如何确保CRTP提供错误的超类？ [英] How to secure CRTP against providing wrong superclass?

问题描述

在好奇的重复模板模式中，我们写入

template <class Derived>
class Base {
};

class Derived : public Base<Derived> {
};

这将是一个很好的方法，使代码健壮另一个复制粘贴遗漏， snippet抛出编译时错误：

What would be a good way to make the code robust another copy-paste omissions, so that the following snippet throws a compile-time error:

class AnotherDerived : public Base<Derived> {
};

我使用Visual C ++ 2013。

I'm using Visual C++ 2013.

推荐答案

使基础的析构函数私有，然后使派生 的朋友 ：

Make Base's destructor private, and then make Derived a friend of Base<Derived>:

template <class Derived>
class Base {
    private: ~Base() = default;
    friend Derived;
};

class Derived : public Base<Derived> {
};

这实际上不会做

class AnotherDerived : public Base<Derived> {
};

非法，但任何尝试实际构造 AnotherDerived 将失败。

illegal, but any attempt to actually construct an AnotherDerived will fail.

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