That’ll do for now…..

Sorry – I just realised……. Will fix soon as!

…..or is it?

Completely forgot that I had this picture.  I got this little Linux Penguin squeezy figure at a conference, and Charlie took a shine to it.  He was happily playing away with the penguin and then I turned my back for a second and this act of vandalism was committed.  Mind you it did say unbreakable……

I’m putting together a video player and I wanted to test the scrubber (the little button you use to drag the playback) was working.  More importantly I wanted to test it couldn’t be dragged further than the video had downloaded.  So I uploaded an flv to my site and tested the player.  This was fine the first time and then the stand alone player cached the flv, so I couldn’t test it anymore.  A quick google and I found this really handy tip.

I’ve started using Last.fm and it is fantastic!  I was listening to some Armand Van Burien when I scrolled down to see what other people thought about it.  As I was scrolling down my mouse rolled over one of the images as i was using firefox it displayed the alt (caption) text as flyout text.  In the case of Last.fm this turns out to be a description of the users details.

r34c7 – you are busted.

Had this quick gotcha the other day with flex builder and I thought I’d share – mainly for myself as I’ll no doubt forget this before too long.

I was working on a Flex Library Project.  Really cool you can work on classes in the Library project and as you save them they are compiled into a SWC file in the bin directory (as long as you have Build Automatically checked in the Project Menu, that’s another gotcha that drove me made for a bit when I turned it off as I was working on a large app and couldn’t be arsed to wait the 5 mins after each save whilst the compiler built the project.  Forgetting to turn it on or build the project gave me heartfailure when I launched the swf to test it was working.)  Anyway – back to Flex Library Projects generating SWCs.  Nice.  I can then share this, or just link to it and speed stuff up by using common code.

However I’d just added another folder and a few more classes to the Library project, saved them and then went off to the flex app I was building and started coding happily away.  Rather quickly I realised I wasn’t picking up the new classes I’d added to the SWC.  I checked in the Library Project, they were there.  I saved them again – thinking that sometimes maybe the SWC doesn’t compile.  I checked that Build Automatically was turned on (see above) it was.  I deleted the SWC and resaved the new classes.  Nothing happened.  Shit – I must have corrupeted somehow!  I decided to check on of the original classes – all fine, I saved it again and – hang on – there’s the SWC.  All compiled lovely.  Great!  Back to the flex app.

Nope – it still hasn’t compiled the new classes and packages into it and I have no access.  Right now I’m ready to throw the computer out of the window when I right click on the Library project, select Properties and then Flex Library Build Path.  Aha.  Even though I’ve added files and folders they ARE NOT added to the build path.  Click on them to select them, save – and there we go.  All sorted.

So long story short – if you’re compiling a swc using a Flex Library project and it’s missing packages and classes you know should be there, check the build path.

P.S.  I think I may be going bald with all the hair I’ve pulled out.

Ok, this morning on the way to work I stopped at my normal coffee place, grabbed my coffee and sat outside so i could have a ciggarette and wake up before a hard days coding (note that employers – a HARD DAY’s CODING).

I was watching the world go by and enjoying the Diggnation podcast when a deliver truck pulled up.  The blokie driving got out and walked round to the back smoking a fag himself (note to American readers this mean having a ciggarette, not shooting someone who’s made a different lifestyle choice) and when he got round to the back of the van he pocked the half smoked ciggarette up the exhast pipe for later while he made the delivery.  OK, I suppose it wasn’t high tar enough.  However the next bit really confused me – to make clear this guy was a normal bloke, wearing normal clothes, I’m pointing this out so you understand he had pockets.  He had his lighter in his hand.  Obviously like the ciggarette he needed to put it somewhere so he could load up the little trolley for his delivery.  So he stuck it in his shoe.  Not down the side next to his foot, in the sole…….. What sort of mental gymnastics do you make to decide that this is logically the best place to put it, bypassing all pockets on the way down?

Anyway – thought I’d share.

(Also had a wierd dream that Tor (the wife) died Charlie’s (the baby) hair and it all fell out.  It’s been a strange start to a Friday)

We’ve covered an overview of the MVC pattern and how it relates to Cairngorm and we’ve set up the environment and we’ve set up the environment so we can finally start to play with some code.  Nearly.

There is one last concept to go over before we move on, Singletons,  I’m sure that most of you are happy with this concept, but for those who don’t here we go.

A singleton is a class that there can only be one of.  Ever.  To borrow a joke from someone else – like Highlander there can be only one (though this analogy doesn’t quite add up as initially there were loads of them, then they had to fight each other to whittle the numbers down to one.  However the sequals made a mockerly of this idea as ‘aliens’ got involved in a typical WTF can we do now idea to make more money out of this clearly dead horse – and ruined a fantastic film.  So to relate this to a design pattern is actually quite misleading.) (Don’t get me started on the Matrix sequals – he had clearly won at the end of the first one, why didn’t you stop there?)

Right, sorry I do tend to digress a bit (Star Wars prequals!  WTF were they all about?  On a side note when I was an actor in the London Dungeon, long story but safe to say the acting career when fantastically well , I actually made the little boy who played Anakin Skywalker cry.  So I made Darth Vader cry – sort of.  Beat that!)

