Re: OO architecture in MFC

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 18 Aug 2006 21:03:08 -0400

Message-ID:

<e4qiysywGHA.2204@TK2MSFTNGP03.phx.gbl>

PaulH wrote:

I have an MFC app that can be used with or without the dialog (GUI)
component. The dialog is an optional status component that updates with
statistics every second. I'd like to put all the statistical
calculations and queries in the App. The Dlg and the App run in two
separate threads.

My question is: what's the best OO method of doing this?

1. Do I put a timer in the dialog and have it get the data from the app
every second?
CMyDlg::OnTimer()
{
   STATISTICS stats;
   ((CMyApp *)GetParent())->GetStatistics(&stats);
   //...
}

2. Do I send a pointer to the statistics to the dialog from the App and
just have the dialog read that every second?
CMyApp::CreateDialog(CWnd *pParent)
{
  m_pDialog = new CMyDlg();
  m_pDialog->SetStatisticsPointer(&m_statPointer);
  m_pDialog->Create(IDD_MY_DLG, pParent);
  //...
}

Neither of these strikes me as a particularly fantastic solution... Is
there a better way?

Thanks,
PaulH

There's no real OO difference between these approaches. They both
access the app from the dialog, just using two different ways to get the
pointer. But the dependency is the same.

By the way, GetParent does not return the app. Global function
AfxGetApp() will get the app pointer.

When dealing with interthread communication you need to synchronize
access to the shared data. An elegant solution for avoiding the
necessity for this is to have the thread post the data to the dialog,
passing a pointer to a heap-allocated STATISTICS struct. 'new' it in
the thread every time, and delete it in the dialog message handler.
This gives you free interthread queueing and synchronization as well as
a dependency only on the STATISTICS struct.

--
Scott McPhillips [VC++ MVP]