Accessor Methods

[Arcadiu]

I am stuck in this book I am reading and its about accessor methods and the reason I am here is because I don't understand the code because the author doesn't explain it very well.

All I am asking is just some notes beside each line telling me what is happening in all this code

@interface Car : NSObject 
{ 
    Engine *engine; 
    Tire *tires[4]; 
} 
- (Engine *) engine; 
- (void) setEngine: (Engine *) newEngine; 
- (Tire *) tireAtIndex: (int) index; 
- (void) setTire: (Tire *) tire 
         atIndex: (int) index; 
- (void) print; 
@end // Car

@implementation Engine
- (Engine *) engine 
{ 
    return (engine); 
} // engine 
- (void) setEngine: (Engine *) newEngine 
{ 
    engine = newEngine; 
} // setEngine

Engine *engine = [Engine new]; 
[car setEngine: engine]; 
NSLog (@"the car's engine is %@", [car engine]);

- (void) setTire: (Tire *) tire 
         atIndex: (int) index; 
- (Tire *) tireAtIndex: (int) index;

@implementation Tire
- (void) setTire: (Tire *) tire 
          atIndex: (int) index 
{ 
    if (index < 0 || index > 3) { 
        NSLog (@"bad index (%d) in setTire:atIndex:", 
               index); 
        exit (1); 
    } 
    tires[index] = tire; 
} // setTire:atIndex: 
- (Tire *) tireAtIndex: (int) index
{
    if (index < 0 || index > 3) { 
        NSLog (@"bad index (%d) in "tireAtIndex:", 
               index); 
        exit (1); 
    } 
    return (tires[index]); 
} // tireAtIndex:

Tire *tire = [Tire new]; 
        
    [car setTire: tire 
         atIndex: 2]; 
    NSLog (@"tire number two is %@", 
           [car tireAtIndex: 2]);

I know this is a lot of code but I am really stuck.

If this is not needed in iPhone Dev PLEASE tell me Thanks

Arc