forward declaration

[Vince]

Hi,

I have two classes that are mutually included So I Use forward declaration
and it works fine as long as I declare a pointer:

In WorkerThreadDemoDlg.h :


//forward declaration
class CMyThread;

class CWorkerThreadDemoDlg : public CDialog
{
public:
CWorkerThreadDemoDlg( CWnd* pParent = NULL ); // standard constructor

protected:
CMyThread* m_pCMyThread;
....
}

if I want to replace CMyThread* by a CMyThread it doesn't compile even if my
implementation I am not even using it.

 

[Victor Bazarov]

I have two classes that are mutually included So I Use forward declaration
and it works fine as long as I declare a pointer:

In WorkerThreadDemoDlg.h :


//forward declaration
class CMyThread;

class CWorkerThreadDemoDlg : public CDialog
{
public:
CWorkerThreadDemoDlg( CWnd* pParent = NULL ); // standard constructor

protected:
CMyThread* m_pCMyThread;
...
}

if I want to replace CMyThread* by a CMyThread it doesn't compile even if my
implementation I am not even using it.

Of course it doesn't. To know how big an object of 'CWorkerThreadDemoDlg'
should be, the compiler needs to know the size of every subclass and every
member object. If you don't have the definition of 'CMyThread' available
to the compiler, it can't figure out the size of 'CWorkerThreadDemoDlg'.

What did you expect, magic?