Why does trying to print enum class in c++ give an error?

Question

I want to print u that has km as unit

enum class Unit { km, m, cm };

int main()
{
Unit u = Unit::km; 
std::cout<<u; 
return 0; 
}

Why do i get an error?

error:

error: no match for ‘operator<<’ (operand types are ‘std::ostream {aka std::basic_ostream}’ and ‘Unit’)

**Always** include the verbatim error message(s) when you have questions about errors you receive when compiling code. It should be [included in your question](https://stackoverflow.com/posts/65342305/edit) — WhozCraig, Dec 17 '20 at 14:09
When I run it I get `error: ‘cout’ was not declared in this scope` so I assume it's that? — Dock, Dec 17 '20 at 14:11

score 2 · Accepted Answer · answered Dec 17 '20 at 14:12

2

Your Unit enum is a scoped enumeration, enum class, these types of enums don't allow implicit casting. You'll have to expliticly cast if you want it to work with cout:

std::cout << static_cast<int>(u);

answered Dec 17 '20 at 14:12

Hatted Rooster

35,759
6
62
122

better use `std::underlying_type` (https://en.cppreference.com/w/cpp/types/underlying_type) – 463035818_is_not_an_ai Dec 17 '20 at 14:15
1

@largest_prime_is_463035818 Fair enough, in this example its guaranteed to be `int` though. – Hatted Rooster Dec 17 '20 at 14:17

Why does trying to print enum class in c++ give an error?

1 Answers1