How to pass class instance pointer to callback function?

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Class function sets the hook for mouse events.
How to pass specific class instance pointer to callback function LRESULT CALLBACK MouseProc?
Thanks!

Posted 9-Sep-14 20:44pm

Igor-84

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CPallini · Answer 1 · 2014-09-09T21:06:00

Solution 1

As far as I know, you cannot do that, since there is no way to pass data to the MouseProc callback. However, you could export your class instance, using, for instance, a static method.

Posted 9-Sep-14 21:06pm

CPallini

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Igor-84 10-Sep-14 3:11am

CPallini, can you write a small example which would help me to understand. Thanks!

CPallini 10-Sep-14 3:36am

You may have a look at Singleton design pattern, for instance (you haven't to implement it, but your code would be very similar).

Igor-84 10-Sep-14 3:52am

CPallini, I don't understand how it can help me...

CPallini 10-Sep-14 4:02am

The callback can only access global variables or static methods. So these are your alternatives.

Igor-84 10-Sep-14 9:04am

As far as I understand, a singleton pattern can work with only one instance of the class. And in my case there will be created a lot of copies. Can you give an example of code? Thanks!

CPallini 10-Sep-14 9:22am

Just add a parameter to the getInstance method to let it know what instance do you need.