Repeated string without a loop

A problem comes up

This week I had a relatively simple problem that I needed to solve. Because it was simple and I didn't like the obvious solution, I thought I'd share the solution I came up with.

The problem was this:

• I had a string where each character represented some data as part of a collection of data.
• I had to change these characters out of order (for example: character 196, then 13, then 87, etc)

My approach - Create a string of n-length

The approach I decided on was to start by creating a string of the final length I would need then update each character as I got the information I needed. Should be simple enough to create a string of a certain length but alas, not so simple as to have a String.createStringOfLength() method.

The obvious method

My first method of doing this is the obvious loop method. I'm a big fan of loops so it looked like this:

function createStringOfLength(length:uint):String {
    // we'll use 'x' as our default character - spaces are fine too.
    var output:String = "";
    for(var index:uint = 0; index < length; index++){
         output += "x";
    }
    return output;
}

And that function works fine, it is understandable but it just seems that there should be a more elegant solution.

A more elegant solution

The problem with the method above is that I can't just create a string of an arbitrary length but I feel like I should be able to. Is there something else in AS3 that you can create of an arbitrary length? Yes! You can create a Vector of a specific length and use default values to boot.

Here's where it starts to get elegant. Since Strings really are just an array of characters this correlation makes a lot of sense. The code above can actually be recreated in 2 lines (not counting the function definition and enclosing curly braces).

function createStringOfLength(length:uint):String {
     var output:Vector.<uint> = new Vector.<uint>(count, true);
     return output.join("").replace(/0/g, "x");
}

I used a few tricks of the language here, so some of this may not be obvious. First, in AS3, the default value for a uint is 0. That is the reason I search for it in the pattern for the replace call. Second, and really the main thing, I took advantage of the ability to create a Vector of a specified length and fill it with its type (in this case uint) defaults. Finally, I just used the Vector.join method and replaced the default 0 with whatever character I wanted. Admittedly, I could have just left them all as 0 but the replace step was so simple I thought I'd throw it in.

Conclusion

There probably wasn't a performance reason for me to create this solution, and I honestly don't know if it is any more performant. Looking at new ways to relate to a problem is the bread and butter of a programmer though. So, if you've ever wanted to create a string of a specified length or repeat any string a certain number of times here is a new way to think about the problem.

Do you have another solution? If so, I'd love to hear it. Did you like my solution? Hate it? Have an improvement? Let me know in the comments below or share a link to your code. Github's gists are a great way to share code snippets - as I just did right there.

Function Overloading in AS3

Why doesn't AS3 have function overloading

If there is anything I hate more than when actionscript doesn't do something I wish it would, it is when people complain about something they wish it would do. Sure, it would be nice if it incorporated every programming concept ever but that just isn't going to happen. In fact, this point is the same for every language out there. It sure would be nice if they all did everything but then there would only be syntacticular differences and that would be silly. Anyway, actionscript does not natively offer function overloading, and I've heard and/or read people complain about that from time to time.

Roll your own

Usually the reason you wish a solution existed natively is because you've used it before and you'd like to have the same ease writing the code. At least, if we follow the premise of not pre-optimizing code. So, if a language doesn't have that construct what do you do? Either find an alternate or roll your own. Today we are going to roll our own method for overloading functions in AS3 to allow for some of the benifits of native function overloading.

This isn't my idea

I have to admit, this isn't my idea. Back in the days of AS2, there was one library that did a lot of rolling its own solutions to constructs actionscript didn't provide. That library was as2lib by Simon Wacker and Martin Heidegger. I remember just reading the as2lib source code to learn different ways of doing thing. They had a solution for function overloading that I used as a basis for the AS3 code. I figured, AS3 had better reflection and introspection (as2lib had libraries for that as well) than AS2 so this should be fairly easy. In some ways it was and in some was it wasn't. That's a good thing because I learned a few things along the way.

Enough typing, where's the code

The code I wrote to allow this functionality is available at github. Usual rules apply, this code is just a proof of concept, for educational purposes only. Though I've written some tests, I make no guarantees.

