Create Your Characters: Game Engine, Image Actors, and Behaviors - Beginning iOS6 Games Development - page 140

Here you can see the updateScene task as defined in the class Example01Controller. The class
Example01Controller extends GameController so it inherits the game engine logic defined in that
class. The updateScene task simply adds a new power-up every 5 seconds and then calls the super-
implementation of updateScene . The header file for the class Powerup is shown in Listing 6-12.
Listing 6-12. Powerup.h
#import <Foundation/Foundation.h>
#import "Actor.h"
#import "ImageRepresentation.h"
#import "ExpireAfterTime.h"
enum{
STATE_GLOW = 0,
STATE_NO_GLOW,
PWR_STATE_COUNT
};
enum{
VARIATION_HEALTH = 0,
VARIATION_CASH,
VARIATION_DAMAGE,
PWR_VARIATION_COUNT
};
@interface Powerup : Actor <ImageRepresentationDelegate,ExpireAfterTimeDelegate>{
}
+(id)powerup:(GameController*)aController;
@end
This header file starts by defining two enumerations. The first enumeration defines the values for the
two states of Powerup , STATE_GLOW or STATE_NO_GLOW. The second enumeration defines the
values for the three variations of Powerup . Both of these enumerations end with a value that has
the word COUNT in it. For those developers who are not coming from a C background, this is an
old trick used to create a constant for the number of items in an enumeration. For example, in the
first enumeration, STATE_GLOW has a value of 0, so STATE_NO_GLOW has a value of 1. This gives
PWR_STATE_COUNT a value of 2, which is the number of states there are. Clever, no?
The class Powerup as defined in Listing 6-12 extends Actor . It also conforms to the protocols
ImageRepresentationDelegate and ExpireAfterTimeDelegate . We will look at the tasks that come
with these protocols when we look at the details of the ImageRepresentation and ExpireAfterTime .
The only new task defined for the Powerup class is the constructor powerup :. Let's take a look at that
task in Listing 6-13.