1.
dispatch_group_enter(group);
dispatch_group_leave(group);
dispatch_group_notify(group1, queue1,block);
在这种组合下，根据任务是同步、异步又分为两种，这两种组合的执行代码与运行结果如下：
第一种：同步任务时
dispatch_queue_t queue2 = dispatch_queue_create("dispatchGroupMethod2.queue2", DISPATCH_QUEUE_CONCURRENT);
dispatch_group_t group2 = dispatch_group_create();
dispatch_group_enter(group2);
dispatch_sync(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-同步任务执行-:%ld",@"任务1",(long)i);
}
dispatch_group_leave(group2);
});
dispatch_group_enter(group2);
dispatch_sync(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-同步任务执行-:%ld",@"任务2",(long)i);
}
dispatch_group_leave(group2);
});
// //等待上面的任务全部完成后，会往下继续执行 （会阻塞当前线程）
// dispatch_group_wait(group2, DISPATCH_TIME_FOREVER);
//等待上面的任务全部完成后，会收到通知执行block中的代码 （不会阻塞线程）
dispatch_group_notify(group2, queue2, ^{
NSLog(@"Method2-全部任务执行完成");
});
同步任务执行结果：
第二种：异步任务时
dispatch_queue_t queue2 = dispatch_queue_create("dispatchGroupMethod2.queue2", DISPATCH_QUEUE_CONCURRENT);
dispatch_group_t group2 = dispatch_group_create();
dispatch_group_enter(group2);
dispatch_async(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-异步任务执行-:%ld",@"任务1",(long)i);
}
dispatch_group_leave(group2);
});
dispatch_group_enter(group2);
dispatch_async(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-异步任务执行-:%ld",@"任务2",(long)i);
}
dispatch_group_leave(group2);
});
// //等待上面的任务全部完成后，会往下继续执行 （会阻塞当前线程）
// dispatch_group_wait(group2, DISPATCH_TIME_FOREVER);
//等待上面的任务全部完成后，会收到通知执行block中的代码 （不会阻塞线程）
dispatch_group_notify(group2, queue2, ^{
NSLog(@"Method2-全部任务执行完成");
});
异步任务执行结果：
https://www.cnblogs.com/zhou--fei/p/6747938.html
2.
创建一个信号量，作为全局变量。
并初始化，信号量为0
dispatch_semaphore_t semaphore;
semaphore = dispatch_semaphore_create(0);
创建一个dispatch_group_t，开启两个组异步线程（dispatch_group_async），分别执行两个网络请求。
一个组通知线程（dispatch_group_notify），用于接收前面两个线程的结果。
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_async(group, queue, ^{
[weakSelf loadRelationDetail];//请求1
});
dispatch_group_async(group, queue, ^{
[weakSelf loadRelationReward];//请求2
});
dispatch_group_notify(group, queue, ^{
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
//合并（此处是数据处理，你可根据具体业务需求进行处理）
NSMutableArray *arr = [NSMutableArray array];
[arr addObjectsFromArray:weakSelf.arr1];
[arr addObjectsFromArray:weakSelf.arr2];
//排序
if (arr.count > 1) {
weakSelf.sumArr = [arr sortedArrayUsingComparator:^NSComparisonResult(ZHShareItem *obj1, ZHShareItem *obj2) {
return [obj1.createTime compare:obj2.createTime];
}];
}else{
weakSelf.sumArr = arr;
}
//有数据刷新
if (weakSelf.sumArr.count > 0) {
//在主线程刷新页面
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf initTableView];
});
}
});https://www.jianshu.com/p/4e997f5deda9
3.afnetworking
为每一个NSURLSessionDownloadTask创建AFURLSessionManagerTaskDelegate，把请求的completionHandler也放在delegate。
从统一的回调didCompleteWithError到delegate的didCompleteWithError，再调用completionHandler返回。
- (void)addDelegateForDownloadTask:(NSURLSessionDownloadTask *)downloadTask
progress:(void (^)(NSProgress *downloadProgress)) downloadProgressBlock
destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler
{
AFURLSessionManagerTaskDelegate *delegate = [[AFURLSessionManagerTaskDelegate alloc] init];
delegate.manager = self;
delegate.completionHandler = completionHandler; if (destination) {
delegate.downloadTaskDidFinishDownloading = ^NSURL * (NSURLSession * __unused session, NSURLSessionDownloadTask *task, NSURL *location) {
return destination(location, task.response);
};
} downloadTask.taskDescription = self.taskDescriptionForSessionTasks; [self setDelegate:delegate forTask:downloadTask]; delegate.downloadProgressBlock = downloadProgressBlock;
}
response
- (void)URLSession:(NSURLSession *)session
task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
AFURLSessionManagerTaskDelegate *delegate = [self delegateForTask:task]; // delegate may be nil when completing a task in the background
if (delegate) {
[delegate URLSession:session task:task didCompleteWithError:error];
...
//需要加锁
- (AFURLSessionManagerTaskDelegate *)delegateForTask:(NSURLSessionTask *)task {
NSParameterAssert(task); AFURLSessionManagerTaskDelegate *delegate = nil;
[self.lock lock];
delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)];
[self.lock unlock]; return delegate;
} ...
//每一个delegate #pragma mark - NSURLSessionTaskDelegate - (void)URLSession:(__unused NSURLSession *)session
task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
__strong AFURLSessionManager *manager = self.manager; __block id responseObject = nil; __block NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer; //Performance Improvement from #2672
NSData *data = nil;
if (self.mutableData) {
data = [self.mutableData copy];
//We no longer need the reference, so nil it out to gain back some memory.
self.mutableData = nil;
} if (self.downloadFileURL) {
userInfo[AFNetworkingTaskDidCompleteAssetPathKey] = self.downloadFileURL;
} else if (data) {
userInfo[AFNetworkingTaskDidCompleteResponseDataKey] = data;
} if (error) {
userInfo[AFNetworkingTaskDidCompleteErrorKey] = error; dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
if (self.completionHandler) {
self.completionHandler(task.response, responseObject, error);
} dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
});
});
} else {
dispatch_async(url_session_manager_processing_queue(), ^{
NSError *serializationError = nil;
responseObject = [manager.responseSerializer responseObjectForResponse:task.response data:data error:&serializationError]; if (self.downloadFileURL) {
responseObject = self.downloadFileURL;
} if (responseObject) {
userInfo[AFNetworkingTaskDidCompleteSerializedResponseKey] = responseObject;
} if (serializationError) {
userInfo[AFNetworkingTaskDidCompleteErrorKey] = serializationError;
} dispatch_group_async(manager.completionGroup ?: url_session_manager_completion_group(), manager.completionQueue ?: dispatch_get_main_queue(), ^{
if (self.completionHandler) {
self.completionHandler(task.response, responseObject, serializationError);
} dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
});
});
});
}
#pragma clang diagnostic pop
}