enum as argument returning string

Question

My current program uses 3 different enums:

enum ThingEnum{
    Thing1 = 0,
    Thing2 = 1,
    Thing3 = 2,
    OtherThing = 3
};
enum ReturnEnum {
    Success = 4,// the method did what it is supposed to
    Error1 = 5,// an error occured
    Error2 = 6,// an error occured
    Error3 = 7,// an error occured
    Error4 = 8,// a fatal error occured program must terminate
    Pointer = 9// the method may need to be called again
};
enum TypeEnum {
    Type1 = 10,
    Type2 = 11,
    Type3 = 12,
    Type4 = 13,
    OtherType = 14
};

What I want to do is create a global function that takes an enum and returns a string (as the value of an enum is really just a specialized variable name that always has a value). Is it possible to create a function that takes a generic enum? e.g.

string enumToString (enum _enum){}

or would I have to make a function for each different enum? Just a possible thought I did some reading, and some compilers allow for a Enum to resolve to an int so could I pass the enum as an int and then work with it?

So what you want to do is convert an enum value to a string? Maybe you should revise the question title... — tenfour
– tenfour, Commented Feb 2, 2012 at 11:41
as the value of an enum is really just a specialized variable name that always has a value whut — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Feb 2, 2012 at 11:52
@Lightness when the compiler reads enum Ex{this, thisTo}; it will generate values for them (unless they are set to specifics), but to access them you need to use the name representing that value as kind of like using a resolution operator to get to an exact method in a class. as literature on enums will state "an Enum will resolve to a specific value (an int address), but even if that value is known the reverse conversion will never resolve" — gardian06
– gardian06, Commented Feb 2, 2012 at 12:18
@gardian06: Yes, I know what enums are, thanks. I was wondering what on earth the quoted passage was supposed to mean. — Lightness Races in Orbit
– Lightness Races in Orbit, Commented Feb 2, 2012 at 14:01
@LightnessRacesinOrbit it means that you can use an enum the same that in C you could use #define CONST_THING = 0x0A and every time you use CONST_THING it will always resolve to that value. the same way that enum Ex{this, thisTo} every time you use thisTo it will always resolve to the value assigned to it (assuming scope) hens Ex is a specialized variable, and thisTo is its value. yes the better statement probably should have been "as an enum is really just a specialized variable that has preset known values" — gardian06
– gardian06, Commented Feb 3, 2012 at 0:56

Sergey Vyacheslavovich Brunov · Accepted Answer · 2012-02-02 12:05:24Z

2

There are two options of "ToString-like" function implementation:

Implement a simple static switch-case function.

Code:

std::string ThingEnumToString(ThingEnum thing)
{
    switch (thing) {
    case Thing1:
        return std::string("Thing1");
    case Thing2:    
        return std::string("Thing2");
    case Thing3:
        return std::string("Thing3");        
    case OtherThing:
        return std::string("OtherThing");
    default:
        throw std::invalid_argument("thing");
        break;
    }
}

Implement a static function with a dictionary lookup.

Code:

typedef std::map<ThingEnum, std::string> ThingsMap;

static ThingsMap GetThingsMap()
{
    ThingsMap things_map;
    things_map.insert(ThingsMap::value_type(Thing1, std::string("Thing1")));
    things_map.insert(ThingsMap::value_type(Thing2, std::string("Thing2")));
    things_map.insert(ThingsMap::value_type(Thing3, std::string("Thing3")));
    things_map.insert(ThingsMap::value_type(OtherThing, std::string("OtherThing")));
    return things_map;
}

static std::string ThingEnumToString(ThingEnum thing)
{
    static const ThingsMap things(GetThingsMap());
    ThingsMap::const_iterator it = things.find(thing);
    if (it != things.end()) {
        return it->second;
    } else {
        throw std::invalid_argument("thing");
    }
}

answered Feb 2, 2012 at 12:05

Sergey Vyacheslavovich Brunov

18.2k7 gold badges53 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Sergey Vyacheslavovich Brunov Over a year ago

Personally, I choose the first one when there a few enumeration constants. On the contrary, the second one is actual when there is a lot of enumeration constants.

Tom Tanner · Accepted Answer · 2012-02-02 13:01:51Z

2

This is one of those cases where I'd advocate the use of macros to make your code more intelligible / maintainable (and remove at least one source of errors)

Thus

  #define TOSTRING(name) case name: return #name
  switch (val)
  {
      TOSTRING(Thing1);
      TOSTRING(Thing2);
      default:
         //bad things happened.
   }

answered Feb 2, 2012 at 13:01

Tom Tanner

9,3703 gold badges37 silver badges61 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 12:27:29Z

1

No, enums have no implicit base class.

You can use templates, or function overloading. But, yes, you're going to have to do it by hand.

There are some tricks for enum→string "conversion" listed here.

edited May 23, 2017 at 12:27

CommunityBot

11 silver badge

answered Feb 2, 2012 at 11:53

Lightness Races in Orbit

387k77 gold badges670 silver badges1.1k bronze badges

Comments

Luchian Grigore · Accepted Answer · 2012-02-02 11:53:24Z

0

enum names only make sense before compilation. I don't think there's a portable or standard-defined way of doing this in a clean fashion.

You could do it as follows:

std::string getName(ThingEnum x)
{
   switch (x)
   {
   case Thing1:
      return "Thing1";
   case Thing2:
      return "Thing2";
   //....
   }
}

edited Feb 2, 2012 at 11:53

answered Feb 2, 2012 at 11:47

Luchian Grigore

260k68 gold badges465 silver badges634 bronze badges

3 Comments

gardian06 Over a year ago

basically if I can get the enum into the function then I can basically do like a case switch to return the right string. I don't necessarily want to have it return its own name, but at least have a logic check done on it.

Luchian Grigore Over a year ago

@gardian06 yes, like in my edit, but it's not generic(which wouldn't make sense anyway) and you have to hardcode a lot of stuff. Why would you need this anyway?

gardian06 Over a year ago

to generate log messages. because I will have to be integrating stuff on top of these, and "method returned: 6" is not as meaningful as "method returned: Error2" for debugging.

Collectives™ on Stack Overflow

enum as argument returning string

4 Answers 4

1 Comment

Comments

Comments

3 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related