无法在 Visual Studio 2022 中包含 .cpp 和 .h 文件

Question

I have created a class Dialog and separated it into.cpp (Dialog.cpp) and.h (Dialog.h). My cpp file looks like this:

#include "Dialog.h"
#include <iostream>
using namespace std;

namespace Model1
{
    void Dialog::initialize ()
    {
          cout << "initialization";
    }
}

And here is my h file:

using namespace std;
class Dialog
    {
        public:
            void initialize ();
    };

When I debug the code in visual studio 2022 I get this:

cannot open source file "Dialog.h"
name followed by '::' must be a class or namespace name
Cannot open include file: 'Dialog.h': No such file or directory ConsoleApplication1 
symbol cannot be defined within namespace 'Model1'  ConsoleApplication1

When I changed my header file to

using namespace std;
namespace Model1 {
    class Dialog
    {
    public:
        void initialize();
    };
}

And now I have these errors:

cannot open source file "Dialog.h"
name followed by '::' must be a class or namespace name
Cannot open include file: 'Dialog.h': No such file or directory 

How can I fix the problem?

Answer 1

The problem is that in the header file you've defined class Dialog in global namespace while you're trying to define the member function Dialog::initialize() in Model1 namespace.

This will not work because the out-of-class definition for the member function of a class must be in the same namespace in which the containing class is .

Thus, to solve this you can either define the class(in the header) in namespace Model1 or implement the member function(in the source file) in global namespace. Both these methods are shown below:

Method 1

Here we define the class in namespace Model1 in the header and leave the source file unchanged .

dialog.h

namespace Model1   //added this namepspace here
{
class Dialog
    {
        public:
            void initialize ();
    };
}

Working demo 1

---

Method 2

Here we define the member function in global namespace in source file and leave the header file unchanged .

dialog.cpp

#include "Dialog.h"
void Dialog::initialize ()
{
      cout << "initialization";
}

Working demo 2