Signals and slots implementation in Delphi?

Question

Does an implementation of the signals and slots mechanism for event dispatching exist for Delphi?

Answer 1

Search for multicast events. There are a few implementations out there, e.g.

• http://www.deltics.co.nz/blog/?p=137
• http://blogs.embarcadero.com/abauer/2008/09/03/38867
• http://www.codebot.org/delphi/?doc=9568

Some of them need generics, so are D>2009 only.

Answer 2

Whilst you can implement multi-cast events yourself, they are not directly supported in the the language unlike in C# and VB.NET. Lack of language support makes any attempt to emulate multi-cast events rather clumsy.

Interestingly, C++ lacks support for signals and slots and the Qt solution involves an extra process in the compilation tool chain, the Meta Object Compiler.

Answer 3

I spent some time a while ago getting Allen Bauer's Multicast Event code working. It has some limitations, but works well in my code. You can see the code here.

Of course, it only works in Delphi > 2009