Sample Usage

Sample usage is available in the Main.as file on github but I'll provide you with a taste here.

private function aFunction(... args):* {
    const overloader:Overloader = new Overloader();
    overloader.addHandler([String, Number], onStringNumber);
    overloader.addHandler([String], onString);
    overloader.addHandler([Number], onNumber);
    overloader.addHandler([int], onInt);
    overloader.addHandler([uint], onUint);
    overloader.addHandler([Boolean], onBoolean);
    return overloader.process(args);
}

private function onInt(value:int):void {
    trace("We got int: " + value);
}

private function onUint(value:uint):void {
    trace("We got uint: " + value);
}

private function onBoolean(value:Boolean):void {
    trace("We got Boolean: " + value);
}

private function onNumber(num:Number):void {
    trace("We got number: " + num);
}

private function onString(str:String):void {
    trace("We got string: " + str);
}

private function onStringNumber(str:String, num:Number):void {
    trace("We got string, number: " + str + ", " + num);
}

// then to use the overloaded function
public funciton Main(){
    aFunction("Hello World", 13); // output: We got string, number: Hello World, 13
    aFunction(1 == 0); // output: We got Boolean: false
    aFunction(13); // output: We got uint: 13
    aFunction("Goodbye"); // output: We got string: Goodbye
}

A couple notes and gotchas that you might be wondering about as you look at this code.

• Numerical arguments are automatically converted to any numerical class asked for, as long as the value can be of that type.
  • For this reason I made it test numerical explicitness in the following order: uint before int and int before Number.
    • Therefore if their are two matching functions due to numerical parameters a method using uint will be considered more explicit than a method using int or number.
  • You can't force a numerical type. I tried several methods and none worked.
• If your overloaded function returns void you will need it to return * so it will compile without error.
  • EDIT: not true, just don't use a return statement
• Because AS3 uses method closures most of the time, instead of anonymous functions, you usually don't have to worry about function scope. This is mostly a good thing. Watch out if you do use an anonymous function though. It will most likely work correct but there are a few ways it could fool you.
• I wanted to do introspection on the method signatures so you didn't have to send in the values but, alas, method signatures do not seem to be available via reflection. From what I could figure out from studying the Tamarin code, they are part of the functions Trait object which isn't available from actionscript (and may go away in the future according to the documentation). This means you have to put them in as Arrays.

Not True Overloading

Okay, so this isn't true overloading but it gets us a little of the way there. The only solutions available online use the ellipsis (...) method but you still have to write the boilerplate logic to provide type checking. Also, what happens if there is no match? With my code you at least get an error telling you what went wrong. It isn't compile time but it can help with debugging.

Also, look at what this solution actually provides. It doesn't have to be used for function overloading. It could be used anywhere you want to handle differing types of data passed in as arguments. I could envision this helping to trim down some nasty if and/or switch statements. Take a look and see what it could do for you.

Conclusion

I find the Function class and Function objects fascinating in actionscript. Back when I dug into the different types of Delegate classes for AS2 (I actually made a similar one for AS3 at one time) I learned a lot about the language as a whole. Scope used to be the bane of my existence and then I finally understood it. Scope may not be an issue anymore in AS3 but there is still quite a bit to learned about the language from studying Function objects. The very fact that a Function is an object that can be passed around in actionscript is a very nice thing. Not all languages allow that type of functionality. I guess if you are using those, you'll have to roll your own function passing solution.

Quick tip Ctrl+3

So lately I've been teaching myself how to use the Vim editor. If you know anything about Vim you know it is all about efficiency of keyboard usage. The more I've used Vim, the more I don't want to move my hand to my mouse if I don't have to. It's not that I'm lazy, I just want to challenge myself to be more efficient. If you've been reading my blog lately you may have read about me using embedded fonts via Resource Bundles. One problem I've always had with embedded fonts in Flash Builder is that some builds they work and some they don't. I'm guessing its part of the incremental compilation process because doing a Project-->Clean... seems to fix the problem. It works but then I have to move my hand all the way over to my mouse to make it happen. I needed to find a good keyboard shortcut, for some reason I wanted it to be a default key binding.

