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

Example 5-11. CarAdapter.as (continued)
}
}
The CarAdapter class implements the ICar interface and has a parameterized constructor
that receives a LegacyCar instance. It contains four public methods as specified
in the interface. All four methods use one of the public methods in the LegacyCar
class for implementation. The steering angle is set in discrete steps of 50 degrees, as
discussed previously. Note the nSteeringAngle property that keeps track of the current
steering angle of the car. Adapter classes can have their own properties and
methods to support implementation.
The Client
public function CarAdapter(car:LegacyCar)
{
this.legacyCar = car;
this.nSteeringAngle = 0;
this.goStraight( );
}
public function start( ):void
{
legacyCar.start( );
}
public function turnMoreToTheLeft( ):void
{
legacyCar.setSteeringWheelAngle(nSteeringAngle -= 50);
}
public function turnMoreToTheRight( ):void
{
legacyCar.setSteeringWheelAngle(nSteeringAngle += 50);
}
public function goStraight( ):void
{
legacyCar.setSteeringWheelAngle(nSteeringAngle = 0);
}
All that’s left to accomplish is to develop a client to test the adapter. The client
(Main.as shown in Example 5-12) creates a new instance of LegacyCar and passes
two parameters to the constructor that places it on the center of the stage. Next, it
creates an instance of CarAdapter and passes the previously created LegacyCar
instance to it. The client also has to receive input from the keyboard to steer the car.
To do this, the client attaches the onKeyPress( ) listener function to respond to key
down events. This listener function calls appropriate methods on the adapter class
based on keyboard input. The onKeyPress( ) listener function responds to the left,
Example: Car Steering Adapter | 191