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std::type_info:: operator==, std::type_info:: operator!=

From cppreference.net
C++
Utilities library
Type support
std::type_info
Member functions
type_info::operator== type_info::operator!=
(until C++20)
(C++11)
bool operator == ( const type_info & rhs ) const ;
(1) (自 C++11 起为 noexcept)
(自 C++23 起为 constexpr)
bool operator ! = ( const type_info & rhs ) const ;
(2) (自 C++11 起为 noexcept)
(C++20 前)

检查对象是否引用相同类型。

!= 运算符由 operator== 合成生成 。

(since C++20)

目录

参数

rhs - 要与之比较的另一个类型信息对象

返回值

true 表示比较操作成立， false 表示不成立。

注释

功能测试 宏 值 标准 功能
__cpp_lib_constexpr_typeinfo 202106L (C++23) std::type_info::operator== 的常量表达式支持

示例

运行此代码 
#include <iostream>
#include <string>
#include <typeinfo>
#include <utility>
class person
{
public:
    explicit person(std::string n) : name_(std::move(n)) {}
    virtual const std::string& name() const { return name_; }
private:
    std::string name_;
};
class employee : public person
{
public:
    employee(std::string n, std::string p)
        : person(std::move(n)), profession_(std::move(p)) {}
    const std::string& profession() const { return profession_; }
private:
    std::string profession_;
};
void print_info(const person& p)
{
    if (typeid(person) == typeid(p))
        std::cout << p.name() << " is not an employee\n";
    else if (typeid(employee) == typeid(p))
    {
        std::cout << p.name() << " is an employee ";
        auto& emp = dynamic_cast<const employee&>(p);
        std::cout << "who works in " << emp.profession() << '\n';
    }
}
int main()
{
    print_info(employee{"Paul","Economics"});
    print_info(person{"Kate"});
#if __cpp_lib_constexpr_typeinfo
    if constexpr (typeid(employee) != typeid(person)) // C++23
        std::cout << "class `employee` != class `person`\n";
#endif
}

可能的输出： 

Paul is an employee who works in Economics
Kate is not an employee
class `employee` != class `person`

参见

检查所引用类型在实现定义的顺序中是否先于另一个 type_info
对象所引用的类型，即对引用类型进行排序
(公开成员函数)