yikulju

Recently, I’ve been working on the ZuiPrezi client side backend and there are loads of asynchronous requests for resources, which are, to be precise, a pain in the arse.

For instance, if I need “Arial” and then “Verdana” and then a presentation in this order, I would write something like this:

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backend.getFont("arial", function(data:Font):void
{
 
	backend.getFont("verdana", function(data:Font):void
	{
		backend.loadPresentation(12)
	})
})

Pseudo solution

The way I would describe it in pseudocode could be like this:

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getFont("arial")
then
getFont("verdana")
then
getPresentation(12)

AS3 solution

Let’s make it more AS3 like:

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new Chain( { arg: "arial", command: getFont }, 
                 { arg: "verdana", command: getFont }, 
                 { arg: 12, command: getPresentation }
);

Although it works, I don’t like the syntax very much. We can make it better.

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(new Chain()
		.execute("arial", loadFont)
		.execute("verdana", loadFont)
		.execute(12, getPresentation)
);

Parallelism

One more thing, does it support parallelism, It does.

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(new Chain()
	.begin
		.execute("arial", loadFont)
		.execute("verdana", loadFont)
		.execute(12, getPresentation)
	.end
	.begin
		.execute("helvetica", loadFont)
		.execute("futura", loadFont)
		.execute(1, getPresentation)
	.end
);

Here you can download the sourecode.

Finally, If I want to sum up how it works, here is an overall figure:
Everything within begin - end happens synchronously, one by one,
and every begin - end pair runs simultaneously.

What do you think?

Finally, there is an interesting article by John Resig about Chaining with JQuery.

This post is tagged as3, chaining