std::type_index
Defined in header <typeindex> | | |
|---|---|---|
class type_index; | | (since C++11) |
大type_index类的包装器类。std::type_info对象，可用作关联和无序关联容器中的索引。与...的关系type_info对象是通过指针维护的。type_index是CopyConstructible和CopyAssignable...
成员函数
(constructor) | constructs the object (public member function) |
|---|---|
(destructor) (implicitly declared) | destroys the type_index object (public member function) |
operator= (implicitly declared) | assigns a type_index object (public member function) |
operator==operator!=operator<operator<=operator>operator>= | compares the underlying std::type_info objects (public member function) |
hash_code | returns hashed code (public member function) |
name | returns implementation defined name of the type, associated with underlying type_info object (public member function) |
帮助者类
std::hash<std::type_index> (C++11) | hash support for std::type_index (class template specialization) |
|---|
例
下面的程序是一个有效的类型值映射的示例。
二次
#include <iostream>
#include <typeinfo>
#include <typeindex>
#include <unordered_map>
#include <string>
#include <memory>
struct A {
virtual ~A() {}
};
struct B : A {};
struct C : A {};
int main()
{
std::unordered_map<std::type_index, std::string> type_names;
type_names[std::type_index(typeid(int))] = "int";
type_names[std::type_index(typeid(double))] = "double";
type_names[std::type_index(typeid(A))] = "A";
type_names[std::type_index(typeid(B))] = "B";
type_names[std::type_index(typeid(C))] = "C";
int i;
double d;
A a;
// note that we're storing pointer to type A
std::unique_ptr<A> b(new B);
std::unique_ptr<A> c(new C);
std::cout << "i is " << type_names[std::type_index(typeid(i))] << '\n';
std::cout << "d is " << type_names[std::type_index(typeid(d))] << '\n';
std::cout << "a is " << type_names[std::type_index(typeid(a))] << '\n';
std::cout << "b is " << type_names[std::type_index(typeid(*b))] << '\n';
std::cout << "c is " << type_names[std::type_index(typeid(*c))] << '\n';
}二次
产出：
二次
i is int
d is double
a is A
b is B
c is C二次
另见
type_info | contains some type's information, generated by the implementation. This is the class returned by the typeid operator. (class) |
|---|
© cppreference.com在CreativeCommonsAttribution下授权-ShareAlike未移植许可v3.0。
本文档系腾讯云开发者社区成员共同维护，如有问题请联系 cloudcommunity@tencent.com
