c++11的动态类型

c++17引入了any 和 variant，可以将任意数据类型统一用any或variant类型表示，在开发中还是能够带来很多便利的。在c++11版本中，可以用下面这个例子，仿照实现一个Any类型。(参考：https://mp.weixin.qq.com/s/26ODHzsI9OZedKE6GoJZMg)

#include 
#include 
#include 
#include 
 
class UserData{
public:
	UserData(){}
	std::string operator()()
	{
        return m_name;
	}
private:
	std::string m_name="world";
};

class Any
{
public:
    Any() noexcept : content(nullptr) {}
	template
	Any(const T& val) noexcept : content(new Holder(val)) {}
	Any(const Any& other) noexcept : content(other.content ? other.content->Copy() : nullptr) {}
	Any(Any&& other) noexcept :content(std::move(other.content)) {}
	Any& operator=(const Any& other)
	{
		if (this == &other)
			return *this;
		content.reset(other.content ? other.content->Copy() : nullptr);
		return *this;
	}
	template
	T& get() const
	{
		if (content.get() == nullptr)
		{
			throw std::exception_ptr();
		}
		if (typeid(T).hash_code() != content->TypeID())
		{
			throw std::bad_cast();
		}
		return static_cast*>(content.get())->value;
	}
	std::string TypeName() const
	{
		if (content)
			return content->TypeName();
		return "";
	}
	size_t TypeID()
	{
		if (content)
			return content->TypeID();
		return 0;
	}
private:
	struct Base {
		virtual ~Base() {}
		virtual Base* Copy() const = 0;
		virtual size_t TypeID() const = 0;
		virtual const char* TypeName() const = 0;
	};
	template
	struct Holder :public Base
	{
		Holder() = delete;
		Holder(const T& val) : value(val), typid(typeid(T).hash_code()), typname(typeid(T).name()) {}
		~Holder() {}
		Base* Copy() const override { return new Holder(value); }
		size_t TypeID() const override { return typid; }
		const char* TypeName() const override { return typname; }
		T value;
		size_t typid;
		const char* typname;
	};
	std::unique_ptr content;
};

int main()
{
    int iVal = 10;
    Any param = iVal;
	int& iv = param.get();
	iv = 100;
    std::cout<