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From: Gianni Mariani <gi2nospam@mariani.ws>
Date: 26 Jul 2003 04:52:43 GMT
Newsgroups: comp.lang.c++
Subject: Re: enum count
Clive wrote:
> If you have an enum, is there any way during execution to find the number of
> values in the enum?
> Say I have,
>
> enum great { five, ten, fifteen };
>
> How could I get the number 3 from that?
>
>
replace the enums with objects that report themselves to a registry.
I have done it in the past using a template ...
templace <typename base>
class ExposedEnum : public base
{
public:
int enum_val;
ExposedEnum( int number )
: enum_val( number )
{
ExposedEnumRegister<base>::Register( *this );
}
ExposedEnum( int number )
: enum_val( ExposedEnumRegister<base>::GetNextNumber() )
{
ExposedEnumRegister<base>::Register( *this );
}
// some more stuff ...
operator int () const
{
return enum_val;
}
explicit ExposedEnum( const ExposedEnum & foo );
};
template <typename base>
class ExposedEnumRegister
{
static int GetNextNumber ....
static void Register ....
static int Count ....
}
Now you can forward declare them...
extern ExposedEnum< great > five;
extern ExposedEnum< great > ten;
extern ExposedEnum< great > fifteen;
In a cpp file you can instantiate them.
ExposedEnum< great > five( 5 );
ExposedEnum< great > ten( 10 );
ExposedEnum< great > fifteen;
Now, if you want to know how many you have :
ExposedEnumRegister< great >::Count();
Disclaimer - it's an outline only, yes it's incomplete.
G
$Id$
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