AFNetworking 概述

NSURLSession 初始化 创建 管理

- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration {
    self = [super init];
    if (!self) {
        return nil;
    }

    if (!configuration) {
        configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    }

    self.sessionConfiguration = configuration;

    self.operationQueue = [[NSOperationQueue alloc] init];
    self.operationQueue.maxConcurrentOperationCount = 1;

    self.session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:self.operationQueue];

    self.responseSerializer = [AFJSONResponseSerializer serializer];

    self.securityPolicy = [AFSecurityPolicy defaultPolicy];

#if !TARGET_OS_WATCH
    self.reachabilityManager = [AFNetworkReachabilityManager sharedManager];
#endif

    self.mutableTaskDelegatesKeyedByTaskIdentifier = [[NSMutableDictionary alloc] init];

    self.lock = [[NSLock alloc] init];
    self.lock.name = AFURLSessionManagerLockName;

    [self.session getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) {
        for (NSURLSessionDataTask *task in dataTasks) {
            [self addDelegateForDataTask:task uploadProgress:nil downloadProgress:nil completionHandler:nil];
        }

        for (NSURLSessionUploadTask *uploadTask in uploadTasks) {
            [self addDelegateForUploadTask:uploadTask progress:nil completionHandler:nil];
        }

        for (NSURLSessionDownloadTask *downloadTask in downloadTasks) {
            [self addDelegateForDownloadTask:downloadTask progress:nil destination:nil completionHandler:nil];
        }
    }];

    return self;
}

1. NSURLSessionConfiguration 初始化 defaultSessionConfiguration类型
2. NSURLSession 初始化 设置了代理 代理队列
3. 初始化 AFJSONResponseSerializer(响应序列化) AFSecurityPolicy(安全认证) AFNetworkReachabilityManager(网络状态监听)
4. 初始化一个字典用来保存task

NSURLSessionTask

NSURLSessionTask

- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                               uploadProgress:(nullable void (^)(NSProgress *uploadProgress)) uploadProgressBlock
                             downloadProgress:(nullable void (^)(NSProgress *downloadProgress)) downloadProgressBlock
                            completionHandler:(nullable void (^)(NSURLResponse *response, id _Nullable responseObject,  NSError * _Nullable error))completionHandler {

    __block NSURLSessionDataTask *dataTask = nil;
    url_session_manager_create_task_safely(^{
        dataTask = [self.session dataTaskWithRequest:request];
    });

    [self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler];

    return dataTask;
}

1. 传入request 然后session调用dataTaskWithRequest 然后data task
2. task和返回block 进行设置管理
3. 返回task

- (void)addDelegateForDataTask:(NSURLSessionDataTask *)dataTask
                uploadProgress:(nullable void (^)(NSProgress *uploadProgress)) uploadProgressBlock
              downloadProgress:(nullable void (^)(NSProgress *downloadProgress)) downloadProgressBlock
             completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    AFURLSessionManagerTaskDelegate *delegate = [[AFURLSessionManagerTaskDelegate alloc] init];
    delegate.manager = self;
    delegate.completionHandler = completionHandler;

    dataTask.taskDescription = self.taskDescriptionForSessionTasks;
    [self setDelegate:delegate forTask:dataTask];

    delegate.uploadProgressBlock = uploadProgressBlock;
    delegate.downloadProgressBlock = downloadProgressBlock;
}

- (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate
            forTask:(NSURLSessionTask *)task
{
    NSParameterAssert(task);
    NSParameterAssert(delegate);

    [self.lock lock];
    self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
    [delegate setupProgressForTask:task];
    [self addNotificationObserverForTask:task];
    [self.lock unlock];
}

1. 使用字典mutableTaskDelegatesKeyedByTaskIdentifier来存储task

NSURLSession的那些delegate

@interface AFURLSessionManager : NSObject <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate, NSSecureCoding, NSCopying>

1. 在初始化的时候 把NSURLSession的代理设置为self
2. 实现代理的方法 提供block

@protocol NSURLSessionDelegate <NSObject>
@optional

/* The last message a session receives.  A session will only become
 * invalid because of a systemic error or when it has been
 * explicitly invalidated, in which case the error parameter will be nil.
 */

当前这个session已经失效时，该代理方法被调用。

- (void)URLSession:(NSURLSession *)session didBecomeInvalidWithError:(nullable NSError *)error;

/**
 Sets a block to be executed when the managed session becomes invalid, as handled by the `NSURLSessionDelegate` method `URLSession:didBecomeInvalidWithError:`.

 @param block A block object to be executed when the managed session becomes invalid. The block has no return value, and takes two arguments: the session, and the error related to the cause of invalidation.
 */
- (void)setSessionDidBecomeInvalidBlock:(nullable void (^)(NSURLSession *session, NSError *error))block;

- (void)setSessionDidBecomeInvalidBlock:(void (^)(NSURLSession *session, NSError *error))block {
    self.sessionDidBecomeInvalid = block;
}

#pragma mark - NSURLSessionDelegate

- (void)URLSession:(NSURLSession *)session
didBecomeInvalidWithError:(NSError *)error
{
    if (self.sessionDidBecomeInvalid) {
        self.sessionDidBecomeInvalid(session, error);
    }

    [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDidInvalidateNotification object:session];
}

小结：

1. AFURLSessionManager是对NSURLSession的封装
2. AFURLSessionManager dataTaskWithRequest创建返回task
3. mutableTaskDelegatesKeyedByTaskIdentifier 字典用来管理task
4. 传入的block 在合适的时机被调用
5. 代理方法也提供block接口