第25月第26天 dispatch_group_t dispatch_semaphore_t

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
}