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Yet another approach to Delegates in unmanaged C++

, 5 Mar 2002
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Asynchronous delegates in unamanaged C++ using the C# syntax
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Sample Image - cppDelegate.gif


Ben Chan introduced a way of simulating delegates in unmanaged code. Although his method works I wanted to have a syntax similar found in the C# language. I also wanted to be able to use async delegates.

Using my solution

Defining a Delegate is simple as this:

Delegate OnBtnClick;
AsyncDelegate OnNewMail;

To add a new delegate handler to those defined above you have to choose whether you want to use a static/global function or a member function. To subscribe a delegate you use a syntax similar to C#'s:

class MyClass
	void Handler1(LPVOID source, DelegateArgs* args)

	static void StaticHandler(LPVOID source, DelegateArgs* args)

void main()
	MyClass instance;
	Delegate OnBtnClick;

	OnBtnClick += NewClassDelegateHandler(MyClass, instance, Handler1);
	OnBtnClick += NewDelegateHandler(&MyClass::StaticHandler);

	LPVOID source = 0;
	DelegateArgs* args = 0;

	// you can also remove a delegate handler from the invocation list
	// OnBtnClick -= NewClassDelegateHandler(MyClass, instance, Handler1);

	OnBtnClick.Invoke(source, args);

NewClassDelegateHandler and NewDelegateHandler are defines that create the appropriate DelegateHandler class. It can be the StaticDelegateHandler for static functions or ClassDelegateHandler for member functions.

The async delegate only overrides the Delegate::Invoke method by creating a thread to invoke the handlers. You can make your delegate thread safe (AsyncDelegate already is) by defining a Delegate like this Delegate ThreadSafeDelegate(true);

IMPORTANT: To use my solution you have to enable runtime type information in your project.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Architect VisionOne AG
Switzerland Switzerland
XicoLoko is a brazilian developer based in Switzerland.

Comments and Discussions

QuestionDownload link is down... PinmemberGhostEx28-Jan-13 0:58 
GeneralStraightforward and useful PinmemberYves Tkaczyk21-Oct-05 11:50 
Thank you for your code. Amongst all the VC++ delegate implementation, I think it is the simplest and also has the merit to work with VC++ 6.0.
I have templatized it to add typed safety for the event arguments (no need to derived from DelegateArgs anymore and no need to cast).
The only thing I would like to simplify now is the delegate handler registration. I will post the update when I am done.
Thanks again,
Yves Tkaczyk
GeneralRe: Straightforward and useful PinmemberMizan Rahman24-Sep-13 2:51 
GeneralRe: Straightforward and useful PinmemberYves Tkaczyk7-Oct-13 8:14 
GeneralRe: Straightforward and useful PinmemberMizan Rahman7-Oct-13 23:21 
GeneralRe: Straightforward and useful PinmemberYves Tkaczyk8-Oct-13 9:13 
GeneralExcellent work PinmemberVerifier19-Nov-03 4:08 
GeneralShould not mix C/C++ with .NET PinmemberTW23-May-03 1:04 
Generalthreads.. Pinmembersaltynuts200225-Feb-03 19:32 
Generalget the code to run under VS.NET PinmemberTweety30-Jan-03 7:54 
GeneralRe: get the code to run under VS.NET PinmemberYuetKent25-Aug-04 0:01 
GeneralRe: get the code to run under VS.NET PinmemberTweety26-Aug-04 4:05 
GeneralFairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberAnonymous10-Apr-02 14:24 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberCachivache15-May-02 18:20 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberM Aamir Maniar10-Mar-03 18:32 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberCholo15-Mar-03 5:53 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinsussCholo Lennon15-Mar-03 5:53 
GeneralWell I don't agree! PinmemberChryler21-Jul-03 22:29 
GeneralRe: Well I don't agree! PinmemberPaul Selormey4-Sep-03 4:09 

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