1.
dispatch_group_enter(group);
dispatch_group_leave(group);
dispatch_group_notify(group1, queue1,block);
在這種組合下，根據任務是同步、異步又分為兩種，這兩種組合的執行代碼與運作結果如下：
第一種：同步任務時
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(@"%@-同步任務執行-:%ld",@"任務1",(long)i);
}
dispatch_group_leave(group2);
});
dispatch_group_enter(group2);
dispatch_sync(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-同步任務執行-:%ld",@"任務2",(long)i);
}
dispatch_group_leave(group2);
});
// //等待上面的任務全部完成後，會往下繼續執行 （會阻塞目前線程）
// dispatch_group_wait(group2, DISPATCH_TIME_FOREVER);
//等待上面的任務全部完成後，會收到通知執行block中的代碼 （不會阻塞線程）
dispatch_group_notify(group2, queue2, ^{
NSLog(@"Method2-全部任務執行完成");
}); 同步任務執行結果：
第二種：異步任務時
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(@"%@-異步任務執行-:%ld",@"任務1",(long)i);
}
dispatch_group_leave(group2);
});
dispatch_group_enter(group2);
dispatch_async(queue2, ^{
for (NSInteger i =0; i<3; i++) {
sleep(1);
NSLog(@"%@-異步任務執行-:%ld",@"任務2",(long)i);
}
dispatch_group_leave(group2);
});
// //等待上面的任務全部完成後，會往下繼續執行 （會阻塞目前線程）
// dispatch_group_wait(group2, DISPATCH_TIME_FOREVER);
//等待上面的任務全部完成後，會收到通知執行block中的代碼 （不會阻塞線程）
dispatch_group_notify(group2, queue2, ^{
NSLog(@"Method2-全部任務執行完成");
}); 異步任務執行結果：
AAA2.
建立一個信号量，作為全局變量。
并初始化，信号量為0
dispatch_semaphore_t semaphore;
semaphore = dispatch_semaphore_create(0);
建立一個dispatch_group_t，開啟兩個組異步線程（dispatch_group_async），分别執行兩個網絡請求。
一個組通知線程（dispatch_group_notify），用于接收前面兩個線程的結果。
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];//請求1
});
dispatch_group_async(group, queue, ^{
[weakSelf loadRelationReward];//請求2
});
dispatch_group_notify(group, queue, ^{
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
//合并（此處是資料處理，你可根據具體業務需求進行處理）
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;
}
//有資料重新整理
if (weakSelf.sumArr.count > 0) {
//在主線程重新整理頁面
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf initTableView];
});
}
}); 3.afnetworking
為每一個NSURLSessionDownloadTask建立AFURLSessionManagerTaskDelegate，把請求的completionHandler也放在delegate。
從統一的回調didCompleteWithError到delegate的didCompleteWithError，再調用completionHandler傳回。
- (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];
...
//需要加鎖
- (AFURLSessionManagerTaskDelegate *)delegateForTask:(NSURLSessionTask *)task {
NSParameterAssert(task);
AFURLSessionManagerTaskDelegate *delegate = nil;
[self.lock lock];
delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)];
[self.lock unlock];
return delegate;
}
...
//每一個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
} ![HDU 6232 Confliction[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)