多线程之NSOperation小结

Posted 2020-10-19 Dast1

一、NSOperation 抽象类

• NSOperation 是一个"抽象类"，不能直接使用。抽象类的用处是定义子类共有的属性和方法。

• NSOperation 是基于 GCD 做的面向对象的封装。
• 相比较 GCD 使用更加简单，并且提供了一些用 GCD 不是很好实现的功能。
• 苹果公司推荐使用的并发技术。

• 两个子类：
• NSInvocationOperation (调用)
• NSBlockOperation (块)

相比NSInvocationOperation推荐使用NSBlockOperation，代码简单，同时由于闭包性使它没有传参问题。

• NSOperationQueue 队列

 

已经学习过的抽象类

• UIGestureRecognizer
• CAAnimation
• CAPropertyAnimation

 

二、 NSOperation 和 GCD 的核心概念

• GCD的核心概念：将 任务(block) 添加到队列，并且指定执行任务的函数。
• NSOperation 的核心概念：将 操作 添加到 队列。

三、NSOperation 和 GCD的区别：

GCD

• 将任务（block）添加到队列(串行/并发/主队列)，并且指定任务执行的函数(同步/异步)
• GCD是底层的C语言构成的API
• ios 4.0 推出的，针对多核处理器的并发技术
• 在队列中执行的是由 block 构成的任务，这是一个轻量级的数据结构
• 要停止已经加入 queue 的 block 需要写复杂的代码
• 需要通过 Barrier 或者同步任务设置任务之间的依赖关系
• 只能设置队列的优先级
• 高级功能：
• 一次性 once
• 延迟操作 after
• 调度组

NSOperation

• 核心概念：把操作(异步)添加到队列(全局的并发队列)。
• OC 框架，更加面向对象，是对 GCD 的封装。
• iOS 2.0 推出的，苹果推出 GCD 之后，对 NSOperation 的底层全部重写。
• Operation作为一个对象，为我们提供了更多的选择。
• 可以跨队列设置操作的依赖关系
• 可以设置队列中每一个操作的优先级
• 高级功能：
• 最大操作并发数(GCD不好做)
• 继续/暂停/全部取消
• 跨队列设置操作的依赖关系

