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Sample c++ code (subscribe, error handling, MFC)

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11 Sep 2014 06:11 #2267 by support
Replied by support on topic Sample c++ code (subscribe, error handling, MFC)
I am sorry, we do not have such example; you will be on your own if you want to go this way.

In my view, however, if you have a MFC application, you can use the code we provided just well - that is, combine the code from the example with your existing MFC code. MFC and ATL are now considered a single library by Microsoft, and the reason we chose the "ATL" approach for our examples is because it works best (I am not sure if it can be done the "pure MFC" way).

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11 Sep 2014 06:06 #2266 by support
Replied by support on topic Sample c++ code (subscribe, error handling, MFC)
From: OPC Labs Contact Form - R.
Sent: Thursday, September 11, 2014 2:10 AM
To: Zbynek Zahradnik
Subject: OPC Labs Contact Form - MFC Event handling

[...]
Please provide sample code that demonstrates how to set up asynchronous event messages using MFC. The sample code that I have seen up to this point is ATL based. It is slightly different in syntax from that of MFC. The sample code should have the following components:

1. Syntax for coding the message map

2. Syntax for initiating the asynchronous updates (advise method)

3. Syntax showing how to declare the class

4. Syntax showing how to declare the constructor

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10 Sep 2014 08:20 - 10 Sep 2014 08:23 #2261 by support
Replied by support on topic Sample c++ code (subscribe, error handling, MFC)
Dear Sir,

I have created a project that demonstrates the proper error handling and OPC quality recognition in the event handler.

The project file (SubscribeErrorHandling.zip) is attached to this post, and the most important part of the code (the ItemChanged event handler with the exception handling) is listed here:
Code:
// The handler for EasyDAClient.ItemChanged event STDMETHOD(ItemChanged)(VARIANT varSender, VARIANT varEventArgs) { _tprintf(_T("\n")); // Obtain the event arguments IEasyDAItemChangedEventArgsPtr EasyDAItemChangedEventArgsPtr(varEventArgs); // Display the item identification IDAItemDescriptorPtr DAItemDescriptorPtr(EasyDAItemChangedEventArgsPtr->ItemDescriptor); _tprintf(_T("Item ID: %s\n"), COLE2CT(_bstr_t(DAItemDescriptorPtr->ItemId))); // Test exception ICOMExceptionPtr ExceptionPtr(EasyDAItemChangedEventArgsPtr->Exception); if (ExceptionPtr != NULL) { _tprintf(_T("*** Error\n")); // Display the message and error code _tprintf(_T("Message: %s\n"), COLE2CT(_bstr_t(ExceptionPtr->Message))); _tprintf(_T("Error code: %d\n"), ExceptionPtr->ErrorCode); return S_OK; } // At this point, we know then there was no exception, and therefore the VTQ (value/timestamp/quality) will be present. IDAVtqPtr VtqPtr(EasyDAItemChangedEventArgsPtr->Vtq); _tprintf(_T("Timestamp: %s\n"), COleDateTime(VtqPtr->Timestamp).Format()); _tprintf(_T("Quality: %d\n"), VtqPtr->Quality); // A valid VTQ may contain no value, e.g. when the OPC quality is Bad. if (!VtqPtr->HasValue()) { _tprintf(_T("*** No value\n")); return S_OK; } // We can now access the value (as a VARIANT), in Vtq->Value. // This example just formats and displays the value using a function provided on the DAVtq object. _tprintf(_T("Value: %s\n"), COLE2CT(_bstr_t(VtqPtr->DisplayValue()))); return S_OK; }

I am not sure about the other parts of your question. Our events are not Windows messages, and my understanding is that therefore the MFC message maps cannot directly handle them.


Best regards
Attachments:
Last edit: 10 Sep 2014 08:23 by support.

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10 Sep 2014 08:17 - 10 Sep 2014 08:18 #2260 by support
Sample c++ code (subscribe, error handling, MFC) was created by support
From: OPC Labs Contact Form - R.
Sent: Wednesday, September 10, 2014 4:24 AM
To: Zbynek Zahradnik
Subject: OPC Labs Contact Form - Sample c++ code

[...]
Subject:
Sample c++ code

Note
Sample MFC code for Advise(Subscribe) with event notification(MESSAGE_MAP).



Sample Advise callback function that uses Exception interface.(extract error codes)
Last edit: 10 Sep 2014 08:18 by support.

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