实现Square类，让其继承自Rectangle类，并在Square类增添新属性和方法，在2的基础上，在Square类中重写Rectangle类中的初始化和打印方法
#import <Foundation/Foundation.h>
@interface Rectangle : NSObject{
int width;
int height;
}
@property int width,height;
-(int) area;
-(int) perimeter;
-(void)setWidth:(int)w andHeight:(int)h;
-(void)print;
@end
#import <Foundation/Foundation.h>
@interface Rectangle : NSObject{
int width;
int height;
}
@property int width,height;
-(int) area;
-(int) perimeter;
-(void)setWidth:(int)w andHeight:(int)h;
-(void)print;
@end
#import <Foundation/Foundation.h>
#import "Rectangle.h"
@interface Square : Rectangle
-(void) setSide:(int) s;
-(int)side;
-(int)area;
-(int)perimeter;
-(void)print;
@en
#import "Square.h"
@implementation Square
-(void) setSide:(int) s{
[self setWidth:s andHeight:s];
}
-(int) side{
return width;
}
-(int)area{
return width*width;
}
-(int)perimeter{
return *(width+height);
}
-(void) print{
NSLog(@"side width: %d",width);
}
@end