原创 -- 我对AF的理解-AFURLSessionManager.m

 这个是网络请求方法调用的顺序。**改为99

2020-06-10

最近在看SVProgressHUD，一头雾水。

又回头看了看AF找找自信，把我这边博客找出来看看（其实写的不好）。看完之后有些感慨要发下，不然会憋出内伤的。

刚开始看AF，也是一头雾水。无从下手最能体现我当时的现状，看看懂然后百度，谷歌查AF源码解读，放到一边不管不问。如此循环，我就想着自己不是开发的料，第三方开源都看不出点啥东西。如果不是生活我本来就不想再看Af，可是看到招聘写的技能要求，我就又狠心看一遍，反正是被虐的怀疑人生。但是我还是给每次看到新的知识加注释，就这样我慢慢发现Af也是能够看懂了（只是心理知道他的逻辑调用）。然后出了问题知道怎么取查问题！！希望自己坚持把svp整理出来吧。 

2020-05-25

线程调用顺序

这里 #0 #1 #2 #3 #4 #5 #6  #7 都是线程

#0	 -[AFURLSessionManager addNotificationObserverForTask:] 
#1	 -[AFURLSessionManager setDelegate:forTask:] 
#2	 -[AFURLSessionManager addDelegateForDataTask:uploadProgress:downloadProgress:completionHandler:] 
#3	 -[AFURLSessionManager dataTaskWithRequest:uploadProgress:downloadProgress:completionHandler:] 
#4	 -[AFHTTPSessionManager dataTaskWithHTTPMethod:URLString:parameters:headers:uploadProgress:downloadProgress:success:failure:] 
#5	 -[AFHTTPSessionManager POST:parameters:headers:progress:success:failure:] 
#6	 -[ZLJNetViewController postNetWorking] 
#7	 -[ZLJNetViewController touchesBegan:withEvent:] 

　

#7 我添加的点击方法

#6 我自己写的pos请求

#5 这个线程是被线程#6调用的方法 -- 添加请求类型-POST，其他都在#4中处理。#4会返回一个dataTask(NSURLSessionDataTask)

#4 是线程#5调用的方法 -- 1.构建请求NSMutableURLRequest (其他设置)   2.请求回来的数据处理，用block(completionHandler:^(......))处理失败/成功数据。reques/uploadProgress/downloadProgress交给#3处理,#3返回dataTask

#3 是线程#4调用的方法 -- 没做实事，交给#2做处理。创建dataTask对象。

#2 是线程#3调用的方法 -- 1.manager（AFURLSessionManager）和delegate(AFURLSessionManagerTaskDelegate)进行关联（网上看到的解释）。给manager设置delegate。上传/下载block赋值。

#1 是线程#2调用的方法 -- 根据task发通知出去（2个通知）

#0 是线程#1调用的方法 -- 发出2个通知1.开始请求(taskDidResume)，2.暂停请求(taskDidSuspend)。

****************************************************************************************************** 

上面处理完成之后，线程#5中的 dataTask调用方法[dataTask resume];//开始请求

请求之后在delegate方法中有返回结果。 这个是系统delegate方法 --请求结束或失败时调用

#0	-[AFURLSessionManagerTaskDelegate URLSession:task:didCompleteWithError:] 

　　

2020-05-23

#pragma mark -- POST
- (void)postNetWorking{//1
    NSString    *urlString = [NSString stringWithFormat:@"/cgi-bin/courseDetail_json?course_id=52**3"];
    NSURL *baseUrl = [NSURL URLWithString:@"http://ke.qq.com/"];
    AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc] initWithBaseURL:baseUrl];
    manager.responseSerializer = [AFJSONResponseSerializer serializer];
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"application/json"];
     NSLog(@"zlj--当前输出A1：%s",__FUNCTION__);
    [manager POST:urlString parameters:nil headers:nil progress:^(NSProgress * _Nonnull uploadProgress) {
        NSLog(@"downloadProgress --- ：%s",__FUNCTION__);
    } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
        NSLog(@"zlj--当前输出success：%s",__FUNCTION__);
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        NSLog(@"zlj--当前输出failure：%s",__FUNCTION__);
    }];
}

　　

1.AFHTTPSessionManager ： AFURLSessionManager

1- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
                             parameters:(nullable id)parameters
                                headers:(nullable NSDictionary <NSString *, NSString *> *)headers
                               progress:(nullable void (^)(NSProgress *uploadProgress))uploadProgress
                                success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                                failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure
{

2- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
                                       URLString:(NSString *)URLString
                                      parameters:(nullable id)parameters
                                         headers:(nullable NSDictionary <NSString *, NSString *> *)headers
                                  uploadProgress:(nullable void (^)(NSProgress *uploadProgress)) uploadProgress
                                downloadProgress:(nullable void (^)(NSProgress *downloadProgress)) downloadProgress
                                         success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                                         failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure
{

2.AFURLSessionManager

3- (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 {

4- (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
{

5- (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate
            forTask:(NSURLSessionTask *)task
{//7
    NSLog(@"zlj--当前输出A10：%s",__FUNCTION__);
    NSParameterAssert(task);
    NSParameterAssert(delegate);
    [self.lock lock];
    self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
    [self addNotificationObserverForTask:task];
    [self.lock unlock];
}
6
- (void)addNotificationObserverForTask:(NSURLSessionTask *)task {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(taskDidResume:) name:AFNSURLSessionTaskDidResumeNotification object:task];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(taskDidSuspend:) name:AFNSURLSessionTaskDidSuspendNotification object:task];
}

　　

@interface _AFURLSessionTaskSwizzling : NSObject
@end

这个类是发出通知（上面的2个通知），

ps:现在不知道的就是，这个类 +laod{}是什么时候调用的。2020-05-23

　　

/***************************************************************************************************************** 分割线  *******************************************************************************************/

@interface AFURLSessionManagerTaskDelegate : NSObject <NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>


@interface _AFURLSessionTaskSwizzling : NSObject


@interface AFURLSessionManager ()

　　

这个文件里面有三个 @interface，真是让我大吃一惊。不弄死死真难平我心头之恨！！！草 

　　

static dispatch_queue_t url_session_manager_processing_queue() {
    static dispatch_queue_t af_url_session_manager_processing_queue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
            //会话管理处理队列
        af_url_session_manager_processing_queue = dispatch_queue_create("com.alamofire.networking.session.manager.processing", DISPATCH_QUEUE_CONCURRENT);
    });

    return af_url_session_manager_processing_queue;
}

static dispatch_group_t url_session_manager_completion_group() {
    static dispatch_group_t af_url_session_manager_completion_group;//会话管理完成
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        af_url_session_manager_completion_group = dispatch_group_create();
    });

    return af_url_session_manager_completion_group;
}

　　开头2个C函数，蒙了不知道啥意思！！！！

NSString * const AFNetworkingTaskDidResumeNotification = @"com.alamofire.networking.task.resume";
NSString * const AFNetworkingTaskDidCompleteNotification = @"com.alamofire.networking.task.complete";
NSString * const AFNetworkingTaskDidSuspendNotification = @"com.alamofire.networking.task.suspend";
NSString * const AFURLSessionDidInvalidateNotification = @"com.alamofire.networking.session.invalidate";
NSString * const AFURLSessionDownloadTaskDidMoveFileSuccessfullyNotification = @"com.alamofire.networking.session.download.file-manager-succeed";
NSString * const AFURLSessionDownloadTaskDidFailToMoveFileNotification = @"com.alamofire.networking.session.download.file-manager-error";

NSString * const AFNetworkingTaskDidCompleteSerializedResponseKey = @"com.alamofire.networking.task.complete.serializedresponse";
NSString * const AFNetworkingTaskDidCompleteResponseSerializerKey = @"com.alamofire.networking.task.complete.responseserializer";
NSString * const AFNetworkingTaskDidCompleteResponseDataKey = @"com.alamofire.networking.complete.finish.responsedata";
NSString * const AFNetworkingTaskDidCompleteErrorKey = @"com.alamofire.networking.task.complete.error";
NSString * const AFNetworkingTaskDidCompleteAssetPathKey = @"com.alamofire.networking.task.complete.assetpath";
NSString * const AFNetworkingTaskDidCompleteSessionTaskMetrics = @"com.alamofire.networking.complete.sessiontaskmetrics";

static NSString * const AFURLSessionManagerLockName = @"com.alamofire.networking.session.manager.lock";

typedef void (^AFURLSessionDidBecomeInvalidBlock)(NSURLSession *session, NSError *error);
typedef NSURLSessionAuthChallengeDisposition (^AFURLSessionDidReceiveAuthenticationChallengeBlock)(NSURLSession *session, NSURLAuthenticationChallenge *challenge, NSURLCredential * __autoreleasing *credential);

