Question

The struct is as follows:

struct padData 
{
    enum buttonsAndAxes
    {
        select,
        start,
        ps
    };
};

The object of the struct:

padData        pad;

I am accessing this enum as follows:

printf ("\n%d", pad.buttonsAndAxes[0]);

Error:

error: invalid use of ‘enum padData::buttonsAndAxes’

Then, I tried:

printf ("\n%d", pad::buttonsAndAxes[0]);

Error:

error: ‘pad’ is not a class or namespace

Now what? Please guide.

Compiler: gcc version 4.5.0

EDIT 1:____________________________________

printf ("\nemit: %d", padData::(select)0);

results in:

error: expected unqualified-id before ‘(’ token

My aim is to fetch the word “select” through its value 0. How to achieve that? Also, is the word “select” a string?

Answer 1

The enum values become names in the scope of the class. So you would use padData::select from outside the class, or just select from inside the class.

In C++11 you can qualify the enumerators with the name of the enum, giving padData::buttonsAndAxes::select from the outside and buttonsAndAxes::select from inside.

---

Printing the name of an enumerator is not easily done in C++, because the names are gone after compilation. You need to set up a table mapping the values to their strings by hand. If you don’t supply explicit values like in your example, you can simply use an array:

enum buttonsAndAxes
{
    select,
    start,
    ps
};

const char* buttonsAndAxesNames[] = {
    "select",
    "start",
    "ps"
};

And then you index into that array:

 printf("%s", buttonsAndAxesNames[select]);

If you want some more sophisticated approach, you can find a bunch of tricks in previous questions.