iOS GCD线程同步以及AFNetworking多次请求线程依赖

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:

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//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:
QQ20180510-170344@2x.png

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.

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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");
}];

QQ20180510-175130@2x.png

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)

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/**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。。

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//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");
});

看一下结果,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

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/**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。

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//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:

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/**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);
}];
}

打印结果: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。

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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