四、代码实践

  1 //
  2 //  ViewController.m
  3 //  NSOperationTest
  4 //
  5 //  Created by mayl on 2018/1/5.
  6 //  Copyright ? 2018年 huatu. All rights reserved.
  7 //
  8 
  9 #import "ViewController.h"
 10 
 11 @interface ViewController ()
 12 @property(nonatomic, strong) NSOperationQueue *gOpQueue;
 13 @end
 14 
 15 @implementation ViewController
 16 
 17 - (void)viewDidLoad {
 18     [super viewDidLoad];
 19     [self setUpUI];
 20     
 21 //    [self aysncCon];
 22     [self maxConCount];
 23 //    [self oftenUse];
 24 //    [self setUpDependence];
 25 //    [self waitUntilFinished];
 26 }
 27 
 28 - (void)setUpUI{
 29     
 30     //暂停，继续按钮
 31     UIButton *lBtn4Pause = [UIButton buttonWithType:UIButtonTypeCustom];
 32     [self.view addSubview:lBtn4Pause];
 33     
 34     lBtn4Pause.frame = CGRectMake(10, 100, 100, 50);
 35     [lBtn4Pause setTitle:@"挂起" forState:UIControlStateNormal];
 36     lBtn4Pause.titleLabel.numberOfLines = 0;
 37     [lBtn4Pause setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
 38     [lBtn4Pause addTarget:self action:@selector(pauseBtnDidClick:) forControlEvents:UIControlEventTouchUpInside];
 39     
 40     //取消所有任务按钮
 41     UIButton *lBtn4CancelAll = [UIButton buttonWithType:UIButtonTypeCustom];
 42     [self.view addSubview:lBtn4CancelAll];
 43     
 44     lBtn4CancelAll.frame = CGRectMake(150, 100, 100, 50);
 45     [lBtn4CancelAll setTitle:@"cancel all" forState:UIControlStateNormal];
 46     [lBtn4CancelAll setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
 47     [lBtn4CancelAll addTarget:self action:@selector(cancelAllBtnDidClick:) forControlEvents:UIControlEventTouchUpInside];
 48 }
 49 
 50 #pragma mark -  action
 51 
 52 /**
 53  队列挂起，当前"没有完成的操作"，是包含在队列的操作数中的。
 54  队列挂起，不会影响已经执行操作的执行状态。
 55  队列一旦被挂起，再添加的操作不会被调度。
 56  */
 57 - (void)pauseBtnDidClick:(UIButton *)btn{
 58     NSLog(@"队列中操作数：%zd", self.gOpQueue.operationCount);
 59     if (0 == self.gOpQueue.operationCount) {
 60         NSLog(@"队列中无操作");
 61         return;
 62     }
 63     
 64     NSLog(@"3:%d", self.gOpQueue.isSuspended);
 65     self.gOpQueue.suspended = !self.gOpQueue.isSuspended;
 66     NSLog(@"4:%d", self.gOpQueue.isSuspended);
 67     if (self.gOpQueue.isSuspended) {
 68         NSLog(@"队列挂起");
 69         [btn setTitle:@"继续"
 70              forState:UIControlStateNormal];
 71     }else{
 72         NSLog(@"队列继续");
 73         [btn setTitle:@"挂起"
 74              forState:UIControlStateNormal];
 75     }
 76 }
 77 
 78 /**
 79  取消队列中所有的操作。
 80  不会取消正在执行中的操作。
 81  不会影响队列的挂起状态
 82  */
 83 - (void)cancelAllBtnDidClick:(UIButton *)btn{
 84     if (0 == self.gOpQueue.operationCount) {
 85         NSLog(@"队列中无操作");
 86         return;
 87     }
 88     
 89     NSLog(@"取消队列中所有操作,此方法不会改变队列挂起状态");
 90     [self.gOpQueue cancelAllOperations];
 91     
 92     NSLog(@"1:%d", self.gOpQueue.isSuspended);
 93     self.gOpQueue.suspended = !self.gOpQueue.isSuspended;
 94     NSLog(@"2:%d", self.gOpQueue.isSuspended);
 95 }
 96 
 97 /** 默认是：异步，并发 */
 98 - (void)aysncCon{
 99     NSOperationQueue *lQueue = [[NSOperationQueue alloc] init];
100     for (int i = 0; i < 20; ++i) {
101         [lQueue addOperationWithBlock:^{
102             [NSThread sleepForTimeInterval:1];
103             NSLog(@"%d,%@", i, [NSThread currentThread]);
104         }];
105     }
106 }
107 
108 /** 最大并发数:The maximum number of queued operations that can execute at the same time.*/
109 - (void)maxConCount{
110     NSOperationQueue *lQueue = [[NSOperationQueue alloc] init];
111     lQueue.maxConcurrentOperationCount = 2;
112     for (int i = 0; i < 30; ++i) {
113         [lQueue addOperationWithBlock:^{
114             [NSThread sleepForTimeInterval:1];
115             NSLog(@"%d,%@", i, [NSThread currentThread]);
116         }];
117     }
118     
119     self.gOpQueue = lQueue;
120 }
121 
122 /** 常用：子线程耗时，主线程更新UI */
123 - (void)oftenUse{
124     NSOperationQueue *lQ = [[NSOperationQueue alloc] init];
125     
126     [lQ addOperationWithBlock:^{
127         NSLog(@"耗时操作开始,%@", [NSThread currentThread]);
128         [NSThread sleepForTimeInterval:3];
129         NSLog(@"耗时操作结束");
130         
131         [[NSOperationQueue mainQueue] addOperationWithBlock:^{
132             NSLog(@"主线程更新UI，%@",
133                   [NSThread currentThread]);
134         }];
135         
136     }];
137 }
138 
139 /** 设置依赖 */
140 - (void)setUpDependence{
141     NSOperationQueue *lQ = [[NSOperationQueue alloc] init];
142     
143     [lQ addOperationWithBlock:^{