typedef NSURLRequest * (^AFURLSessionTaskWillPerformHTTPRedirectionBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLResponse *response, NSURLRequest *request);
typedef NSURLSessionAuthChallengeDisposition (^AFURLSessionTaskDidReceiveAuthenticationChallengeBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLAuthenticationChallenge *challenge, NSURLCredential * __autoreleasing *credential);
typedef id (^AFURLSessionTaskAuthenticationChallengeBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLAuthenticationChallenge *challenge, void (^completionHandler)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential));
typedef void (^AFURLSessionDidFinishEventsForBackgroundURLSessionBlock)(NSURLSession *session);

typedef NSInputStream * (^AFURLSessionTaskNeedNewBodyStreamBlock)(NSURLSession *session, NSURLSessionTask *task);
typedef void (^AFURLSessionTaskDidSendBodyDataBlock)(NSURLSession *session, NSURLSessionTask *task, int64_t bytesSent, int64_t totalBytesSent, int64_t totalBytesExpectedToSend);
typedef void (^AFURLSessionTaskDidCompleteBlock)(NSURLSession *session, NSURLSessionTask *task, NSError *error);
#if AF_CAN_INCLUDE_SESSION_TASK_METRICS
typedef void (^AFURLSessionTaskDidFinishCollectingMetricsBlock)(NSURLSession *session, NSURLSessionTask *task, NSURLSessionTaskMetrics * metrics) AF_API_AVAILABLE(ios(10), macosx(10.12), watchos(3), tvos(10));
#endif

typedef NSURLSessionResponseDisposition (^AFURLSessionDataTaskDidReceiveResponseBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSURLResponse *response);
typedef void (^AFURLSessionDataTaskDidBecomeDownloadTaskBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSURLSessionDownloadTask *downloadTask);
typedef void (^AFURLSessionDataTaskDidReceiveDataBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSData *data);
typedef NSCachedURLResponse * (^AFURLSessionDataTaskWillCacheResponseBlock)(NSURLSession *session, NSURLSessionDataTask *dataTask, NSCachedURLResponse *proposedResponse);

typedef NSURL * (^AFURLSessionDownloadTaskDidFinishDownloadingBlock)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location);
typedef void (^AFURLSessionDownloadTaskDidWriteDataBlock)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite);
typedef void (^AFURLSessionDownloadTaskDidResumeBlock)(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, int64_t fileOffset, int64_t expectedTotalBytes);
typedef void (^AFURLSessionTaskProgressBlock)(NSProgress *);

typedef void (^AFURLSessionTaskCompletionHandler)(NSURLResponse *response, id responseObject, NSError *error);

　　这一堆，我只是知道通知用到，回调block用到。完

************************************************************   分割线来下，我需要你 第一个@interface  开始 *****************************************************************************

@interface AFURLSessionManagerTaskDelegate : NSObject <NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>
- (instancetype)initWithTask:(NSURLSessionTask *)task;
@property (nonatomic, weak) AFURLSessionManager *manager;//这个有用到
@property (nonatomic, strong) NSMutableData *mutableData;
@property (nonatomic, strong) NSProgress *uploadProgress;
@property (nonatomic, strong) NSProgress *downloadProgress;
@property (nonatomic, copy) NSURL *downloadFileURL;
#if AF_CAN_INCLUDE_SESSION_TASK_METRICS
@property (nonatomic, strong) NSURLSessionTaskMetrics *sessionTaskMetrics AF_API_AVAILABLE(ios(10), macosx(10.12), watchos(3), tvos(10));
#endif
@property (nonatomic, copy) AFURLSessionDownloadTaskDidFinishDownloadingBlock downloadTaskDidFinishDownloading;
@property (nonatomic, copy) AFURLSessionTaskProgressBlock uploadProgressBlock;
@property (nonatomic, copy) AFURLSessionTaskProgressBlock downloadProgressBlock;
@property (nonatomic, copy) AFURLSessionTaskCompletionHandler completionHandler;
@end

　　

- (void)dealloc {
        //在监听属性的时候、可以用NSStringFromSelector(@selector(xxx))这种方式来自动提示。 http://www.cocoachina.com/articles/27509
    [self.downloadProgress removeObserver:self forKeyPath:NSStringFromSelector(@selector(fractionCompleted))];
    [self.uploadProgress removeObserver:self forKeyPath:NSStringFromSelector(@selector(fractionCompleted))];
}

