Quickly Build a Frame-by-Frame Game - Beginning iOS6 Games Development - page 105

In Listing 5-7, we see the header file for the class Actor02 . There are five properties that represent
the basic attributes required for this example. The property actorId is used to identify the actor;
we will see how we use this to map each Actor02 to an UIImageView . The property center tells us
the location of each Actor02 . The property speed indicates how fast this actor moves. The property
radius represents the size of this actor. Finally, the property imageName describes how this actor
should be drawn on the screen.
The type of the property center is CGPoint . Strictly speaking, we will not be directly using this
CGPoint to set the location of a UIView or other Core Graphics component. But CGPoint is a simple
way to wrap an X and Y value, and we are already familiar with it. For this example, it makes little
difference if we use CGPoint or a struct of our creation to represent a point. However, if you wanted
to make sure your code was not dependent on Core Graphics in any way, you would want to define
your own type for representing a point.
Also of note in Listing 5-7 is that an Actor02 does not have a width or height, just a radius . This
is done to simplify the example, and also because many games require only a single dimension
to describe the size of an actor. If you build your own game framework, you may choose to have
your actors include a width and height—it really depends on the game. Certainly if you look at
prebuilt game engines you will find that their base type has all sorts of features you may or may
not use. It may make a lot of sense to use a game engine, but here we are trading complexity for
understanding.
A Simple Actor
Listing 5-7 shows that the Actor02 has three tasks defined. Listing 5-8 shows the implementation of
these tasks.
Listing 5-8. Actor02.m
#import "Actor02.h"
@implementation Actor02
@synthesize actorId;
@synthesize center;
@synthesize speed;
@synthesize radius;
@synthesize imageName;
-(id)initAt:(CGPoint)aPoint WithRadius:(float)aRadius AndImage:(NSString*)anImageName{
self = [super init];
if (self != nil){
[self setActorId:[NSNumber numberWithLong:nextId++]];
[self setCenter:aPoint];
[self setRadius:aRadius];
[self setImageName:anImageName];
}
return self;
}
-(void)step:(Example02Controller*)controller{
//implemented by subclasses.
}