前言
针对于多线程同步以及依赖做一个小小的总结，以及当实际情况中比如在使用AFNetworking进行多次网络请求中如何进行线程依赖。
模拟数据
线程同步，最终执行完成操作（比如刷新UI）。
线程同步使用的是dispatch_group相关来实现。
测试代码：
//第一步创建队列
dispatch_queue_t customQuue = dispatch_queue_create("com.manman.network", DISPATCH_QUEUE_CONCURRENT);
//第二步创建组
dispatch_group_t customGroup = dispatch_group_create();
//第三步添加任务
dispatch_group_async(customGroup, customQuue, ^{
NSLog(@"吃饭");
});
dispatch_group_async(customGroup, customQuue, ^{
NSLog(@"洗澡");
});
dispatch_group_async(customGroup, customQuue, ^{
NSLog(@"睡觉");
});
dispatch_group_async(customGroup, customQuue, ^{
NSLog(@"起床");
});
//第四步通知
dispatch_group_notify(customGroup, dispatch_get_main_queue(), ^{
NSLog(@"任务完成");
});
打印结果：
可以看到没什么问题，实现了线程同步，但是没有实现线程依赖。
如何实现线程依赖，依赖NSOperationQueue.
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"吃饭");
}];
NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"洗澡");
}];
NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"起床");
}];
NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"睡觉");
}];
NSBlockOperation *operation5 = [NSBlockOperation blockOperationWithBlock:^{
NSLog(@"第二天");
}];
//4.设置依赖
[operation2 addDependency:operation1]; //任务二依赖任务一
[operation3 addDependency:operation2]; //任务三依赖任务二
[operation4 addDependency:operation3]; //任务四依赖任务三
[operation5 addDependency:operation4];
//5.创建队列并加入任务
NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [queue addOperations:@[operation3, operation2, operation1,operation4,operation5] waitUntilFinished:NO];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
NSLog(@"任务完成");
}];
可以看到是同步，并且依赖。
模拟数据实现了同步以及依赖，那么如果换做是真实的网络请求怎么样。
使用AFNetworking多次请求，实现线程同步以及依赖。
首先定义一个请求方法，（这里采用的是真实数据）
/**发起请求*/
-(void)requestWithType:(NSString *)type{
AFHTTPSessionManager *manger =[AFHTTPSessionManager manager];
manger.responseSerializer = [AFHTTPResponseSerializer serializer];
manger.requestSerializer = [AFHTTPRequestSerializer serializer];
manger.requestSerializer.timeoutInterval = 30;
manger.responseSerializer.acceptableContentTypes=[NSSet setWithObjects:@"application/json",@"text/json",@"text/javascript",@"text/html",nil,nil];
NSString *url = @"http://122.112.244.62/elevator/api/index.php/elevator/info?id=12345678711234567878";
[manger GET:url parameters:nil progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"%@",type);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
}];
}
同模拟数据，首先实现数据同步，只需要换个方法就行了吧。。
//第一步创建队列
dispatch_queue_t customQuue = dispatch_queue_create("com.manman.network", DISPATCH_QUEUE_CONCURRENT);
//第二步创建组
dispatch_group_t customGroup = dispatch_group_create();
//第三步添加任务
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"吃饭"];
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"洗澡"];
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"睡觉"];
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"起床"];
});
//第四步通知
dispatch_group_notify(customGroup, dispatch_get_main_queue(), ^{
NSLog(@"任务完成");
});
8F4B6CFF-D8CD-4D7F-9D3F-A3FA5742BA14.png
是不是好奇怪，一样的方法只是换成AFNetworking，结果就不一样了，并没有实现线程同步，我们也都知道AFNetworking在进行网络请求的时候又开启了线程。
那么如何实现线程同步呢，借助信号量。
第一种方式：使用dispatch_semaphore_signal。
dispatch_semaphore_create 创建一个semaphore
dispatch_semaphore_signal 发送一个信号
dispatch_semaphore_wait 等待信号
三个函数介绍：
第一个函数：创建一个整形数值的信号，即：信号的总量
第二个函数：发送一个信号,让信号总量增加1
第三个函数：首先判断信号量是否大于零，如果大于零则减掉1个信号量，往下执行，如果等于零则阻塞该线程
如何使用信号量来实现线程同步呢，
首先对请求方法做个改动
/**发起请求*/
-(void)requestWithType:(NSString *)type{
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
AFHTTPSessionManager *manger =[AFHTTPSessionManager manager];
manger.responseSerializer = [AFHTTPResponseSerializer serializer];
manger.requestSerializer = [AFHTTPRequestSerializer serializer];
manger.requestSerializer.timeoutInterval = 30;
manger.responseSerializer.acceptableContentTypes=[NSSet setWithObjects:@"application/json",@"text/json",@"text/javascript",@"text/html",nil,nil];
NSString *url = @"http://122.112.244.62/elevator/api/index.php/elevator/info?id=12345678711234567878";
[manger GET:url parameters:nil progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