Enter CTRL+3

There are shortcuts for Flash Builder common features but Project-->Clean... isn't one of them. Eclipse has an interesting Keyboard Shortcut in CTRL+3 - Quick Access. The Quick Access shortcut allows you to hit the shortcut then just start typing the name of the feature you want to use - and there is a big list available to you in Eclipse. A bonus to the Quick Access shortcut is that the last feature you used can be used by hitting return. So to set up a shortcut for Project-->Clean there are just a couple steps.

1. Hit Ctrl+3
2. type 'Clean...' then press enter

Now you can trigger a Project-->Clean... with just Ctrl+3 and Enter. The default for me is to clean all projects and I usually only have one project open at a time so I just enter through that as well.

Really, you can use this with just about any feature you'd like. Once you use it, the feature goes into your Quick Access list. Then its as easy as an arrow up or down (or a few keystrokes to type the action name) to get the feature back to the top of your list and use it.

For me this is one of the hidden gems of Flash Builder. You get this for free for using Eclipse. There's plenty more where that came from too. Are there some hidden gems you use all the time? Please share them in the comments below. Flash Fridays are all about sharing knowledge with the community so that we become better developers.

Setting up Resource Bundles

In last week's Flash Friday post I wrote about using resource bundles to handle embedded fonts. I also left out any instructions about how to set up your project to use resource bundles, instead telling the reader to search the interwebs. I also said I would provide one of my own instructions so here it is.

Project Setup

Your project needs to be able to find your resource bundles so they need to live in your source path. You could place the bundles in the same folder as your source code, but I find that feels a little disorganized. Instead create a folder for your resource bundles and add it to your source path.

In other tutorials they talk about using resource bundles for localization. If that is the case you can add the files as follows. I'll assume you are using the en_US locale, otherwise replace all instances of en_US with the locale you are using.

1. create folder path in your project of: localeen_US
2. add the source folder locale{locale}
3. add the following to your compiler arguments: -locale=en_US

Now you can place your resource bundles in the localeen_US folder.

Property Files

Resource bundles are sometimes referred to as property files because you create them in files with a .properties extenstion. The part before the extension is the bundle name, and you would use that to get the information you wanted. For example, you you had a bundle named fonts you would create a file called fonts.properties. If you were paying attention to my previous article you probably saw me use this same bundle name.

Inside the property file

The property file is fairly simple. It is just a key/value pair separated by an equal sign(=). A simple resource bundle that stores text strings might be called text.properties and look like the following.

# text.properties

hello=Hello World!
goodbye=Good-bye cruel world!

You can look back at my font embedding article to see how I embedded fonts. You can use the same method to embed anything that you can embed using the Embed metatag.

Using the properties in the file

The first thing you need to do is add the Resource Bundle metatag somewhere in your project. You only need to use it once per project for every bundle you are going to use. However, once you do this it gets compiled into the project, even if you don't use the resources. So I would recommend using it in the class(es) that use(s) the bundle.

	[ResourceBundle("fonts")]
	public class MyFontsBundleUsingClass {
		...

Then to use the resources you just need to get an instance of the ResourceManager use one of its functions to get the resource. Here is an example for grabbing a String from my text.properties file I created earlier.

	var resources:IResourceManager = ResourceManager.getInstance();
	var hello:String = resources.getString("text", "hello");
	var goodbye:String = resources.getString("text", "goodbye");

Of course you can get more than just strings from a property file. Just choose from the following list of functions in the IResourceManager interface.
• getString
• getBoolean
• getInt
• getUint
• getNumber
• getStringArray
• getClass
• getObject

And that is my basic primer on using ResourceBundles in actionscript projects. In the grand tradition of this line of posts I am leaving out many important bits of information. Loading resource bundles at runtime is one of them. I'll leave that as a web search exercise for the reader until I write an article on that in the future. If there are other bits of information you would like clarity on let me know in the comments.

