table of contents
std::type_info::operator==,std::type_info::operator!=(3) | C++ Standard Libary | std::type_info::operator==,std::type_info::operator!=(3) |
NAME¶
std::type_info::operator==,std::type_info::operator!= - std::type_info::operator==,std::type_info::operator!=
Synopsis¶
bool operator==( const type_info& rhs ) const; (until
C++11)
bool operator==( const type_info& rhs ) const noexcept; (since
C++11)
(until C++23)
constexpr bool operator==( const type_info& rhs ) const noexcept; (since
C++23)
bool operator!=( const type_info& rhs ) const; (until C++11)
bool operator!=( const type_info& rhs ) const noexcept; (since
C++11)
(until C++20)
Checks if the objects refer to the same types.
The != operator is synthesized from operator==. (since C++20)
Parameters¶
rhs - another type information object to compare to
Return value¶
true if the comparison operation holds true, false otherwise
Notes¶
Feature-test macro: __cpp_lib_constexpr_typeinfo
Example¶
// Run this code
#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 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 constexpr (typeid(employee) != typeid(person)) // C++23
{
std::cout << "class `employee` != class `person`\n";
}
}
Output:¶
Paul is an employee who works in Economics
Kate is not an employee
class `employee` != class `person`
See also¶
checks whether the referred type precedes referred type of
another type_info
before object in the implementation defined order, i.e. orders the referred
types
(public member function)
2022.07.31 | http://cppreference.com |