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

Namespaces are essentially packages. In your Qt example, the class is forward declared. One way to use namespaces is as follows:

namespace MyNamespace
{
  class MyClass
  {
  };
}

If you want to do it like your first example, then you must forward declare it. For example,

namespace MyNamespace
{
   class MyClass;
}

class MyClass
{
    //body
};