//信号量+1
long x = dispatch_semaphore_signal(sema);
NSLog(@"%@ --%ld",type,x);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
//信号量+1
dispatch_semaphore_signal(sema);
}];
//信号量-1
long x = dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
NSLog(@"%@了 --%ld",type,x);
}
看一下结果：
2.png
可以看到实现了线程同步，任务完成在最后。
第二种
dispatch_group_enter：通知group，下面的任务马上要放到group中执行了。
dispatch_group_leave：通知group，任务完成了，该任务要从group中移除了。
//第一步创建队列
dispatch_queue_t customQuue = dispatch_queue_create("com.manman.network", DISPATCH_QUEUE_CONCURRENT);
//第二步创建组
dispatch_group_t customGroup = dispatch_group_create();
//第三步添加任务
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"吃饭" group:customGroup];
;
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"洗澡" group:customGroup];
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"睡觉" group:customGroup];
});
dispatch_group_async(customGroup, customQuue, ^{
[self requestWithType:@"起床" group:customGroup];
});
//第四步通知
dispatch_group_notify(customGroup, dispatch_get_main_queue(), ^{
NSLog(@"任务完成");
});
请求方式修改：
/**发起请求*/
-(void)requestWithType:(NSString *)type group:(dispatch_group_t)group{
dispatch_group_enter(group);
AFHTTPSessionManager *manger =[AFHTTPSessionManager manager];
manger.responseSerializer = [AFHTTPResponseSerializer serializer];
manger.requestSerializer = [AFHTTPRequestSerializer serializer];
manger.requestSerializer.timeoutInterval = 30;
manger.responseSerializer.acceptableContentTypes=[NSSet setWithObjects:@"application/json",@"text/json",@"text/javascript",@"text/html",nil,nil];
NSString *url = @"http://122.112.244.62/elevator/api/index.php/elevator/info?id=12345678711234567878";
[manger GET:url parameters:nil progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"%@",type);
dispatch_group_leave(group);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
dispatch_group_leave(group);
}];
}
3.png
可以看到实现了线程同步。但是并未依赖。
如何实现线程依赖。
NSOperation 结合信号量来实现。
NSBlockOperation *operation1 = [NSBlockOperation blockOperationWithBlock:^{
[self requestWithType:@"吃饭"];
}];
NSBlockOperation *operation2 = [NSBlockOperation blockOperationWithBlock:^{
[self requestWithType:@"洗澡"];
}];
NSBlockOperation *operation3 = [NSBlockOperation blockOperationWithBlock:^{
[self requestWithType:@"起床"];
}];
NSBlockOperation *operation4 = [NSBlockOperation blockOperationWithBlock:^{
[self requestWithType:@"睡觉"];
}];
NSBlockOperation *operation5 = [NSBlockOperation blockOperationWithBlock:^{
[self requestWithType:@"第二天"];
}];
NSBlockOperation *operation6 = [NSBlockOperation blockOperationWithBlock:^{
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
NSLog(@"任务完成,刷新UI");
}];
}];
//4.设置依赖
[operation2 addDependency:operation1]; //任务二依赖任务一
[operation3 addDependency:operation2]; //任务三依赖任务二
[operation4 addDependency:operation3]; //任务四依赖任务三
[operation5 addDependency:operation4];
[operation6 addDependency:operation5];
//5.创建队列并加入任务
NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [queue addOperations:@[operation3, operation2, operation1,operation4,operation5,operation6] waitUntilFinished:NO];
}
/**发起请求*/
-(void)requestWithType:(NSString *)type{
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
AFHTTPSessionManager *manger =[AFHTTPSessionManager manager];
manger.responseSerializer = [AFHTTPResponseSerializer serializer];
manger.requestSerializer = [AFHTTPRequestSerializer serializer];
manger.requestSerializer.timeoutInterval = 30;
manger.responseSerializer.acceptableContentTypes=[NSSet setWithObjects:@"application/json",@"text/json",@"text/javascript",@"text/html",nil,nil];
NSString *url = @"http://122.112.244.62/elevator/api/index.php/elevator/info?id=12345678711234567878";
[manger GET:url parameters:nil progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"%@",type);
dispatch_semaphore_signal(sema);
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
dispatch_semaphore_signal(sema);
}];
dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
}
打印结果：
3A128FD1-944F-4CD2-BA3A-D9EA5BA72295.png