很简单我会再次发布的解决方案：

This has been asked so very many times before, but it's so simple I'll post the solution again:

~Foo()
{
    A* p = (B*)0; // B is required to be a subtype of A
}

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