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Yet another approach to Delegates in unmanaged C++

By , 5 Mar 2002
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Sample Image - cppDelegate.gif

Introduction

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
{
public:
	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.

License

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.

A list of licenses authors might use can be found here

About the Author

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

Comments and Discussions

 
QuestionDownload link is down... PinmemberGhostEx27-Jan-13 23:58 
GeneralStraightforward and useful PinmemberYves Tkaczyk21-Oct-05 10:50 
GeneralRe: Straightforward and useful PinmemberMizan Rahman24-Sep-13 1:51 
GeneralRe: Straightforward and useful PinmemberYves Tkaczyk7-Oct-13 7:14 
GeneralRe: Straightforward and useful PinmemberMizan Rahman7-Oct-13 22:21 
GeneralRe: Straightforward and useful PinmemberYves Tkaczyk8-Oct-13 8:13 
GeneralExcellent work PinmemberVerifier19-Nov-03 3:08 
GeneralShould not mix C/C++ with .NET PinmemberTW23-May-03 0:04 
Generalthreads.. Pinmembersaltynuts200225-Feb-03 18:32 
Generalget the code to run under VS.NET PinmemberTweety30-Jan-03 6:54 
GeneralRe: get the code to run under VS.NET PinmemberYuetKent24-Aug-04 23:01 
GeneralRe: get the code to run under VS.NET PinmemberTweety26-Aug-04 3:05 
GeneralFairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberAnonymous10-Apr-02 13:24 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberCachivache15-May-02 17:20 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberM Aamir Maniar10-Mar-03 17:32 
I totaly agree with you.
 
m aamir maniar
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinmemberCholo15-Mar-03 4:53 
GeneralRe: Fairly named "Standard C++" instead biased ads "unmanged C++" ! PinsussCholo Lennon15-Mar-03 4:53 
GeneralWell I don't agree! PinmemberChryler21-Jul-03 21:29 
GeneralRe: Well I don't agree! PinmemberPaul Selormey4-Sep-03 3:09 

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