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

< cpp‎ | types‎ | type info

bool operator==( const type_info& rhs ) const; |  | (C++11 前)
bool operator==( const type_info& rhs ) const noexcept; |  | (C++11 起) (C++23 前)
constexpr bool operator==( const type_info& rhs ) const noexcept; |  | (C++23 起)
bool operator!=( const type_info& rhs ) const; |  | (C++11 前)
bool operator!=( const type_info& rhs ) const noexcept; |  | (C++11 起) (C++20 前)

检查对象是否指代相同类型。

`!=` 运算符从 `operator==` 合成。 | (C++20 起)

### 参数

rhs | - | 要比较的另一个类型信息对象

### 返回值

若比较关系成立则为 true ，否则为 false

### 示例

    #include <iostream>
    #include <typeinfo>
    #include <string>
    #include <utility>

    class person
    {
      public:

       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 somefunc(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()
    {
       somefunc(employee{"Paul","Economics"});
       somefunc(person{"Kate"});

    #  if defined(__cpp_lib_constexpr_typeinfo) // C++23
       if constexpr (typeid(employee) != typeid(person)) {
          std::cout << "class `employee` != class `person`\n";
       }
    #  endif
    }

输出：

    Paul is an employee who works in Economics
    Kate is not an employee

### 参阅

before | 检查在实现定义的顺序中，被指代类型是否在另一个 `type_info` 对象之前，即对被指代类型排序 (公开成员函数)