Resource Bundles and Fonts

If you've been working with Flash for a while, especially FlashBuilder, you've probably heard of resource bundles. If you are like me you heard they had something to do with localization. Then you quickly forgot about them. The truth is they aren't only for localization. In fact, they are a really good way to centralize and manage resources in actionscript project. They also happen to work really well for localization. So if they do more than just localization, what are resource bundles.

What are Resource Bundles

I hate to state the obvious, but resource bundles are bundles of...wait for it...resources! So with that the next question is, "What is a resource?"

A resource could be a...
• ...String
• ...Image
• ...Config Value
• ...Font

Why would you want to use them?

Okay, now you know what resources are. You've managed these resources in other ways. Why would you want to use resource bundles over the way you already do?

Here are a few good reasons
• 2 words, cleaner code
• easier localization
• change text, configs, etc. in one spot

How to setup

Before we get into using resource bundles with fonts, it is important to know how to set them up. Also you might want to know how to use them with the other, simpler types of resources. There are many great articles already available online if you want to search. I plan to write a "how to setup resource bundles" post next week so check back then.

I hate fonts (but I understand they make stuff look good)

I have always dreaded working with embedded fonts on a flash project. Even though I've done it many times, and should know how, each project has brought its own wrinkle that has caused grief for me. Embedding fonts via resource bundles gives you more control over the specifics of the font. Also, since it is built into development with the Flex SDK, you can more readily change them for your needs right in the project. Need to embed more characters? Change to/from CFF embedding? Just type in the appropriate text and you are done. Depending on your development environment you may need to clean your project.

One other point, I recently work on a localization project for game that was already live. Even though we had all the text strings externalized this project sucked and was slow going. If I had my strings, and other resources, setup in resource bundles I would have been halfway done with the project before I even started. So enough talk, how can we use resource bundles to help with font embedd?

Embedding fonts with resource bundles

A font gets embedded in a resource bundle much like an image get embedded, using the Embed metatag. In fact it is awfully similar to using the Embed metatag as you would in an actionscript file.

It might look something like this:

#a file called fonts.properties

AFontDesignersLove="ComicSans"
ComicSans=Embed(
	source="./assets/fonts/comic.ttf", 
	fontName="ComicSans", 
	embedAsCFF="false", 
	mimeType="application/x-font", 
	advancedAntiAliasing="true", 
	unicodeRange="U+0020-007E")

The backslash() is useful in property files to make long entries more readable. I'm all about readable, editable code.

To use this font in its current form would work like this:

[ResourceBundle("fonts")]
public class MyFontUsingClass {

// put some other code here

	var resources:IResourceManager = ResourceManager.getInstance();
	var fontName:String = resources.getString("fonts", "AFontDesignersLove");
	var format:TextFormat = new TextFormat(fontName, FONT_SIZE);

	_questionField = new TextField();
	_questionField.defaultTextFormat = format;
	_questionField.embedFonts = true;

// put some more code here

You probably noticed a couple things here:

• I lied - designers hate Comic Sans
• I also put the font name (string resource) in the property file and just used it to bring in the font.

Once you use the resource bundle metatag in your code for a bundle that has fonts, those fonts are already embedded in your code. There is no need to do the old Font.registerFont() silliness. At least not when you compile the resource bundle into your swf.

The above code is still a bit heavy and I'd hate to have to write it every time. My advice is to clean it up into something that looks a bit more like this:

_questionField.defaultTextFormat = Fonts.getFormat();
_questionField.embedFonts = true;

Depending on what type of format data is used, you might need to make this a little more robust than this but aiming towards this will make you enjoy the benefits gained from embedding fonts this way. For now, I leave this as an exercise for the reader. I plan to write an article on some resource bundle good practices* in the future.

