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

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