各位大侠门请教OC对象方法前加“+”号和”-“号的区别？

1. //
   
2. // main.m
   
3. // TimeAfterTime
   
4. //
   
5. // Created by current on 9/18/15.
   
6. // Copyright :copyright: 2015 current. All rights reserved.
   
7. //
   
8. 
   
9. #import <Foundation/Foundation.h>
   
10. 
    
11. @interface Foo: NSObject
    
12. {
    
13. NSInteger uid;
    
14. }
    
15. -(void) init: (NSInteger) _id;
    
16. -(void) Bar;
    
17. +(void) Bar;
    
18. @end
    
19. 
    
20. @implementation Foo
    
21. 
    
22. -(void) init: (NSInteger)_id
    
23. {
    
24. uid = _id;
    
25. }
    
26. 
    
27. -(void) Bar
    
28. {
    
29. NSLog(@"My id is %ld", uid);
    
30. }
    
31. 
    
32. +(void) Bar
    
33. {
    
34. NSLog(@"Bar from Foo, No uid.");
    
35. }
    
36. @end
    
37. 
    
38. int main(int argc, const char * argv[]) {
    
39. @autoreleasepool {
    
40. Foo *p = [[Foo alloc] init];
    
41. [p Bar];
    
42. [Foo Bar];
    
43. }
    
44. return 0;
    
45. }

复制代码

+代表类方法，相当于C++里static
-是实例方法，在一个类被实例化后才可以被调用