Why is enum class preferred over plain enum?

Question

I heard a few people recommending to use enum classes in C++ because of their type safety.

But what does that really mean?

Answer 1

It's worth noting, on top of these other answers, that C++20 solves one of the problems that enum class has: verbosity. Imagining a hypothetical enum class, Color.

void foo(Color c)
  switch (c) {
    case Color::Red: ...;
    case Color::Green: ...;
    case Color::Blue: ...;
    // etc
  }
}

This is verbose compared to the plain enum variation, where the names are in the global scope and therefore don't need to be prefixed with Color::.

However, in C++20 we can use using enum to introduce all of the names in an enum to the current scope, solving the problem.

void foo(Color c)
  using enum Color;
  switch (c) {
    case Red: ...;
    case Green: ...;
    case Blue: ...;
    // etc
  }
}

So now, there is no reason not to use enum class.