way of defining class in a namespace

Question

I defined a class in a namespace in a header as follows

#ifndef _c1_
#define _c1_

namespace classspace
{
    class Aclass;
}

class Aclass
{
    //body
};

         


        

Answer 1

Imagine

namespace foo
{
  class AClass;
}
namespace goo
{
  class AClass;
}

class AClass
{
}

int main()
{
  AClass myClass;
}

Which one are we using? foo or goo?

You must specify, either by calling all uses of AClass with the namespace name, i.e foo::AClass, or by placing all uses of it inside

namespace foo
{

}