Actually, a constructor method is automatically included if none is specified in ActionScript 3.0. However, a constructor method is only needed to be specified if you are going to have the instantiating object do something other than serve as a platform for using the methods and properties of the instantiated class.

I’ve been having better luck asking myself, Do you really need a constructor function? rather than Why did I leave (an explicit) constructor function out?

Kindest regards,
Bill

I did note:

The DataProvider object can be loaded with data in several ways—using the addItem() method, an array or XML files.

So, you can use XML files with this design. As with most examples in this blog, we use pretty simple examples with the focus on the architecture and not the size of the task at hand. In that sense, all of the examples are ‘over-designed.’ No disagreement there. The important feature of the designs is whether they can be easily changed without causing a chain reaction the cripples the program.

Given that, let’s put this design to the acid test. Add a concrete Product class (DataSupply is the Product class in this example; so it would be an extension of DataSupply) that pulls data out of an XML file but still places the data into the DataProvider object that can be used with the program.

Thanks for your insights and let’s see that new DataSupply subclass that incorporates your idea!

Kindest regards,
Bill

The example is pretty good as usual! I really like to see Patterns in Action. The point of the post was quite clear.

Now, looking trought a different perspective, I think this is the classical example of an over-design situation, IMHO.

A XML parser/logic/algorithm would be quicker, easier and could easily be encapsulated.

Don´t miss understand me. I´m just raising the importance of not to over-design a simple application.

Cheers

I am very glad to hear that. When I get to the State pattern, I decided to create it as a simple progressive download player because not that many have Flash Media Server.

Kindest regards,
Bill