Under the mask but I didn't ask - Flash Friday

Masks in the flash IDE are an interesting thing. You may have noticed that masks created in the IDE are not found in the normal "mask" property found on a movieclip. This is because it isn't a normal mask. The mask is working on a layer instead of on a single DisplayObject. This little quirk causes some interesting behavior that you may never have noticed before. If you have a MovieClip with a mask as a top layer of the timeline there is some strange behavior when you addChild to that MovieClip. The added content gets placed under the mask. Wait! What? The added content gets placed under the mask. You may not have noticed this behavior in the past because you may never have done it, you may not have your item cut off by the mask or you just might not have been able to figure out why you couldn't see your item. However, it is happening. [ad#Google Adsense] Another twist on this phenomenon is that if the mask isn't the top layer but your remove the items that are on the top layer then add a DisplayObject. Well, in that scenario your new DisplayObject is also placed under this "Layer Mask". I found this out today when I had a top layer above a mask that was a TextField. For a localization project I'm working on I had to wrap the field in a wrapper class that then gets added back where the textfield was. I was trying to figure out why the textfield was now appearing like it was under the mask. The answer...because it now was.

So how did I deal with this? How can you deal with this if you find it happening? First off, it might be an easy thing to just restructure your timeline so the mask isn't on top. If that isn't possible, the hack easy fix is to add a blank MovieClip symbol to the layer above the mask layer. That is what I did for this asset and all is well.

I haven't extensively tested this but my guess is the quirk may exist if you add something to any layer right above a "Layer Mask" it will placed under the mask. Is this something you have experienced? How have you worked around it? Have you used it for any type of effect?

I don't believe you really want to count on this behavior for anything as I don't believe I've seen it documented anywhere. Someone at Adobe might read my blog :) and decide this isn't appropriate behavior they might fix it in Flash Player 20 or something.

Flash Friday - Version Control

When I first started my Flash Friday posts I wanted to write about the whole flash ecosystem. At the time I thought about Flash, Actionscript, Flex, Flex/FlashBuilder and a few other tools. Recently, I have realized that the ecosystem is much larger than just flash. For people to truly be well rounded flash and actionscript developers who make every other flash and actionscript developer look good its important to know about these non-flash things. One of the most important things to any developer is version control. On the surface, version control seems simple enough. Save files in a way that allows me to go back in time if I make a mistake or forgot what I did in the past. Many people, a past version of myself included, think that's all there is to version control and thus us backup folders or file naming conventions to achieve this goal. I am writing this article because version control is way more than just this and definitely more important. For those who really master it you can actually save yourself quite a bit of time.

Why learn version control

If version control is more than backing up files what is it? I'm glad you asked. Version control is a way to safely and elegantly work with multiple people on a project. The multiple people include people in the same office or people on the other side of the world. It also includes the multiple yous that you wish you could create so that you could finish that cool new feature but you just can't take the time to hunker down and get it done all at once.

Version control is and/or allows:

• Saving a history of your work as it evolves
• Keeping track of who did what
• Trying things out that you might throw away
  • Without breaking working code
  • Keeping a history of that as well
• Working on a file without worrying if somebody else is
• Taking someone else's work in a different direction ( forking )

What should you learn

• SVN - The most popular centralized version control system
  • Lots of great tools makes it easier to include artists in the version control system
• GIT - A very popular up and coming distrubuted version control system
• Branching and Merging
  • Become a master at this for whichever version control systems you learn and it will make your professional life much simpler.

Tools

• Subclipse - a great eclipse SVN plugin you can use with Flashbuilder or FDT
• EGit - a similar eclipse plugin for Git
• TortoiseSVN/TortoiseGit  - two great sell extensions for version control in Windows explorer.
• GitHub - If you are working with Git this is a great place to start putting your code. Lots of straightforward how-tos
• Books - I've found the following two books to be extremely helpful in learning SVN and Git
  • Pragmatic Version Control: Using Subversion
  • Pragmatic Version Control: Using Git

Final Notes

I mentioned SVN and GIT because they are currently in such wide use. However, version control concepts can be learned from any version control system. If your company or project is using something else, such as CVS or Mercurial, learn it and master as much of it as you can. I can't stress enough how important it is to master branching and merging. Get good at this and task switching will be much easier so you'll be able to working on many projects at once.

