Signals and Slots in D

[Georg Wrede]

Walter Bright wrote:
> Ok, before anyone jumps on me, this has all been discussed in 
> http://www.digitalmars.com/d/archives/28456.html
> 
> Looks like the deletion problem is a real issue. Let me think about it a 
> bit.

Hmm. A "big" SS implementation (see previous thread here "Dissecting the 
SS") c.f. like the 111 case, has more deletion related issues.

In a non-trivial application one can almost take it for granted that 
there's instance pooling going on, too.

A robust implementation would guarantee that any way the observer gets 
"removed" guarantees it also ceases to exist as an observer. This includes

  - getting deleted
  - simply not being referred to anymore
  - getting moved to the unused instances pool