ActionScript 3.0 Design Patterns.pdf - VideoTutorials-bg.com

Example 3-10. Alert.as
}
}
{
Alert._instance=new Alert(new PrivateClass( ));
trace("Alert instantiated");
}
return Alert._instance;
}
//Alert Property
public var colorFont:uint;
//Alert Methods
public function getMsg( ):String
{
return _msg;
}
public function setMsg(alert:String):void
{
_msg = alert;
}
class PrivateClass
{
public function PrivateClass( ) {
trace("PrivateClass called");
}
}
Save the file as Alert.as. As you can see, this Singleton design pattern doesn’t have to
be saved as “Singleton,” and the only reason that name was used in the previous
examples was to help you better see its structure, and where it belonged in the application.
In fact, it’s almost identical to the other Singleton.as files used as examples in
this chapter, and even has the same methods as in Example 3-8. However, this example
includes a property used as a variable in the font color of the text field used here.
Conceivably, your application may need different colored messages to differentiate
categories of advisements your application might employ.
In ActionScript 3.0, you can create a TextField instance in one of two ways. First,
you can create it dynamically in the script, as we will do in this example. Alternatively,
you can create a MovieClip object on the stage, embed a TextField in the
movie clip, and then reference the embedded TextField. Unless you have a good reason
for doing so, it’s more practical and uses less memory to just write the script for
the TextField. (Further on in this chapter, a movie clip in the shape of a shopping
cart with an embedded text field shows how to create and dynamically use a
TextField object on the stage.)
Open a new ActionScript file and after entering the code in Example 3-11, name the
file AlertText.as and save it in the same folder as Alert.as.
114 | Chapter 3: Singleton Pattern