Employing Flexibility in the Template Method | 343In both concrete classes, atrace( )statement indicates which class is instantiated so
that you can see it in the output. More importantly, each of the two concrete classes
adds unique details to the two abstract operations, doDesign( ) and
determineSupplies( ). Neither includes anything regarding thestoreTools( )func-
tion. BecausestoreTools( )is invariant in all implementations, there’s no reason to
include it. It’s inherited from theShedMaker class.
To test it, both concrete classes are instantiated in the same testing class,BuildShed.
Example 9-7 shows that the two different instances use the interface data type to
instantiate thewoodandsteelinstances. Save the file using the example caption
name in the same directory as Examples 9-4 to 9-6.
Example 9-6. SteelShed.as
package
{
class SteelShed extends ShedMaker
{
trace("SteelShed");
override protected function doDesign( ):void
{
trace("Designing Steel Shed");
}
override protected function determineSupplies( ):void
{
trace("Ok I'll need some corregated sheet metal.")
trace("Better get some steel fasteners too.");
}
}
}
Example 9-7. BuildShed.as
package
{
import flash.display.Sprite;
public class BuildShed extends Sprite
{
public function BuildShed( )
{
//Make a steel shed
var steel:ShedMaker=new SteelShed( );
steel.templateMethod( );
//Make a wood shed
var wood:ShedMaker=new WoodShed( );
wood.templateMethod( );
}
}
}