延展性，实现方法的私有化

//Study.m文件声明

1 #import <Foundation/Foundation.h>
2
3 @interface Study : NSObject
4
5 -(void)study;
6
7 @end

//Study.h文件实现

 1 #import "Study.h"
 2
 3 @interface Study ()//偷偷声明
 4
 5 -(void)playLOL;
 6
 7 -(void)playCF;
 8
 9 @end
10
11 @implementation Study
12
13 -(void)study
14
15 {
16     NSLog(@"我正在学习");
17
18     [self playCF];
19
20     [self playLOL];
21
22 }
23
24 -(void)playLOL//延展1
25
26 {
27     NSLog(@"我同样在玩LOL");
28 }
29
30 -(void)playCF//延展2
31
32 {
33     NSLog(@"我还在玩CF");
34 }
35
36 @end

//main.m文件中

Study *xiaoming=[[Study alloc]init];

[xiaoming study];

//

2015-11-10 18:53:47.972 test[7322:112328] 我正在学习
2015-11-10 18:53:47.972 test[7322:112328] 我在玩CF
2015-11-10 18:53:47.972 test[7322:112328] 我在玩LOL