#import 
     
      #import 
      
       @interface Point2D : NSObject{    double _x; // x值    double _y; // y值}// x值的getter和setter- (void)setX:(double)x;- (double)x;// y值的getter和setter- (void)setY:(double)y;- (double)y;// 同时设置x和y- (void)setX:(double)x andY:(double)y;//计算根其他点距离- (double)distanceWithOther:(Point2D *)other;//类方法计算两个点之间的距离+ (double)distanceWithOther1:(Point2D *)p1 andPoint2:(Point2D *)p2;@end@implementation Point2D// x值的getter和setter- (void)setX:(double)x{    self->_x = x;}- (double)x{    return _x;}// y值的getter和setter- (void)setY:(double)y{    self->_y = y;}- (double)y{    return _y;}// 同时设置x和y- (void)setX:(double)x andY:(double)y{    [self setX:x];    [self setY:y];}//计算两个点之间的距离- (double)distanceWithOther:(Point2D *)other{    //return [Point2D distanceWithOther1:self andPoint2:other];    double xDelta = [self x] - [other x];        double xDeltaPF = pow(xDelta, 2);        double yDelta = [self y] - [other y];        double yDeltaPF = pow(yDelta, 2);        return sqrt(xDeltaPF + yDeltaPF);}//类方法计算两个点之间的距离+ (double)distanceWithOther1:(Point2D *)p1 andPoint2:(Point2D *)p2{    // 调用在类方法中的对方法    return [p1 distanceWithOther:p2];}@end@interface Circle : NSObject{    //半径    double _radius;    //圆心    Point2D *_point;}// 半径的getter和setter- (void)setRadius:(double)radius;- (double)radius;//圆心的getter和setter- (void)setPoint:(Point2D *)point;- (Point2D *)point;//判断两个圆是否重叠//类方法+ (BOOL)isInteractBetweenCircle1:(Circle *)c1 andCircle2:(Circle *)c2;//对象方法- (BOOL)isInteractBetweenCircle:(Circle *)other;@end@implementation Circle// 半径的getter和setter- (void)setRadius:(double)radius{    _radius = radius;}- (double)radius{    return _radius;}//圆心的getter和setter- (void)setPoint:(Point2D *)point{    _point = point;}- (Point2D *)point;{    return _point;}//对象方法- (BOOL)isInteractBetweenCircle:(Circle *)other{//看圆心距离和半径长度关系    //圆心长度    Point2D *p1 = [self point];    Point2D *p2 = [other point];    double distance = [p1 distanceWithOther:p2]; //5    //半径和    NSLog(@"圆心长 %f",distance);    double radiusSum = [self radius] + [other radius];  //7     NSLog(@"半径长 %f",radiusSum);    return distance < radiusSum;}//判断是否重叠+ (BOOL)isInteractBetweenCircle1:(Circle *)c1 andCircle2:(Circle *)c2{    return [c1 isInteractBetweenCircle:c2];}@endint main(){    //凡是对象都有*    /*    Point2D *p1 = [Point2D new];    [p1 setX:10 andY:15];        Point2D *p2 = [Point2D new];        [p2 setX:10 andY:12];        //double d1 = [p1 distanceWithOther:p2];    double d1 = [Point2D distanceWithOther1:p1 andPoint2:p2];    NSLog(@"%f ", d1);        */    //c1    Circle *c1 = [Circle new];    [c1 setRadius:5];    Point2D *p1 = [Point2D new];        [p1 setX:10 andY:15];        [c1 setPoint:p1];        [[c1 point] setX:15];    //c1 5  (15,15)    //c2    Circle *c2 = [Circle new];    [c2 setRadius:2];    Point2D *p2 = [Point2D new];        [p2 setX:12 andY:19];    //设置圆心    [c2 setPoint:p2];        //c2 2 (12,19)    BOOL b1 = [c1 isInteractBetweenCircle:c2];    NSLog(@"%d",b1);    if (b1) {        NSLog(@"重叠");    }else        NSLog(@"不重叠");    return 0;}