How to access an C++11 enum class from another file?

Question

I have a header file that will eventually include more than one enum class. However, when I include the header file in another file and try to use the enum class, my program will not compile. For example:

enums.h:

#ifndef ENUMS_H
#define ENUMS_H

enum class TokenType : char
{
     IDEN,
     STRING,
     SEMICO
};

#endif

and main.cpp:

#include <iostream>
#include "enums.h"

int main()
{
     char token = TokenType::STRING; //Does not compile!
}

However, when I use a regular enum, it compiles correctly:

enums.h:

#ifndef ENUMS_H
#define ENUMS_H

enum TokenType : char
{
     IDEN,
     STRING,
     SEMICO
}

#endif

and main.cpp:

#include <iostream>
#include "enums.h"

int main()
{
     char token = STRING; //This does compile!
}

Does anyone know how to do this correctly? I've searched a lot and came up with nothing.

`TokenType` is *not* a `char` even if its underlying type is. It is its own type and does not implicitly convert. You need to use a variable of the correct (`TokenType`) type or use an explicit cast. This, by the way, is a *good* thing compared to old `enum`s. — Jesper Juhl, Feb 16 '19 at 10:02

score 3 · Answer 1 · answered Feb 16 '19 at 09:58

enum class do not participate in implicit conversion whereas unscoped enums do. Thus,

int main()
{
     TokenType token = TokenType::STRING;
}

will compile.

You can see How to automatically convert strongly typed enum into int? how to otherwise convert an enum class to some other value.

score 0 · Answer 2 · answered Feb 16 '19 at 10:04

0

Enum is strongly type and you cannot assign enum to an int or char without casting it. You can try:

int main() 
{
  char token = (char)TokenType::STRING; 
}

answered Feb 16 '19 at 10:04

Patryk kowalski

313
2
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18

Prefer C++style casts over C-style casts if you *must* use a cast (always prefer *not* to). In this case `static_cast`. – Jesper Juhl Feb 16 '19 at 10:08

How to access an C++11 enum class from another file?

2 Answers2