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    <p>As I noted in the comments a couple of hours ago, you have several ways to resolve this issue:</p> <p>1) Use a higher-level library than the one you are currently using where you could preferably use signals and slots then as ideal in a Qt application.</p> <p>2) You could try passing your class instance as raw the data. This would ensure that the callback will have an object to work with. Of course, that would need reinterpret_cast'ing from the void* data to the desired type as usual.</p> <ul> <li>Establish property mutator and accessor methods to set and get the members</li> <li>Declare the callback function as friend, but that is usually discouraged.</li> <li>Just call a slot or simple method from the callback to do the job for you.</li> <li>Use a functor for doing the job</li> <li>etc...</li> </ul> <p>3) You could also implement the necessary logic yourself inside your project if is not too complex. That way, you could even reduce the dependency.</p> <p>It is difficult to say which approach would suit you the best as it depends a lot on the use cases and more context than we have here.</p> <p>I would probably go for either member data accessor and mutator methods, or a dedicated function in your class which does the real job, and the free callback function would just cast the void* to your type, and call the method on that instance.</p> <p>This would also ensure that you can use the callback with non-c++ code later as you would need to replace the internal implementation of it, only. This would also help later with getting rid of the external C callback which calls the class method.</p> <p>I think you should check out the following url where there is a relatively detailed sample code, where there is also a callback for similar issues with this low-level library.</p> <p><a href="https://codereview.stackexchange.com/questions/8840/ni-daqmx-c-wrapper-code-for-analog-data-acquisition-using-national-instrument">NI-DAQmx C++ wrapper code</a></p>
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    1. POmake a CVICALLBACK a member function in QT creator
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    1. CO2 is too complicated. If you need to have private data access, then you'll be able to make a static member function. Then you'll be able to access the internals as well.
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    2. CO@Vinzenz: your comments are obsolete. ;) The post has been edited before your posts. Luckily, I am getting a notification in my browser about such events.
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    3. COI am not wrong, it's entirely possible to do this. After reading your post a few times I seeing the point, however you structured your second point with sub points which makes it looks like a list of steps, you better change that. And if you down vote something, then explain at least why. Especially it's a valid example how you could solve this with normal C++, maybe it's not the Qt way.
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