forward declaration of a structure nested in a class

[Stephane Routelous]

Hi,

I would like to make a forward declaration of a strcuture nested in a class.
I have

file A.h
class A
{
public:
struct B
{
};
};

file C.h
class C
{
public:
static doIt(const A::B& object);
};

I tried :
struct A::B;
but it doesn't work ( MSVCPP 6.0 last SP )

Is it a way to do that ?

thanks in advance,

Stephane Routelous

[John Carson]

Re: forward declaration of a structure nested in a class

"Stephane Routelous" <nobody@nowhere .com> wrote in message
news:c12rnn$kik $1@dns3.cae.ca[color=blue]
> Hi,
>
> I would like to make a forward declaration of a strcuture nested in a
> class. I have
>
> file A.h
> class A
> {
> public:
> struct B
> {
> };
> };
>
> file C.h
> class C
> {
> public:
> static doIt(const A::B& object);
> };
>
> I tried :
> struct A::B;
> but it doesn't work ( MSVCPP 6.0 last SP )
>
> Is it a way to do that ?
>[/color]

No, the only type of forward declaration allowed for a nested class is one
inside the enclosing class, e.g.,

class Outer
{
// forward declaration of inner class
class Inner;
// other stuff
}

// full declaration of inner class
class Outer::Inner
{
// Inner stuff
};


--
John Carson
1. To reply to email address, remove donald
2. Don't reply to email address (post here instead)

[Gianni Mariani]

Re: forward declaration of a structure nested in a class

Stephane Routelous wrote:[color=blue]
> Hi,
>
> I would like to make a forward declaration of a strcuture nested in a class.
> I have
>
> file A.h
> class A
> {
> public:
> struct B
> {
> };
> };
>
> file C.h
> class C
> {
> public:
> static doIt(const A::B& object);
> };
>
> I tried :
> struct A::B;
> but it doesn't work ( MSVCPP 6.0 last SP )
>
> Is it a way to do that ?[/color]

No.

You might be able to use a template, i.e.:

class A;

class C
{
public:
template <class tA>
static int doIt(const typename tA::B & object);
};


class A
{
public:
struct B
{
};
};


template <>
int C::doIt<A>(cons t A::B & object)
{
}


oops now I'm not sure you can specialize outside of the class
declaration - this one is new to me.

[Gianni Mariani]

Re: forward declaration of a structure nested in a class

Gianni Mariani wrote:[color=blue]
> Stephane Routelous wrote:
>[/color]

.... Sorry I'd suggest you do it this way below - that way you don't need
to specify the <A> in doit<A>.


class A;

class C
{
public:
template <class tA_B>
static int doIt(const tA_B & object);
};


class A
{
public:
struct B
{
};
};


template <>
int C::doIt<A::B>(c onst A::B & object)
{
return 0;
}


int main()
{
A::B x;

C::doIt( x );
}

[color=blue]
>
> oops now I'm not sure you can specialize outside of the class
> declaration - this one is new to me.
>[/color]

I'm still not sure this is legal but g++ (3.4prerel) works fine with it.

[Stephane Routelous]

Re: forward declaration of a structure nested in a class

I tried that, but I got a beautiful internal compiler error with vc++6.0

Thanks,

Stephane

"Gianni Mariani" <gi2nospam@mari ani.ws> wrote in message
news:c12vi7$kkc @dispatch.conce ntric.net...[color=blue]
> Gianni Mariani wrote:[color=green]
> > Stephane Routelous wrote:
> >[/color]
>
> ... Sorry I'd suggest you do it this way below - that way you don't need
> to specify the <A> in doit<A>.
>
>
> class A;
>
> class C
> {
> public:
> template <class tA_B>
> static int doIt(const tA_B & object);
> };
>
>
> class A
> {
> public:
> struct B
> {
> };
> };
>
>
> template <>
> int C::doIt<A::B>(c onst A::B & object)
> {
> return 0;
> }
>
>
> int main()
> {
> A::B x;
>
> C::doIt( x );
> }
>
>[color=green]
> >
> > oops now I'm not sure you can specialize outside of the class
> > declaration - this one is new to me.
> >[/color]
>
> I'm still not sure this is legal but g++ (3.4prerel) works fine with it.
>[/color]

[Gianni Mariani]

Re: forward declaration of a structure nested in a class

Stephane Routelous wrote:[color=blue]
> I tried that, but I got a beautiful internal compiler error with vc++6.0[/color]

vc++6.0 is too old. Time to upgrade to GCC ... :-)