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Asked: 2026-05-15T05:25:57+00:00

I am thinking about elegant way to encapsulate WinAPI callbacks inside a class. Suppose

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I am thinking about elegant way to encapsulate WinAPI callbacks inside a class. Suppose I am making a class handling asynchronous I/O. All Windows callbacks should be stdcall functions, not class methods (I need to pass their addresses to ReadFileEx WinAPI function for example). So, I cannot just pass method addresses as a callback routines to WinAPI functions.

What is the most elegant way to encapsulate functionality of this type inside a class so that the class have events OnReadCompleted and OnWriteCompleted (I am using Delphi as a primary language, but I guess the situation must be the same in C++ because class methods are different from simple methods by the fact, that the first hidden parameter of them is this link. Of course this class is not a singleton and there can be many of them created by app at the same time.

What do you think would be the good way to implement this?

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1 Answer

  1. Editorial Team

    I doubt this is in any way elegant but, IMO, the easiest is to convert the address of a method of a class to a procedure address and pass it to the winapi. Sure, it’s a hack, but the VCL does the very same with classes.MakeObjectInstance, if only for a specific construct.. See this question for a source for this kind of implementaion and some other, more OO ways to handle the situation.

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