iOS UI-线程（NSThread）及其安全隐患

一、基本使用

  1 //
  2 //  ViewController.m
  3 //  IOS_0116_NSThread
  4 //
  5 //  Created by ma c on 16/1/16.
  6 //  Copyright (c) 2016年 博文科技. All rights reserved.
  7 //
  8
  9 #import "ViewController.h"
 10 #import <pthread.h>
 11
 12 /*
 13  线程的实现方案
 14  pthread
 15  NSThread
 16  GCD
 17  NSOperation
 18  */
 19 @interface ViewController ()
 20
 21 @end
 22
 23 @implementation ViewController
 24
 25
 26 - (void)viewDidLoad {
 27     [super viewDidLoad];
 28
 29     //[self pthread];
 30
 31 }
 32 #pragma mark - 创建线程NSThread
 33 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
 34 {
 35 //    [self createThread1];
 36 //    [self createThread2];
 37     [self createThread3];
 38
 39 }
 40 #pragma mark - 创建线程3
 41 - (void)createThread3
 42 {
 43     //隐式创建线程
 44     [self performSelector:@selector(download:) withObject:@"http:www.bowen.cn"];
 45     [self download:@"http:www.bowen.cn"];
 46
 47     [self performSelectorInBackground:@selector(download:) withObject:@"http:www.bowen.cn"];
 48
 49     [self performSelector:@selector(download:) onThread:[NSThread mainThread] withObject:@"http:www.bowen.cn" waitUntilDone:nil];
 50
 51 }
 52
 53
 54 #pragma mark - 创建线程2
 55 - (void)createThread2
 56 {
 57     //创建后并启动线程
 58     [NSThread detachNewThreadSelector:@selector(download:) toTarget:self withObject:@"http:www.bowen.cn"];
 59 }
 60 - (void)download:(NSString *)url
 61 {
 62     NSLog(@"\ndownload----%@",[NSThread mainThread]);
 63
 64
 65     NSLog(@"\ndownload----%@----%@",url,[NSThread currentThread]);
 66 }
 67
 68 #pragma mark - 创建线程1
 69 //启动线程 - 进入就绪状态 -（CPU调度当前线程）- 运行状态 - 线程任务完毕，自动进入死亡状态
 70 //                                               -调用sleep方法或者等待同步锁 - 阻塞状态
 71 - (void)createThread1
 72 {
 73     //创建线程
 74     NSThread *thread = [[NSThread alloc] initWithTarget:self selector:@selector(download) object:nil];
 75     //设置线程的名字
 76     thread.name = @"下载线程";
 77     //当前线程是否是主线程
 78     [thread isMainThread];
 79     //启动线程
 80     [thread start];
 81
 82     //判断当前方法是否是在主线程主线程中执行
 83     [NSThread isMainThread];
 84 }
 85
 86 - (void)download
 87 {
 88     NSLog(@"\ndownload----%@",[NSThread mainThread]);
 89
 90     //阻塞线程
 91     [NSThread sleepForTimeInterval:3];
 92     [NSThread  sleepUntilDate:[NSDate dateWithTimeIntervalSinceNow:3]];
 93
 94     NSLog(@"\ndownload----%@",[NSThread currentThread]);
 95
 96     //强制停止线程
 97     [NSThread exit];
 98     NSLog(@"\ndownload----%@",@"exit");
 99 }
100
101
102 #pragma mark - pthread
103 - (void)pthread
104 {
105     NSLog(@"\nviewDidLoad-------%@",[NSThread currentThread]);
106
107     //创建线程
108     pthread_t myRestrict;
109     pthread_create(&myRestrict, NULL, run, NULL);
110 }
111
112 void *run(void *data)
113 {
114     NSLog(@"\nrun-------%@",[NSThread currentThread]);
115
116     return NULL;
117 }
118
119 @end

二、线程安全

 1 //
 2 //  ViewController.m
 3 //  IOS_0117_线程的安全隐患
 4 //
 5 //  Created by ma c on 16/1/17.
 6 //  Copyright (c) 2016年 博文科技. All rights reserved.
 7 //
 8
 9 #import "ViewController.h"
10
11 @interface ViewController ()
12
13 @property (nonatomic, strong) NSThread *thread1;
14 @property (nonatomic, strong) NSThread *thread2;
15
16 //剩余票数
17 @property (nonatomic, assign) int leftTicketCount;
18
19 @end
20
21 @implementation ViewController
22 /*
23  资源共享
24  一块资源可能会被多个线程共享，也就是多个线程可能会访问[同一块资源]
25
26  比如多个线程访问同一个对象、同一个变量、同一个文件
27
28  当多个线程访问同一块资源时，很容易引发[数据错乱和数据安全]问题
29
30  */
31
32 - (void)viewDidLoad {
33     [super viewDidLoad];
34
35     self.leftTicketCount = 50;
36
37     self.thread1 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
38     self.thread1.name = @"1号窗口";
39     self.thread2 = [[NSThread alloc] initWithTarget:self selector:@selector(saleTicket) object:nil];
40     self.thread2.name = @"2号窗口";
41
42
43 }
44
45 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
46 {
47     [self.thread1 start];
48     [self.thread2 start];
49 }
50 /*
51  互斥锁使用格式
52  @synchronized(锁对象) { // 需要锁定的代码  }
53  注意：锁定1份代码只用1把锁，用多把锁是无效的
54
55  互斥锁的优缺点
56  优点：能有效防止因多线程抢夺资源造成的数据安全问题
57  缺点：需要消耗大量的CPU资源
58
59  互斥锁的使用前提：多条线程抢夺同一块资源
60
61  相关专业术语：线程同步
62  线程同步的意思是：多条线程在同一条线上执行（按顺序地执行任务）
63  互斥锁，就是使用了线程同步技术
64
65  */
66 - (void)saleTicket
67 {
68     while (1) {
69
70         @synchronized(self){ //开始枷锁 小括号里面放的是锁对象
71             int count = self.leftTicketCount;
72             if (count>0) {
73                 self.leftTicketCount = count -1;
74                 NSLog(@"%@卖了一张票，剩余%d张票",[NSThread currentThread].name, self.leftTicketCount);
75             }else{
76                 return; //退出循环 break
77             }
78
79         }//解锁
80
81     }
82 }
83
84 - (void)didReceiveMemoryWarning {
85     [super didReceiveMemoryWarning];
86     // Dispose of any resources that can be recreated.
87 }
88
89 @end

三、线程间通信