[英]Partial template specialization for constructor
I need a class which looks like this:我需要一个看起来像这样的 class:
template<typename T, class S, size_t C>
class myClass
{
public:
myClass(); // Ctor
/*
*/
private:
S myData;
}
Where T is type of stored data, S is a container type and C is it's size.其中 T 是存储数据的类型,S 是容器类型,C 是它的大小。 Methods won't depend on a container type, but I still need to properly initialize S. For example, let S be std::vector
, I tried:方法不依赖于容器类型,但我仍然需要正确初始化 S。例如,让 S 为std::vector
,我试过:
template<typename T, size_t C>
myClass<T, std::vector<T>, C>::myClass()
{
}
But I get E0040 expected identifier
error.但我收到E0040 expected identifier
错误。
You cannot partial specialize a method, you could partial specialize the whole class, but require some duplication.您不能部分专门化一个方法,您可以部分专门化整个 class,但需要一些重复。
As you can use C++17, you might tweak the implementation instead:由于您可以使用 C++17,因此您可以调整实现:
template<typename T, class S, size_t C>
myClass<T, S, C>::myClass()
{
if constexpr (std::is_same_v<S, std::vector<T>>) {
// special case
} else {
// regular case
}
}
tag dipatching in another option (pre-C++17) which has the advantage to allow member initializer list:在另一个选项(C++ 17 之前)中标记 dipatching,其优点是允许成员初始化器列表:
template <typename T> struct tag{};
template <typename T, class S, size_t C>
class myClass
{
private:
myClass(tag<std::vector<T>>) : myData(/*special case */) {/* special case */}
template <typename U>
myClass(tag<U>) : myData(/*regular case */) {/* regular case */}
public:
myClass() : myClass(tag<S>{}) {}
private:
S myData;
};
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