Best way to use a derived member as a template parameter to a base

[Andy Champ]

What I want to do (and can't...) is

Template <typename Tclass base
{
// whatever
}

class derived: public base<derived::m yVals>
{
Enum myVals
{
// this isn't relevant either
}
}

....so that I can have a function in the base that takes the enum as a
parameter.

At the moment I'm running with a helper class that contains the enum
(and nothing else); but it's ugly, because it separates the enum from
its proper class. What do people think is the best way around this?

Ta
Andy

[Victor Bazarov]

Andy Champ wrote:

What I want to do (and can't...) is

Template <typename Tclass base
{
// whatever
}

class derived: public base<derived::m yVals>
{
Enum myVals
{
// this isn't relevant either
}
}

...so that I can have a function in the base that takes the enum as a
parameter.

At the moment I'm running with a helper class that contains the enum
(and nothing else); but it's ugly, because it separates the enum from
its proper class. What do people think is the best way around this?

No way around this. You cannot use a member of the class *before*
defining the class itself (and the member).

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[mlimber]

On Aug 14, 3:28 pm, Andy Champ <no....@nospam. comwrote:

What I want to do (and can't...) is

Template <typename Tclass base
{
// whatever

}

class derived: public base<derived::m yVals>
{
Enum myVals
{
// this isn't relevant either
}

}

...so that I can have a function in the base that takes the enum as a
parameter.

At the moment I'm running with a helper class that contains the enum
(and nothing else); but it's ugly, because it separates the enum from
its proper class. What do people think is the best way around this?

Use a namespace to group the enum and the derived class.

Cheers! --M

[Tonni Tielens]

On Aug 14, 9:28*pm, Andy Champ <no....@nospam. comwrote:

What I want to do (and can't...) is

Template <typename Tclass base
{
// whatever

}

class derived: public base<derived::m yVals>
{
* * * * Enum myVals
* * * * {
* * * * * * * * // this isn't relevant either
* * * * }

}

...so that I can have a function in the base that takes the enum as a
parameter.

At the moment I'm running with a helper class that contains the enum
(and nothing else); *but it's ugly, because it separates the enum from
its proper class. *What do people think is the best way around this?

One other way to do this is to put the enum in a separate wrapper
class before you define your Derived class. Something like:

struct MyValues
{
enum MyValuesEnum
{
// Your values here.
};
};

class Derived : public Base<MyValues:: MyValuesEnum>
{
// You're class members here.
};

Good luck.

[Andy Champ]

mlimber wrote:

>
Use a namespace to group the enum and the derived class.

Cheers! --M

I've nearly taken your advice. Something like this:

namespace espace
{
enum base { base1, base2, etc };
}

template <typename Tclass base
{
public:
void someFunc(T param);
....
}

namespace espace
{
enum derived1
{
value1 = base1,
value2 = 1000 /* to keep it well clear of base */
etc
}
}

class derived1: public base<espace::de rived1>
{
....
}

namespace espace
{
enum derived2
{
value1 = base2,
value2 = 1000 /* to keep it well clear of base */
etc
}
}

class derived2 public base<espace::de rived2>
{
....
}

I can use derived1::someF unc with espace::derived 1 and
derived2::someF unc with espace::derived 2, and it type checks - so this
is good enough.

Thanks guys

Andy