144         [NSThread sleepForTimeInterval:1];
145         NSLog(@"do something,%@",
146               [NSThread currentThread]);
147     }];
148     
149     NSBlockOperation *lOp1 = [NSBlockOperation blockOperationWithBlock:^{
150         [NSThread sleepForTimeInterval:1];
151         NSLog(@"1：登录,%@",
152               [NSThread currentThread]);
153     }];
154     
155     NSBlockOperation *lOp2 = [NSBlockOperation blockOperationWithBlock:^{
156         [NSThread sleepForTimeInterval:1];
157         NSLog(@"2：购买点券,%@",
158               [NSThread currentThread]);
159     }];
160     
161     NSBlockOperation *lOp3 = [NSBlockOperation blockOperationWithBlock:^{
162         [NSThread sleepForTimeInterval:1];
163         NSLog(@"3：使用点券,%@",
164               [NSThread currentThread]);
165     }];
166     
167     NSBlockOperation *lOp4 = [NSBlockOperation blockOperationWithBlock:^{
168         [NSThread sleepForTimeInterval:1];
169         NSLog(@"4：返回结果,%@",
170               [NSThread currentThread]);
171     }];
172     
173     [lOp2 addDependency:lOp1];
174     [lOp3 addDependency:lOp2];
175     [lOp4 addDependency:lOp3];
176     
177     //下面加的话会循环依赖，导致任何操作都无法进行，程序不会崩溃。
178 //    [lOp1 addDependency:lOp4];
179     
180     [lQ addOperations:@[lOp4, lOp3] waitUntilFinished:NO];
181     [lQ addOperations:@[lOp2, lOp1] waitUntilFinished:NO];
182 }
183 
184 /**执行效果如下：
185  2018-01-05 19:54:31.721539+0800 NSOperationTest[578:156322] come in
186  2018-01-05 19:54:33.727691+0800 NSOperationTest[578:156342] 0：do others,<NSThread: 0x1c027f740>{number = 3, name = (null)}
187  2018-01-05 19:54:34.731836+0800 NSOperationTest[578:156342] 1：登录,<NSThread: 0x1c027f740>{number = 3, name = (null)}
188  2018-01-05 19:54:35.737375+0800 NSOperationTest[578:156342] 2：购买点券,<NSThread: 0x1c027f740>{number = 3, name = (null)}
189  2018-01-05 19:54:36.742936+0800 NSOperationTest[578:156342] 3：使用点券,<NSThread: 0x1c027f740>{number = 3, name = (null)}
190  2018-01-05 19:54:37.746491+0800 NSOperationTest[578:156342] 4：show Time,<NSThread: 0x1c027f740>{number = 3, name = (null)}
191  2018-01-05 19:54:38.764408+0800 NSOperationTest[578:156341] 5：[lQ addOperations:@[lOp4, lOp3] waitUntilFinished:YES];实现了不设置依赖，且我需要最后执行,<NSThread: 0x1c04631c0>{number = 4, name = (null)}
192  */
193 - (void)waitUntilFinished{
194     NSOperationQueue *lQ = [[NSOperationQueue alloc] init];
195     
196     NSLog(@"come in");
197     NSBlockOperation *lOp0 = [NSBlockOperation blockOperationWithBlock:^{
198         [NSThread sleepForTimeInterval:2];
199         NSLog(@"0：do others,%@",
200               [NSThread currentThread]);
201     }];
202     
203     NSBlockOperation *lOp1 = [NSBlockOperation blockOperationWithBlock:^{
204         [NSThread sleepForTimeInterval:1];
205         NSLog(@"1：登录,%@",
206               [NSThread currentThread]);
207     }];
208     
209     NSBlockOperation *lOp2 = [NSBlockOperation blockOperationWithBlock:^{
210         [NSThread sleepForTimeInterval:1];
211         NSLog(@"2：购买点券,%@",
212               [NSThread currentThread]);
213     }];
214     
215     NSBlockOperation *lOp3 = [NSBlockOperation blockOperationWithBlock:^{
216         [NSThread sleepForTimeInterval:1];
217         NSLog(@"3：使用点券,%@",
218               [NSThread currentThread]);
219     }];
220     
221     NSBlockOperation *lOp4 = [NSBlockOperation blockOperationWithBlock:^{
222         [NSThread sleepForTimeInterval:1];
223         NSLog(@"4：show Time,%@",
224               [NSThread currentThread]);
225     }];
226     
227     NSBlockOperation *lOp5 = [NSBlockOperation blockOperationWithBlock:^{
228         [NSThread sleepForTimeInterval:1];
229         
230         NSLog(@"5：[lQ addOperations:@[lOp4, lOp3] waitUntilFinished:YES];实现了不设置依赖，且我需要最后执行,%@",
231               [NSThread currentThread]);
232     }];
233 
234     [lOp2 addDependency:lOp1];
235     [lOp3 addDependency:lOp2];
236     [lOp4 addDependency:lOp3];
237 
238     //执行顺序跟在数组中的顺序无关
239     //waitUntilFinished:If YES, the current thread is blocked until all of the specified operations finish executing. If NO, the operations are added to the queue and control returns immediately to the caller.(If YES，当前线程会被阻塞，直到数组中所有操作执行完毕。下局代码是直到lOp5执行完毕，才会执行后续操作)
240     [lQ addOperations:@[lOp0] waitUntilFinished:YES];
241     
242     [lQ addOperations:@[lOp2, lOp1] waitUntilFinished:NO];
243     [lQ addOperations:@[lOp4, lOp3] waitUntilFinished:YES];
244     
245     [lQ addOperation:lOp5];
246 }
247 
248 @end