Signals and Slots

[Frits van Bommel]

Sean Kelly wrote:
> Frits van Bommel wrote:
>>
>> If we replace this line by:
>>               {  slots_idx--;
>>                  dg = slots[slots_index];
>>                  slots[slots_idx] = null;
>> then we don't need to check for empty slots in emit():
>> If slots.length == slots_idx, we can be sure the array is full.
>>
>> (Unless there's a requirement for the slots to be
>> called in any particular order?)
> 
> No, but the sequence may need to be modified while emit is processing. 
> Consider a slot that disconnects itself when it receives a signal.  But 

Yeah, that can create some extra headaches, of course.

> I suppose you could do something like this:
> 
> void emit( T1 i )
> {
>     {
>         isEmitting = true;
>         scope(exit) isEmitting = false;
> 
>         foreach( s; slots )
>             s(i);
>     }
>     foreach( s; disconnects )
>         disconnect( s );

You may want to add
     disconnects.length = 0;
or
     disconnects = null;
here.

> }
> 
> void disconnect( slot_t s )
> {
>     if( !isEmitting )
>     {
>         // remove from slots
>         return;
>     }
>     disconnects ~= s;
> }
> 
> Things get even worse in a multithreaded app [...]

They always do ;)
Seriously, I think if your app is multithreading you're probably going 
to have to synchronize most things that can be accessed by multiple threads.
Since the original implementation was not thread-safe I saw no reason to 
make my modifications so.