What are your thoughts on version control? What problems have you had? What successes have you had?

Flash Friday - A Simple List

A few people who've worked with me in a programming job may have heard me talk about how a custom list should be done. For performance reasons you don't want to recreate the visual "cell" n-times. That could lead to all sorts of unforeseen problems. Instead you want only enough cells to be visual during scrolling and as you scroll through the list just bring the "cells" round to the other side. One of the people I work with, Alec McEachran, wrote a blog post  on just this topic. It is entitled "A Simple List" and I'll let you read his article and code on the subject. What is interesting about his code  for a list is he does a great job keeping the list class very simple. It keeps to a pretty narrow responsibility. He's quite good at solutions with well defined class responsibilities.

In our current project, Monster Galaxy, we have used this code in a few places. It has been modified for our purposes but at the base level described in his article the code makes custom list designs easy to implement.

Alec is a very intelligent programmer and has some other great articles on his blog. If you like what you read there you might also like to follow him on twitter (@alecmce). Of course, his twitter feed carries a lot more of his opinions and personality. It's quite fun though, I promise ;)

Of course, I have a blog as well which you are reading now and thank you for that. If you haven't done so already, follow me on twitter( @diacre ) to find out about new blog posts as well as my opinions and personality ( which you may or may not find as colorful as Alec's ). Please let me know in the comments what you think of Alec's list class. If you have a different solution that you like I'd love to hear that as well. Until next time...au revoir.

Flash Friday Refactored - IS_IN

A while back I wrote a proof of concept isIn functionality injector that seemed to work fairly decently. I even wrote some tests for it that it passed with flying colors. Being a proof of concept I never really used it and never ran into the danger of using that functionality. Recently I downloaded the trial for FDT and since it doesn't have the same type of FlexUnit integration that FlashBuilder 4 has I had to get my tests working differently. When I got the tests up an running my tests for the isIn functionality blew up in spectacular fashion. They didn't just fail, the took the whole unit test display down with them. This was the same class and tests that passed cleanly before. What happened?

It turns out messing with the prototype of Object to solve a problem is like fighting fire with a nuclear explosion. It will probably work but cause serious problems throughout the system. So, following the test driven development methodology of red, green, refactor I saw that it was a time for a refactor. Well that and it was now a red test that I wanted to make green.

I came up with a solution that I think is better. It is more flexible than before, since you can select the class you want to add the functionality to. Even better, you can remove the functionality after you add it. Since I've begun to move my code over to GitHub you can find the new code over at https://github.com/darylducharme/Ducharme-Media-Code/tree/master/src/cc/ducharme/utils. The new test class is available at https://github.com/darylducharme/Ducharme-Media-Code/blob/master/test-src/utils/IsInTests.as

You may notice that the last test - dictionaryEnumerationTest()  at this time - is new. This is the test that checks the problem that I found that was not being tested before. If you are writing tests and find a hole in your tests later, it is always recommended to add new tests to keep you from having the same problem in the future.

Hopefully, someone out there can learn from my mistakes on this occasion. Also, the new isIn class and its static functions are a whole lot more useful than what I had written before. Perhaps someone out there can put it to good use.  What do you think?

Flash Friday - Robotlegs Context

A few weeks back I wrote an article saying that I was just starting to work with AS3 Signals and the Robotlegs framework at my new job. Since then I have written a post about AS3 Signals and now it is time to write about Robotlegs. Since there is so much to write about with regards to Robotlegs I had to break out one chunk to discuss.

In working with the framework, reading lots of documentation and finding it central in the diagram above, I thought it best to start with the Context class in the Robotlegs framework.

Robotlegs is an MVCS framework similar to Pure MVC that relies on metadata based dependency injection. On the surface the first cool thing is that you can use the Inject metatag to populate class fields automagically. More automagic part of the framework is that mediators automatically get created when the view they are mediating gets added to the stage. Finally it has a very elegant central event dispatcher and Command pattern model that you barely need to do anything to get working. All this is possible because of the Context.

