1

有没有办法在它们之间组合(或合并、聚合)POD?一种直观的解决方案:

struct Base1 { int i; };
struct Base2 { char c; };

struct Derived : Base1, Base2 {};

// in a more generalized way
// template <class... Ts> struct Aggregate : Ts... {};

除了,我们失去了一些东西:

int main()
{
    Derived d {42, 'c'}; // OK
    auto [i, c] = d; // Error
    static_assert(std::is_standard_layout_v<Derived>); // Error
}

我看到我们最终可能会在合并的基类之间出现一些歧义和冲突。但是将 POD 合并为一个会非常好。我试图达到的结果:

struct Expected { int i; char c; }; // I want Derived to behave exactly like this

我在反思的领域吗?我应该最终使用宏吗?

4

1 回答 1

1

要是我们

不关心派生结构是否是 POD

,任务非常简单Boost.PFR- 只需将您的 POD 转换为元组并将它们连接起来:

template<typename... Ts> using Merge = decltype(std::tuple_cat(
    boost::pfr::structure_to_tuple(std::declval<Ts>())...
));

一个简单的测试:

int main() {
    struct Base1 { int i, j; };
    struct Base2 { char c; };
    using Expected = Merge<Base1, Base2>;
    static_assert(std::is_same_v<Expected, std::tuple<int, int, char>>);
    Expected expected{42, 1337, 'c'};
    auto&& [i, j, c] = expected;
}
于 2021-10-18T22:00:57.407 回答