resolve enum class variable name

June 3, 2022

Consider I’ve got the followin enum class:

enum class TestEnum
{
   None = 0,
   Foo,
   Bar
};

I’d like to specify ostream operator ( << ) for this enum class so I could write:

std::cout << "This is " << TestEnum::Foo;

and get following output This is Foo.
My question is:
Is there any place where enum "name specifiers" are stored? (i.e. for enum class TestEnum it is None, Foo and Bar) So I could write a function ( or at best function template ) that specifies ostream operator for this TestEnum like:

std::ostream& operator<< ( std::ostream& os, TestEnum aEnum )
{
   return std::string( aEnum.name() );
}

So far I did it this way:

std::ostream& operator<< ( std::ostream& os, TestEnum aEnum )
{
   switch( aEnum )
   {
   case TestEnum::Foo:
       os << "Foo";
       break;
   case TestEnum::Bar:
       os << "Bar"
       break;
   }
   return os;
}

I’ve seen some solutions using boost library but I would prefer not using it this time.

>Solution :

Is there any place where enum "name specifiers" are stored?

No, but one option is to use std::map<TestEnum, std::string> as shown below:

enum class TestEnum
{
   None = 0,
   Foo,
   Bar
};
std::map<TestEnum,std::string> myMap{{TestEnum::None, "None"}, 
                                     {TestEnum::Foo, "Foo"}, 
                                     {TestEnum::Bar, "Bar"}};
    
std::ostream& operator<< ( std::ostream& os, TestEnum aEnum )
{
   os << myMap.at(aEnum);
   return os;
}
int main()
{
    std::cout << "This is " << TestEnum::Foo; //prints This is Foo 
    std::cout << "This is " << TestEnum::Bar; //prints This is Bar

    return 0;
}

Demo