Getting [Inject] to work

// It really is just this easy
[Inject] public var obj:MyClass;

Most of the power of Robotlegs comes from the use of the Inject metatags letting the framework. However, the framework can't inject anything until it knows what to inject. This is almost entirely done in the Context and I am going to go through the main functions here. Keep in mind that all these methods also have their inverses to undo these acts but I'll let you look those up on your own. For now I'll keep it simple and we can get to more advanced usages in other articles.

Injector methods

injector.mapValue is used when you already have a class instantiated and you want to use that object as a singleton in this application context. The basic format is: injector.mapValue(whenAskedFor:Class, useValue:Object) and might look like this:

var myObject:MyClass = new MyClass();
injector.mapValue( MyClass, myObject );

If you want to do something similar without first instantiating the object, you can use mapSingleton. The format for that is: injector.mapSingleton( whenAskedFor:Class ) and the above example would be changed to this.

injector.mapSingleton( MyClass );

injector.mapClass is used when you want the injector to create a new instance of a class every time it is asked to inject that class somewhere. The format for this function is injector.mapClass( whenAskedFor:Class, instantiateClass:Class ) and if we decided against using a singleton for MyClass instances the above examples would become:

injector.mapClass( MyClass, MyClass );

That last one may seem wierd because you type MyClass twice. However, this is because you could pass in any class that extends MyClass for the instantiateClass parameter ( or implements it if it were an interface ).

Once you've used one of these 3 commands ( or some of the others I can talk about at another time ) on all the values you want to inject in your application, anytime the framework creates or manages a class object it will have the information it needs to do just that. So how do you go about getting Robotlegs to create a class object? Automagic mediators are a perfect example.

Automagic Mediators

In Pure MVC like architectures the Mediator classes handle communication between their views and the rest of the application. Since Robotlegs is an MVCS framework based on Pure MVC this is a perfect opportunity to have the framework create the mediator for you. From the Context class you only have to write something similar to:

mediatorMap.mapView( MyView, MyViewMediator );

In this MyView is a view class and MyViewMediator is the mediator designed for it. Now the application will automagically create a MyViewMediator object when any MyView object is added to the stage and inject a reference to the MyView object into it. It will also destroy the MyViewMediator object just as magically when the MyView object gets removed from the stage. I can write much more about this in an article on the Mediator/View relationship that I plan to write in the near future.

Since Robotlegs creates the mediator it can easily inject what it needs to after it creates the class. Another class type that Robotlegs creates are Command classes.

Events, Commands and tying it all together

Robotlegs uses a centralized event dispatcher throughout to keep the model, view, controller and service sections decoupled from each other and yet tying them together at the same time. One major part of the centralized dispatcher is triggering Commands. If you've read this far, I thank you and I'm guessing you already know about the Command pattern.

To set up the command pattern in the your Robotlegs Context class just use the following format. commandMap.mapEvent( eventType:String, commandClass:Class ) which might look like this:

commandMap.mapEvent( MyCustomEvent.SOMETHING_IMPORTANT, DoSomethingImportantCommand );

Now, whenever a class in the framework dispatches the SOMETHING_IMPORTANT custom event the DoSomethingImportantCommand will be created and executed. As a bonus, the specific instance of MyCustomEvent can be injected into the command with a single line:

[Inject] public var event:MyCustomEvent;

Conclusion

So this article did not have had any sexy embedded SWF files that use Robotlegs. However, this framework's strength is not about sexy SWF files but its ease of use which should make creating that sexy file go quicker. The context file is the heart of Robotlegs and using the few methods I've written about here you can use it to make a fairly robust application linked together with dependency injection.

I've purposely left a lot out of this post. This is because I just want to wet your appetite to give it a shot as well. Also, I'd like to hear what kind of questions come up for you in the comments. Finally, I could write a lot more just about the context class and favoring configuration over convention( well sort of  ), but it would just turn into a mess of words and I'd be surprised if you read this far anyway. If you did, thank you. I'd love to hear what you think of Robotlegs if you've tried it out or even if you've decided not to.