Parent Class: GraphicObject

@interface Circle : GraphicObject

- (void) setRadius: (int) r; - (void) setCenter: (XYPoint *) c; - (int) radius; - (XYPoint *) center; - (int) circumference; - (int) area;

@end

#import "Circle.h" #import "XYPoint.h"

@implementation Circle {     int radius;     XYPoint *center; }

- (void) setRadius: (int) r {     radius = r; }

- (int) radius {     return radius; }

- (void) setCenter: (XYPoint *) c {     if (!center)         center = [[XYPoint alloc] init];    

    center.x = c.x;     center.y = c.y; }

- (XYPoint *) center {     return center; }

- (int) circumference {     return 2 * 3.1416 * radius; }

- (int) area {     return 3.1416 * radius * radius; }

Parent Class: Graphic Object.

Prereq: XYPoint.

#import "GraphicObject.h" #import "XYPoint.h"

@interface Triangle : GraphicObject

@end 

#import "Triangle.h" #import "XYPoint.h"

@implementation Triangle {     int side;     int altitude;     XYPoint *center; }

- (void) setSide: (int) s {     side = s; }

- (int) side {     return side; }

- (void) setAltitude: (int) a {     altitude = a; }

- (int) altitude {     return altitude; }

- (void) setCenter: (XYPoint *) c; {     if (!center)         center = [[XYPoint alloc] init];

    center.x = c.x;     center.y = c.y; }

- (XYPoint *) center {     return center; }

- (int) perimeter {     return side * 3; }

- (int) area {     return side * altitude / 2; }

Subclasses: Circle, Rectangle, Triangle.

@interface GraphicObject : NSObject

- (void) setFillColor: (int) i; - (int) fillColor; - (void) setFilled: (BOOL) b; - (BOOL) filled; - (void) setLineColor: (int) i; - (int) lineColor;

@end 

#import "GraphicObject.h"

@implementation GraphicObject {

    int fillColor;     BOOL filled;     int lineColor; }

- (void) setFillColor: (int) i {     fillColor = i; }

- (int) fillColor {     return fillColor; }

- (void) setFilled: (BOOL) b {     filled = b; }

- (BOOL) filled {     return filled; }

- (void) setLineColor: (int) i {     lineColor = i; }

- (int) lineColor {     return lineColor; }