实现Square类，让其继承自Rectangle类，并在Square类增添新属性和方法

1 #import <Foundation/Foundation.h>
2
3 @interface Rectangle : NSObject{
4     int width;
5     int height;
6 }
7 @property int width,height;
8 -(int) area;
9 -(int) perimeter;
10 -(void)setWidth:(int)w andHeight:(int)h;
11
12 @end
13
14
15 #import "Rectangle.h"
16
17 @implementation Rectangle
18 @synthesize width,height;
19 -(void)setWidth:(int)w andHeight:(int) h{
20     width=w;
21     height=h;
22 }
23 -(int) area{
24     return width*height;
25 }
26 -(int) perimeter{
27     return (width+height)*2;
28 }
29
30 @end
31
32
33
34 #import <Foundation/Foundation.h>
35 #import "Rectangle.h"
36 @interface Square : Rectangle
37 -(void) setSide:(int) s;
38 -(int)side;
39 -(int)area;
40 -(int)perimeter;
41
42 @end
43
44
45 #import "Square.h"
46
47 @implementation Square
48
49 -(void) setSide:(int) s{
50     [self setWidth:s andHeight:s];
51 }
52
53 -(int) side{
54     return width;
55 }
56
57 -(int)area{
58     return width*width;
59 }
60
61 -(int)perimeter{
62     return 2*(width+height);
63 }
64 @end