为什么编译器总是报这个错呢？ 求解答 ，谢谢

10.m:83:13: error: unknown receiver 'Point1'; did you mean

      'Point2D'?

    return [Point1 distanceWithOther:point2];

            ^~~~~~

            Point2D

10.m:10:12: note: 'Point2D' declared here

@interface Point2D : NSObject

           ^

10.m:83:20: warning: class method '+distanceWithOther:' not

      found (return type defaults to 'id')

      [-Wobjc-method-access]

    return [Point1 distanceWithOther:point2];

                   ^~~~~~~~~~~~~~~~~

10.m:83:12: error: returning 'id' from a function with

      incompatible result type 'double'

    return [Point1 distanceWithOther:point2];

           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1 warning and 2 errors generated.

1. #import <Foundation/Foundation.h>
   
2. #import <math.h>
   
3. 
   
4. @interface Point2D : NSObject
   
5. {
   
6.     double _x;
   
7.     double _y;
   
8. }
   
9. 
   
10. // x的setter和getter
    
11. - (void)setX:(double)x;
    
12. - (double)x;
    
13. 
    
14. // y的setter和getter
    
15. - (void)setY:(double)y;
    
16. - (double)y;
    
17. 
    
18. //同时设置x和y
    
19. - (void)setX:(double)x andY:(double)y;
    
20. 
    
21. //计算和其他点的距离
    
22. - (double)distanceWithOther:(Point2D *)other;
    
23. 
    
24. //类方法计算两个点之间的距离
    
25. + (double)distanceBetweenPoint1:(Point2D *)point1 andPoint2:(Point2D *)point2;
    
26. 
    
27. @end
    
28. 
    
29. @implementation Point2D
    
30. 
    
31. // x的setter和getter
    
32. - (void)setX:(double)x
    
33. {
    
34.     _x = x;
    
35. }
    
36. - (double)x
    
37. {
    
38.     return _x;
    
39. }
    
40. 
    
41. // y的setter和getter
    
42. - (void)setY:(double)y
    
43. {
    
44.     _y = y;
    
45. }
    
46. - (double)y
    
47. {
    
48.     return _y;
    
49. }
    
50. 
    
51. //同时设置x和y
    
52. - (void)setX:(double)x andY:(double)y
    
53. {
    
54.     _x = x;
    
55.     _y = y;
    
56. }
    
57. 
    
58. //计算和其他点的距离
    
59. - (double)distanceWithOther:(Point2D *)other
    
60. {
    
61.     //计算X的差值
    
62.     double xMinus = [self x] - [other x];
    
63.     //计算Y的差值
    
64.     double yMinus = [self y] - [other y];
    
65.     //计算X差值的平方
    
66.     double xSquare = pow(xMinus,2);
    
67.     //计算Y差值的平方
    
68.     double ySquare = pow(yMinus,2);
    
69.     //计算xMinus和yMinus的和的开跟
    
70.     return sqrt(xSquare + ySquare);
    
71. }
    
72. 
    
73. //类方法计算两个点之间的距离
    
74. + (double)distanceBetweenPoint1:(Point2D *)point1 andPoint2:(Point2D *)point2
    
75. {
    
76.     //代码重构
    
77.     return [Point1 distanceWithOther:point2];
    
78. }
    
79. 
    
80. @end
    
81. 
    
82. int main ()
    
83. {
    
84.     Point2D *point1 = [Point2D new];
    
85.     Point2D *point2 = [Point2D new];
    
86.     [point1 setX:20 andY:40];
    
87.     [point2 setX:18 andY:28];
    
88.     double c = [point1 distanceWithOther:point2];
    
89.     double c1 = [Point2D distanceBetweenPoint1:point1 andPoint2:point2];
    
90.     NSLog(@"%f----%f",c,c1);
    
91.     return 0;
    
92. }

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