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

Contexts for String Strategies
You can think of the context classes as the clients for the strategies. They use the different
strategies. Often, you will hear that a client has-a behavior. Whenever a client
class delegates to a delegate class, such as the strategy classes in Figure 11-4, it has-a
behavior generated by the strategy class. In this application, the context classes represent
the client classes for the strategy classes.
Like all context classes, the StringChecker class in Example 11-21 sets a reference to
the two strategy interfaces, StringWork and SortWork. In addition, it has functions,
workStrings( ) and workSorts( ) that constitute the methods used to delegate work to
the strategies.
Example 11-21. StringChecker.as
package
{
//Context class
class StringChecker
{
protected var stringWork:StringWork;
protected var sortWork:SortWork;
public function StringChecker( ):void
{
}
}
}
public function workStrings(s:String):String
{
return stringWork.stringer(s);
}
public function workSorts(a:Array):Array
{
return sortWork.sorter(a);
}
public function setString(sw:StringWork):void
{
stringWork=sw;
}
public function setSort(sow:SortWork):void
{
sortWork=sow;
}
In addition to having reference properties and methods, the context class includes
setter operations, setString( ) and setSort( ), to dynamically set strategies to
instances of the context classes.
Next, in Examples 11-22 and 11-23, two concrete context classes extend the primary
context class. Note that they inherit the references to the strategies,
416 | Chapter 11: Strategy Pattern