https://gist.github.com/9aeb57a266c7435684ef

private var heroAdded:FunctionSignal1 = new FunctionSignal1();
 
// add 'listeners' like this
heroAdded.addSlot(onHeroAdded);
 
// remove it like this:
heroAdded.removeSlot(onHeroAdded);
 
private function onHeroAdded(hero:Object):void 
{
    trace("cool, there is a hero added");
}

I don’t know if this is performing as fast as the normal Signal1 with a FunctionSignal, haven’t tested that, but I think this is more useable in normal projects since you can normally pass the listener function.

var heroFunctionSlot:FunctionSlot1;
 
heroAdded.addSlot(heroFunctionSlot = new FunctionSlot1(onHeroAdded)); // add slot
 
heroAdded.removeSlot( heroFunctionSlot );

It would be great if there is an alternative to this. Maybe a FunctionSignal or something would be a great addition, which creates FunctionSlots inside the class like addSlot(func);

Signals should perform the same when they are static, but the static lookup (e.g. MyGlobalSignals.enterFrame) is more expensive.

I have explorer the classes to see how it worked. I am not a performance expert but I think some small things could be improved.
- Use vectors instead of arrays (who uses fp9 anyway)
- Optimise the dispatch function:
- Remove the var from function, and if you use a vector, there would be no need to cast to type inside the loop.
- Remove the default value 0 of i

public function dispatch(arg:*): void
{
    __slotsNeedCopying = true;
    __numDispatchesInProgress++;
    for (var i:uint, len:uint = __slots.length; i < len; ++i)
    {
        __slots[i].onSignal1(arg);
    }
    __numDispatchesInProgress--;
    if (__numDispatchesInProgress == 0)
    {
        __slotsNeedCopying = false;
    }
}

I don’t see any reason why __numDispatchesInProgress counts up and down in the same function, It will always end as 0? What does slotsNeedCopying mean?

I think the signals are a very great concept. I really like the fact you don’t have to create event-types (Strings), but the signals describe the event itself. They are just very simple. (clicked:Signal).

BTW In most of my apps I create a singleton which extends EventDispatcher, to have global events (bad, but very very handy ☺). How do signals perform when they are static?

I’ve updated the article to actually create the signals and to remove the type from the Signal1 callback, which is unfortunately necessary for compilation. If you want to get the type back, you’ll need to do a cast. Also, if you use a FunctionSlot to mimic the EventDispatcher or as3signals approach, you can still type the parameter. You give up some speed—as shown in the article—and some compile-time checking—it can’t make sure your arguments are of the correct types, the same problem you have with EventDispatcher and as3signals—but you do at least get to give your argument an explicit type.

I wish I know of a way that was fast, flexible, and type-safe. Unfortunately, AS3 seems to force compromise here:

• fast, type-safe – TurboSignals with the types explicitly stated instead of using *
• fast, flexible – TurboSignals
• flexible, type-safe – No solution?

The key seems to be that all of AS3′s dynamic functionality disposes of all the compile-time checking.

The clicked Signal1 never gets instantiated and gives an object-null error when trying to call the addSlot function. For the example it would be an idea to add somewhere ‘new Signal1()’

Another thing which cost me more time to explore;

I have a class called Enemy, which have a Signal1. I also have a class called Game which implements Slot1.
When I use a type in the onSignal1 function in the Game class like this:

/* INTERFACE com.jacksondunstan.signals.Slot1 */
public function onSignal1(enemy:Enemy):void

..I get this Error: “Interface method onSignal1 in namespace com.jacksondunstan.signals:Slot1 is implemented with an incompatible signature in class Game.”

It is fixed when I use this, but then I lose my completion:

/* INTERFACE com.jacksondunstan.signals.Slot1 */
public function onSignal1(enemy:*):void

How is it possible your example uses a type at that place?

I am using flex_sdk_4.1.0.16076, compiling as FP10.1