C++ 使用来自 CRTP 模板-模板库的构造函数 Class

Question

从 curiously recursing template pattern (CRTP) 模板-模板基础 class 继承构造函数的语法是什么？

template<typename T, template<typename> typename U>
struct Base {
    Base(int) { }
};

template<typename T>
struct Derived : public Base<T, Derived> {
    using Base<T, Derived>::Base;
};

int main(int argc, char *argv[]) {
    Derived<double> foo(4);
    return 0;
}

在VS2019中，上述代码导致如下错误：

error C3210: 'Base<double, Derived<double> >': a member using-declaration can only be applied to a base class member
error C3881: can only inherit constructor from direct base

使上述代码工作所需的语法是什么？

Answer 1

这是有效代码，而且 does compile with GCC 9.2。尝试更新版本的编译器或不同的编译器。或联系您的实施者。

在那之前，这里是 does compile with MSVC 现在的解决方法：

template<typename T, template<typename> typename U>
struct Base {
    Base(int) { }
};

template<typename T>
struct Derived;

template<typename T>
using Base_type = Base<T, Derived>;

template<typename T>
struct Derived : public Base_type<T> {
    using Base_type<T>::Base;
};

int main() {
    Derived<double> foo(4);
    return 0;
}

C++ 使用来自 CRTP 模板-模板库的构造函数 Class

C++ Using Constructors from CRTP Template-Template Base Class

c++

visual-studio

templates

using

template-templates