error when declaring an enum to a variable

Question

I have the following syntax:

enum home
{
no,
yes,
}homew;

home homes;

std::string s;
s="no";

homes=s; //is not working. Why?

Were am I wrong?

Don't yell at us, pls (: – Kiril Kirov Jul 27 '11 at 07:49 — Kiril Kirov, Jul 27 '11 at 07:49

score 1 · Accepted Answer · answered Jul 27 '11 at 07:48

1

You are confusing strings with enumerated values.

An enum variable is simply an integer that you can use a literal for at compile time, nothing more than that.

It makes the code more understandable and self-documenting rather than merely using a number literal.

answered Jul 27 '11 at 07:48

Blagovest Buyukliev

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should i have to say homes=0? – sunset Jul 27 '11 at 07:54
@sunset: you would simply say `homes = yes` or `homes = no`. – Blagovest Buyukliev Jul 27 '11 at 07:55

score 1 · Answer 2 · edited May 23 '17 at 12:11

1

This
```
enum home { no, yes, } homew;
```
defines the type home plus a variable homew of that type.
Did you intent that? Why?
The values defined for an enum type are literals, to be used as such:
```
home homes = no;
```
In C++ there's no built-in way to convert between enum value literals and a string representation of them. If you need this, you'll have to cook up your own.

edited May 23 '17 at 12:11

Community

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answered Jul 27 '11 at 07:50

sbi

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i did add homew at the end of enum home because otherwise i had errors. i couldn't say enum home{..}; home homes;. – sunset Jul 27 '11 at 08:02

score 0 · Answer 3 · answered Jul 27 '11 at 07:48

0

enums in C++ are implicitly an int data type. You can't assign string values to enum.

answered Jul 27 '11 at 07:48

Shamim Hafiz - MSFT

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score 0 · Answer 4 · answered Jul 27 '11 at 07:49

0

It doesn't compile because C++ provides no built-in mechanism for converting from std::string to an enum.

answered Jul 27 '11 at 07:49

Oliver Charlesworth

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iammilind · Answer 5 · 2011-07-27T07:55:31.073

0

typeof(home) != typeof(std::string) // types are not equal

Thus, you cannot assign an enum to std::string or otherwise. Implicit conversion between enum and integral types like bool, int etc. is possible however.

Is there a way I can solve my problem as it is?

If possible use std::map.

std::map<std::string, home> myTypes;
myTypes["yes"] = yes;
myTypes["no"] = no;

Now you can do,

homes = myTypes["no"];

edited Jul 27 '11 at 07:55

answered Jul 27 '11 at 07:50

iammilind

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in my case should i have to write homes-=0? THX – sunset Jul 27 '11 at 07:55
@sunset, just click on `std::map`; it's a container class by itself like `std::string`. You can use this container to relate your `string`(key) and `enum`(value). – iammilind Jul 27 '11 at 08:06
You need to `#include `; just refer to the examples in the link I posted. – iammilind Jul 27 '11 at 08:13

Ioan Paul Pirau · Answer 6 · 2011-07-27T08:02:33.270

As others pointed out, enums values are of int type. You could instead write a small function that converts from enum to String like this:

std::string GetStringFromEnum(home iHome)
{
 switch (home)
 {
  case yes: return "yes";
  case no: return "no"; break;
  default: return "here be dragons";
 }
}

and vice-versa:

home GetEnumFromString(std::string iImput)
{
 if (iImput == "yes") return yes;
 return no; //if you extend the enum beyond 2 values, this function will get more complicated
}

and you could modify your code like so:

homes = GetStringFromEnum(no)

the downside for this approach is that if you modify the enum, you must also modify the convert function.

HTH,
JP

error when declaring an enum to a variable

6 Answers6