I did it again, concentrate – back to singletons.  Like I said a singleton is a class that there can be only one of.  Why is this helpful?  Well if there is only one then everytime you access the class you have exactly the same data stored within t.  They can be thought of as silos of data, or memory.  They can also be bound to view components and this is where the concept of changing the model to change the view works.  This is why they are used as a major part of the Cairngorm framework.  (Lots of people don’t like singletons, and I’m still not entirely sure why)

Here is an example of a Cairngorm singleton : -

package com.worthyashes.simpleCairngorm.model
{
        import com.adobe.cairngorm.model.IModelLocator;
        [Bindable]
        public class MemoryModelLocator implements IModelLocator
        {
         //Singleton code
         private static var _instance:MemoryModelLocator;

         public function MemoryModelLocator(enforcer:SingletonEnforcer)
         {
         if (enforcer == null)
             {
              throw new Error("Like at the end of Highlander, before the crap sequal, there can be only one");
             }
         }

          public static function getInstance():MemoryModelLocator
          {
           if (_instance == null)
            {
                _instance = new MemoryModelLocator(new SingletonEnforcer());
              }
            return _instance;
            }
            //End of singleton code

           //Pop your vars into the model from here on
      }
}
class SingletonEnforcer{}

Lets go through the code

[Bindable]

public class MemoryModelLocator implements IModelLocator

The [Bindable] keyword makes this class available for flex bindings so it is possible to directly bind the ModelLoactor and it’s subsequent variables to the view components as discussed above.

A Cairngorm Singleton is also known as a ModelLoactor and implements the IModelLocator interface. (For a discussion of interfaces you’re going to have to do a bit of a google.  I understand them, understand how and why to use them, but for the life of me I can’t actually put into words why – I’ll have a go at a later post)

Now for the slightly mind bending bit, once you’ve got the hang of this it will all become clear.

private static var _instance:MemoryModelLocator;

This variable _instance, the underscore is there to indicate it is a private variable (the private keyword does that really, the underscore is more a visual reminder in the code), holds a reference to the MemoryModelLocator class.  Which is the class that it is in.  So it holds a reference to itself, in itself.  Which you’d imagine would have another _instance variable, but the keyword static indicates that this variable is always the same in every single instance of this class.  So every time you access the Singleton after it has initially been instantiated you are getting the same class back.  I’ve just re-read that, I think it makes sense – if not then send me a mail and I’ll re-work that paragraph.

Now onto the constructor.  In order for a singleton to work we need to only ever create one at any time.  This means we DON’T want to be able to call the constructor directly, as this would instantiate a new class.  By convention we call a static function called getInstance() (It doesn’t have to be called this, but as it’s a convention I recommend you stick to it) that returns an instance of the class.

Singletons in AS2 were easier to do.  This was because it was allowed to create a class and set the constructor to be private.  So you’d write something like : -

private function MemoryModelLocator()
{
}

However you can’t do this in AS3.  So we have a hack.  The Cairngorm team have acknowledged it as a hack, so I’ll say it too, hack, hack, hack.  To understand how this hack works we need to look at the new package structure of AS3.  In this case : -

package com.worthyashes.simpleCairngorm.model
{
//The class goes in here
}

Now if I put another class in this package (folder) I would be able to instantiate the MemoryModelLocator class without importing it and use the functions within it.  I could create an instance of the class without any bother at all, and we want to stop this.  So we create a class outside the package declaration.

//End of class
}
class SingletonEnforcer{}

This class is outside the curly brackets that close off the package, and is not available to ANY class except for the MemoryModelLocator class.

So if we pop an instance of this Singleton enforcer class into the constructor of the MemoryModelLocator class then we can force the MemoryModelLocator class to only ever be instantiated by itself through the getInstance() function.

So the constructior is : -

public function MemoryModelLocator(enforcer:SingletonEnforcer)
{
if (enforcer == null)
{
throw new Error("Like at the end of Highlander, before the crap sequal, there can be only one");
}
}

and the getInstance() function looks like this.

public static function getInstance():MemoryModelLocator
{
if (_instance == null)
{
_instance = new MemoryModelLocator(new SingletonEnforcer());
}
return _instance;
}

To go through this and explain it, remember that the _instance variable is static and therefore will be the same every time this class is accessed.  What we do with the getInstance() call is to first of all check if the _instance variable exists.  If not then we create it by calling the constructor with an instance of the SingletonEnforcer class.  This can be accessed by the getInstance() function as it is in the MemoryModelLocator class.  Then we return the _instance variable.  So if we make the call to the getInstance() function in the MemoryModelLocator we will ALWAYS get the same Singleton.  As it is a static function (which it has to be so we can call it and return a static variable) we use it slightly differently, like this : -

var model:MemoryModelLocator = MemoryModelLocator.getInstance();

Right – hopefully that all made sense.  It’s a bit confusing, but hopefully once you see the ModelLocator in action it’ll all be made clear!

OK – so they forgot to tell me it was for flash player 8.  Oh well.  So I’ve done it for ActionScript 2 with some controls for testing.

Papervision 3d AS2

Have fun!

OK, not much to write home about, but as a first go I’m quite pleased with myself.

Have a butchers!