通过继承来扩展

main.m

#import <Foundation/Foundation.h>

#import "Rectangle.h"

int main(int argc, constchar * argv[]) {

 

    @autoreleasepool {

        Rectangle *myRect = [Rectanglenew];

        XYPoint *myPoint = [XYPointnew]; 

        myRect.width = 5;

        myRect.height = 8;

        //[myRect setWidth:5 andHeight:8];

        //[myPoint setX:10 andY:200];

 

        myPoint.x = 10;

        myPoint.y = 200;

 

        myRect.origin = myPoint;

        NSLog(@"Rectangle w = %i, h = %i",myRect.width,myRect.height);

        NSLog(@"Origin at (%i, %i)",myRect.origin.x,myRect.origin.y);

        NSLog(@"Area = %i, Perimeter = %i",[myRect area],[myRect perimeter]); 

    }

    return 0;

}

                                                                                                              

 

Rectangle.h

 

#import <Foundation/Foundation.h>

#import "XYPoint.h"

 

@interface Rectangle : NSObject               

//rectangle 矩形                                              

//origin    原点                                             

//perimeter 周长

 

@propertyint width, height;

//-(void)setWidth:(int) w andHeight: (int) h;

-(int)area;

-(int)perimeter;

//origin的setter和getter方法

-(XYPoint *) origin;

-(void) setOrigin: (XYPoint *) pt;

@end

 

 

Rectangle.m

 

#import "Rectangle.h"

@implementation Rectangle

{

    XYPoint *origin;                         // 原点

}

 

@synthesize width, height;

 

                                            //-(void)setWidth:(int) w andHeight: (int) h{

                                            //

                                            //    width = w;

                                            //    height = h;

                                            //}

-(int)area{

    

    returnwidth * height;

}

-(int)perimeter{

    

    return  (width + height) * 2;

}

 

                                            // 添加方法    origin的steetr方法和getter方法

 

 

-(void) setOrigin: (XYPoint *) pt{

    

    origin = pt;

}

 

-(XYPoint *)origin{

    

    returnorigin;

}

 

 

@end

 

 

XYPoint.h

 

#import <Foundation/Foundation.h>

@interface XYPoint : NSObject

 

 

@propertyint x, y;

 

//-(void) setX:(int) xval andY: (int) yval;

 

 

@end

 

 

XYPoint.m

 

#import "XYPoint.h"

@implementation XYPoint

 

@synthesize x, y;

 

//-(void) setX:(int) xval andY: (int) yval{

//    

//    x = xval;

//    y = yval;

//}

@end