C++ 如何判断一个类型是STL容器的类型

一、定义是否是容器类型

#include <IOStream>

#include <string>
#include <type_traits>   // std::enable_if 
#include <utility>  // std::pair
#include <functional>

#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>

// 默认类型为false
template<typename T,typename... Types>
struct IsContainerType
{
	static const bool value = false;
};

// Vector类型为true
template<typename T,typename... Types>
struct IsContainerType<std::vector<T, Types...>>
{
	static const bool value = true;
};

// deque类型
template<typename T,typename... Types>
struct IsContainerType<std::deque<T, Types...>>
{
	static const bool value = true;
};

// set类型
template<typename T,typename... Types>
struct IsContainerType<std::set<T, Types...>>
{
	static const bool value = true;
};

// multiset类型
template<typename T,typename... Types>
struct IsContainerType<std::multiset<T, Types...>>
{
	static const bool value = true;
};

// map类型
template<typename K,typename V,typename... Types>
struct IsContainerType<std::map<K, V, Types...>>
{
	static const bool value = true;
};

// multimap类型
template<typename K,typename V,typename... Types>
struct IsContainerType<std::multimap<K, V, Types...>>
{
	static const bool value = true;
};

// 定义获取容器类型的模板
template<typename T,typename... Types>
constexpr bool is_container = IsContainerType<T, Types...>::value;

二、测试是否是容器类型

template<typename T>
bool TestContainer(std::string name, const T& cntr)
{
	if (is_container<T>)
	{
		std::cout << "Yes, " << name << " is a container!n";
		return true;
	}
	else
	{
		std::cout << "No, " << name << " is not a container!n";
		return false;
	}
}

测试实例

	std::vector<int> v{ 1,2,3,4,5,6,7,8,9,10 };
	std::set<int> s{ 1,2,3,4,5 };
	std::map<std::string, int> m{ {"Trump",23},{"Moon",30},{"Han shuang",28},{"Liu sai",23} };
	std::string msg{ "hello container!" };

// 测试是否属于容器类型
if (is_container<decltype(v)>)
	{
		std::cout << "Yes,containern";
	}
	else
	{
		std::cout << "No, not containern";
	}

	if (is_container<decltype(m)>)
	{
		std::cout << "Yes,containern";
	}
	else
	{
		std::cout << "No, not containern";
	}

  TestContainer("v", v);
	TestContainer("s", s);
	TestContainer("m", m);
	TestContainer("msg", msg);

	int a = 6;
	TestContainer("a", a);

// 测试结果
Yes,container
Yes,container
Yes, v is a container!
Yes, s is a container!
Yes, m is a container!
No, msg is not a container!
No, a is not a container!