一次性代码-06-GCD 

 1 //
 2 //  ViewController.m
 3 //  06一次性代码-GCD
 4 //
 5 //  Created by mac on 16/4/21.
 6 //  Copyright © 2016年 mac. All rights reserved.
 7 //
 8 
 9 #import "ViewController.h"
10 
11 @interface ViewController ()
12 
13 @property (assign, nonatomic) BOOL isHave;
14 
15 
16 @end
17 
18 @implementation ViewController
19 
20 - (void)viewDidLoad {
21     [super viewDidLoad];
22 
23 }
24 
25 /**
26  *  1. flag保证只打印一次
27  */
28 - (void)download {
29     
30     if (self.isHave) return;
31     
32     NSLog(@"ishave");
33     self.isHave = YES;
34 
35 }
36 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
37     
38     [self downLoadDispatch];
39 }
40 
41 /**
42  *  2. dispatch_once_t保证只打印一次
43  */
44 - (void)downLoadDispatch {
45     
46     static dispatch_once_t onceToken;
47     dispatch_once(&onceToken, ^{
48        
49     NSLog(@"downLoadDispatch");
50     });
51 }
52 
53 @end

 

posted on 2016-04-21 15:15  爱你久久iOS  阅读(329)  评论(0)  编辑  收藏  举报

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