Event Dispatcher

[Eugene Wissner via Digitalmars-d-announce]

On Wednesday, 16 March 2016 at 15:14:57 UTC, Kagamin wrote:
> On Thursday, 10 March 2016 at 18:08:15 UTC, Eugene Wissner 
> wrote:
>> Why not just extend the HelloWorld class and override the 
>> hello()? Imagine you write an apllication that should support 
>> plugins. And two independent plugins extend the HelloWorld. 
>> One plugin would conflict with the another. EventDispatcher 
>> make it possible to register the events that can be used by 
>> application plugins.
>
> How about something like MEF?

I didn't know about MEF before, I've just read an article about 
it, so correct me if I'm wrong. I think that MEF and such event 
dispatcher aren't comparable. Event dispatching is one of the 
principles how to extend the application. MEF as Wikipeda states 
"aims to solve the runtime extensibility problem". The important 
word is "runtime". So it is a higher level, it is about binding 
different parts of application at runtime. (As I understand it).

Now Symfony, I'm inspired by, has a thing called Bundles. Bundles 
are just application plugins. And event dispatching can be used 
inside this bundles aswell. And it is the level where something 
like MEF would be really great. I think it should be really done, 
because it would make it possible for example to write closed 
source plugins for open source applications (it is very common in 
ecommerce, for example online shops, even for PHP, where you can 
decode your plugins with something like ioncube).

Another area, where it could be used, is routing (already because 
plugins should be able to add routes to the application at 
runtime).

So concepts like MEF are anyway something very useful for 
compiled applications/languages and I'll have to find a way to 
implement it on some stage. Thanks for mentioning it.