Polymorphism can be found in the Strategy classes themselves—they are written so that depending on the context of their use, they will have different meanings. I believe that we did type to the interface and not the implementation.

Kindest regards,
Bill

For example in the client…

protected var _context:IContext;

protected function init():void{
_context = new ConcreteContext(”someUrl.swf”);
}

Wow! You sure can pick the topics! Object pooling in design patterns is fairly controversial, but I agree it would be a good topic–just to see what the pros and cons are.

In some respects, we all want more speed, but with the speed of current memory and CPUs, it’s not the issue it once was with the old 8-bit processors and severely limited memory. Instead, the issue of speed has shifted to design and re-design. However, I’m a sucker for squeezing more speed from a program (as the Flyweight patterns does) and it is something that I think is worth a post. However, here’s a list of what I have to cover first:

Deal with my client’s project
Finish re-writing a video player
Posts on the following topics:
    Open/Closed Principle
    Dependency Inversion Principle
    Least Knowledge Principle
    Hollywood Principle
    One reason to change principle
    Part II of Builder Pattern

Possibly Chandima might be interested and we could have something sooner, but until I get these other projects off my desk, I can’t put anything new there. However, it is a perfect topic for this blog. (Maybe you’d like to write a post on it?)

Thanks for the great idea,
Bill

Jiri

In your code just type in the symbols as you always do. Your code was fine. I just added the <pre> tags to format it–never use the UTF-8 code in your programs.

A lot of developers (myself included) have used multiple Context classes–an abstract base class and multiple concrete implementations. However, I’ve been going the other way–towards a single concrete Context class.

I suppose either way works. Anyway, the question to ask with design patterns is, what will happen if I make changes? As long as you can keep the relations loose and functional, you will find many variations that you can work with.

Thanks for all your interest and very nice work.

Kindest regards,
Bill

Thank you

Curro

I have re-written the interface and added a getContent():* function.
Here is the new ILoadMaster class:

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package 
{
	import flash.display.Sprite;
	import flash.errors.IllegalOperationError;
 
	//Abstract class: Strategy Interface
 
	public class ILoadMaster extends Sprite
	{
		public function loadStuff(url:String):void
		{
			throw new IllegalOperationError("Abstract method: must be overridden in a subclass");
		}
		public function getContent():*
		{
			throw new IllegalOperationError("Abstract method: must be overridden in a subclass");
		}
	}
}

I have also modified the Context class:

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package 
{
	import flash.display.Sprite;
	import flash.errors.IllegalOperationError;
 
	public class Context extends Sprite
	{
		protected var lm:ILoadMaster;
 
		public function Context(lm:ILoadMaster):void
		{
			this.lm = lm;
		}
 
		public function doLoad(url:String):void
		{
			throw new IllegalOperationError("Abstract method: must be overridden in a subclass");
		}
	}
}

I had to add two new Context subclasses: PixContext and TextContext
PixContext is just a copy of the old Context class:

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package 
{
	import flash.display.Sprite;
 
	public class PixContext extends Context
	{
		public function PixContext(lm:ILoadMaster):void
		{
			super(lm);
		}
 
		override public function doLoad(url:String):void
		{
			lm.loadStuff(url);
			addChild(lm);
		}
	}
}

For TextContext I have found a not very elegant solution but it works:

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package 
{
	import flash.display.Sprite;
	import flash.text.TextFormat;
	import fl.controls.TextArea;
	import flash.events.Event;
	import flash.net.URLLoader;
 
	public class TextContext extends Context
	{
		var textA:TextArea;
		var loaderRef:URLLoader;
 
		public function TextContext(lm:ILoadMaster):void
		{
			super(lm);
		}
 
		override public function doLoad(url:String):void
		{
 
			var theFormat:TextFormat = new TextFormat();
			theFormat.size = 16;
 
			textA = new TextArea();
			textA.editable = false;
			textA.focusEnabled = false;
			textA.width = 500;
			textA.height = 300;
			textA.x = 100;
 
			lm.loadStuff(url);
			loaderRef = lm.getContent();
			loaderRef.addEventListener(Event.COMPLETE,textLoaded);
			textA.setStyle("textFormat", theFormat);
			addChild(textA);
		}
 
		private function textLoaded(event:Event)
		{
			textA.text  = loaderRef.data;
		}
 
	}
}

Then of course I had to modify the TextLoader class:

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package 
{
	import flash.net.URLRequest;
	import flash.net.URLLoader;
	import flash.events.Event;
 
	public class TextLoader extends ILoadMaster
	{
		private var urlReq:URLRequest;
		private var loader:URLLoader;
 
		override public function loadStuff(url:String):void
		{
			urlReq = new URLRequest(url);
			loader=new URLLoader();
			loader.load(urlReq);
		}
 
		override public function getContent():*
		{
			return loader;
		}		
	}
}

PixLoader stays just the same. It doesn’t even need to use the getContent method:

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package 
{
	import flash.net.URLRequest;
	import flash.display.Loader;
 
	class PixLoader extends ILoadMaster
	{
		private var urlReq:URLRequest;
		private var loader:Loader;
 
		override public function loadStuff(url:String):void
		{
			urlReq = new URLRequest(url);
			loader=new Loader();
			loader.load(urlReq);
			addChild(loader);
		}
	}
}

Finally I changed the method seeNow in the Client class:

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		private function seeNow(e:ListEvent):void
		{
			var toLoad:String = e.item.data.substr(e.item.data.length - 3);
			container.removeChildAt(0);
			switch(toLoad)
			{
				case "txt":
					contextDy = new TextContext(new TextLoader());
					swf = "../text/" + e.item.data;
				break;
 
				default:
					contextDy = new PixContext(new PixLoader());
					swf="../swf/"+e.item.data;
			}
 
			contextDy.doLoad(swf);
			container.addChildAt(contextDy,0);
			container.x=180,container.y=70;
 
		}

Of course, the first context var in the Client class has to be changed to :

private var context:Context=new PixContext(new PixLoader());

I am not sure all this is better than the old TextLoader class instantiating a text area. What do you think? For me it is, at least, more complicated.

Regards
Curro

You format text just like HTML. However for listings use:

<pre lang=”actionscript” >
–code here–
</pre>

Also I have to use UTF-8 character codes for things like < and >

Take care,
Bill

The same happens with your version: the getContainer function returns a display object and you cannot turn a text file into a display object unless you put it inside one.

Unlike the Loader class, the URLLoader class is not a display object and you do need a URLLoader object to load a text file. If you try to load it with the Loader class you get a IOErrorEvent 2044.

It occurs to me right now that we could have getContainer return a “*” type and then have a concrete TextContext class to instantiate the textfields, textareas or whatever and deal with the incoming data. I don’t know how to do this myself but I think I will give the idea a try.

Well, I think this discussion is really interesting and instructive.
Thank you Jiri and Bill for your help.

Curro

BTW: how can you format the text in this blog?