Getting to know PixLib

Theres more and more frameworks available for flash developers these days and choosing between them isnt easy, mainly because they all share one feature. No documentation. At least no documentation that you could read to understand what the framework is about unless you like reading API docs.

So, in an effort to get to know more about them the only choice is to try and use them and write about what i find. Im going to start with PixLib as it does have API docs which gives a rough idea of the area it covers and its in active development.

I’ve got real world projects im working on which need some functionality which is available in PixLib. The choice is then, either code it myself or learn the PixLib way. Im going to try it with PixLib and see if it saves me time over the code-it-myself approach (which is what I normally do…I tried ARP before but didnt like the way it was structured so i coded my own micro-architecture which im happy with at the moment)

My first task for PixLib : Loading configuration files.

I need to load in a configuration file at the start of my application and have access to the configuration data throughout my app. I already have my own config file reader which I built it when i just needed a simple key => value mapping but its not good enough anymore.

A quick scan of the API docs reveals a few interesting Classes : Config, ConfigLoader and ConfigLoaderEvent.

Looks like the ConfigLoader is a good place to start and theres a method there which unsurprisingly is called ‘load’.

I’ve already downloaded the PixLib source and unzipped it into my classpath, so now its time to investigate the source 🙂

The constructor of the ConfigLoader takes 2 arguments, an object called config which looks like it will be used to store the config and a deserializer to convert the xml to an object representation. But, before we jump in and start to create the loader one important thing you’ll notice about PixLib is that if you dont supply arguments then it uses sensible defaults. This is great as it saves a lot of wasted time which would be spent looking into other Classes to see how to build them and pass them in etc.

The next vital part of the puzzle is how do we know when the config has been parsed?

Back to the API docs and we can see the ConfigLoader has an onLoadInitEVENT which sounds just like what I need.

So the code i think i’ll need to load the config and get notification will look like this :

configLoader = new ConfigLoader();
configLoader.addEventListener(ConfigLoader.onLoadInitEVENT,this,configLoaded);
configLoader.load();


N.B. I have updated the above code because Francis (the creator of PixLib) kindly pointed out that PixLib automatically creates delegates when you register event listeners. So no need to use an external delegate factory. More bonus points for PixLib.

The ConfigLoader uses a url of ‘config.xml’ by default (im always happy to favour convention) so no need to supply any arguments to the load method.

I’ve added my handler (configLoaded) so now I need to find out how to access my configuration data.

Back to the API, this time to the Config class. Looks like this is a Singleton so I can access it from anywhere and know its the same instance. So just a quick call Config.getInstance() and i’ve got access to my configuration data, converted from xml to a nice round object. Great.

As I said earlier I need a bit more structure in my config than just name – value pairs. Some items need to have properties, some just need to exist.

From looking at the source earlier I saw that the ConfigLoader uses an XMLToObjectDeserializer so im going to go and investigate what happens inside the deserializer.

Right at the top theres some calls to ‘addType’ which seems to be used for mapping types to deserialization routines, but how do I specify those types in my config? (number, string, array among others)

A quick scan of the deserialize function shows

var dataType:String = node.attributes.type;

ah, so I use an attribute called ‘type’ to declare the type of the node, and im guessing that the node value represents the node value (seems reasonable)

Time to edit my config.xml and see if the data comes through how I want it. Here’s what I have so far :

  
    
      
        477
        277
      
    
  

Then its just a quick check with some trace statements in the config load event handler and we’re done.

trace(Config.getInstance().artifacts.backgrounds.size.width);

Output : 477


Perfect.

How do I think PixLib stood up to the task overall?

It required a bit of investigation and API / source code reading to find out what I needed but it probably took a little less time than building my own AND is a lot more flexible than what I would have built in the time.
Also the PixLib source code is clear and relatively easy to understand. The use of defaults is very well done and makes using the library pretty much painless.

Definitely a thumbs up.

A quick summary for those of you who cant be bothered to read everything.

1. Create a ConfigLoader and load your data

configLoader = new ConfigLoader();
configLoader.addEventListener(ConfigLoader.onLoadInitEVENT,Delegate.create(this,configLoaded));
configLoader.load();

2. Get the Config instance and use your data

mc._width = Config.getInstance().artifacts.backgrounds.size.width