为MYPoint类写一个分类

#import <Foundation/Foundation.h>
//xieyi
@protocol showOn
@required 
-(void)printOn;
@end
// lei
@interface MyPoint : NSObject<showOn,NSCopying>{
    int x;
    int y;
}
@property (nonatomic,assign)int x,y;
-(id)initWithX:(int)_x andY:(int)_y;
@end
// leibie fenlei
@interface MyPoint(MoveSet)

-(void)moveToX:(int)_x andY:(int)_y;

@end


#import "MyPoint.h"

@implementation MyPoint
@synthesize x,y;

-(id)initWithX:(int)_x andY:(int)_y{
    if(_x==0)
        x=1;
    if(_y==0)
        y=1;
    x=_x;
    y=_y;
    return self;
}

-(id)copyWithZone:(NSZone *)zone{
    MyPoint* newPoint=[[MyPoint allocWithZone:zone] initWithX:x andY:y];
    return newPoint;
}

-(void)printOn{
    NSLog(@" x = %d , y = %d ",x,y);
}

@end

@implementation MyPoint(MoveSet)

-(void)moveToX:(int)_x andY:(int)_y{
    x=_x;
    y=_y;
}

@end