　　不说了。

#pragma mark - NSURLSessionTaskDelegate -- 系统delegate

- (void)URLSession:(__unused NSURLSession *)session
              task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
    NSLog(@"zlj--当前输出------------A1000 什么时候调用：%s",__FUNCTION__);
    error = objc_getAssociatedObject(task, AuthenticationChallengeErrorKey) ?: error;//不知道什么意思
    __strong AFURLSessionManager *manager = self.manager;
    __block id responseObject = nil;
    /*
     (lldb) po userInfo
     {
     "com.alamofire.networking.task.complete.responseserializer" = "<AFJSONResponseSerializer: 0x600002ed1350>";
     }
     */
    NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
    userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer;//eg, AFJSONResponseSerializer
        //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 AF_CAN_USE_AT_AVAILABLE && AF_CAN_INCLUDE_SESSION_TASK_METRICS
    if (@available(iOS 10, macOS 10.12, watchOS 3, tvOS 10, *)) {
        if (self.sessionTaskMetrics) {
            userInfo[AFNetworkingTaskDidCompleteSessionTaskMetrics] = self.sessionTaskMetrics;
        }
    }
#endif
    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;
            }

            /**

             这个目的是返回网络请求结束之后返回数据，
             completionGroup：这个是.h中声明的属性，全局搜索没有找到赋值语句，猜测（如果程序员自己创建，就自己处理）这里是AF自己处理，
             然后再发个通知出去，网络请求完成了，接下来该怎样就怎么。

             */
            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];
                });
            });
        });
    }
}

#if AF_CAN_INCLUDE_SESSION_TASK_METRICS
- (void)URLSession:(NSURLSession *)session
              task:(NSURLSessionTask *)task
didFinishCollectingMetrics:(NSURLSessionTaskMetrics *)metrics AF_API_AVAILABLE(ios(10), macosx(10.12), watchos(3), tvos(10)) {
    self.sessionTaskMetrics = metrics;
}
#endif

　　

　　kvo监听到了什么

#pragma mark - NSURLSessionDataDelegate

- (void)URLSession:(__unused NSURLSession *)session
          dataTask:(__unused NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data
{
    self.downloadProgress.totalUnitCount = dataTask.countOfBytesExpectedToReceive;
    self.downloadProgress.completedUnitCount = dataTask.countOfBytesReceived;

    [self.mutableData appendData:data];
}

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
   didSendBodyData:(int64_t)bytesSent
    totalBytesSent:(int64_t)totalBytesSent
totalBytesExpectedToSend:(int64_t)totalBytesExpectedToSend{

    self.uploadProgress.totalUnitCount = task.countOfBytesExpectedToSend;
    self.uploadProgress.completedUnitCount = task.countOfBytesSent;
}

　　请求数据什么吧

#pragma mark - NSURLSessionDownloadDelegate

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite{

    self.downloadProgress.totalUnitCount = totalBytesExpectedToWrite;
    self.downloadProgress.completedUnitCount = totalBytesWritten;
}

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
 didResumeAtOffset:(int64_t)fileOffset
expectedTotalBytes:(int64_t)expectedTotalBytes{

    self.downloadProgress.totalUnitCount = expectedTotalBytes;
    self.downloadProgress.completedUnitCount = fileOffset;
}

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location
{
    self.downloadFileURL = nil;

    if (self.downloadTaskDidFinishDownloading) {
        self.downloadFileURL = self.downloadTaskDidFinishDownloading(session, downloadTask, location);
        if (self.downloadFileURL) {
            NSError *fileManagerError = nil;

            if (![[NSFileManager defaultManager] moveItemAtURL:location toURL:self.downloadFileURL error:&fileManagerError]) {
                [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidFailToMoveFileNotification object:downloadTask userInfo:fileManagerError.userInfo];
            } else {
                [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidMoveFileSuccessfullyNotification object:downloadTask userInfo:nil];
            }
        }
    }
}

@end

　　下载数据

************************************************************   分割线来下，我需要你 第二个@interface 开始  *****************************************************************************

static inline void af_swizzleSelector(Class theClass, SEL originalSelector, SEL swizzledSelector) {
    Method originalMethod = class_getInstanceMethod(theClass, originalSelector);
    Method swizzledMethod = class_getInstanceMethod(theClass, swizzledSelector);
    method_exchangeImplementations(originalMethod, swizzledMethod);
}

static inline BOOL af_addMethod(Class theClass, SEL selector, Method method) {
    return class_addMethod(theClass, selector,  method_getImplementation(method),  method_getTypeEncoding(method));
}

static NSString * const AFNSURLSessionTaskDidResumeNotification  = @"com.alamofire.networking.nsurlsessiontask.resume";
static NSString * const AFNSURLSessionTaskDidSuspendNotification = @"com.alamofire.networking.nsurlsessiontask.suspend";

　　先做个准备

@implementation _AFURLSessionTaskSwizzling

+ (void)load {
    /**
     WARNING: Trouble Ahead
     https://github.com/AFNetworking/AFNetworking/pull/2702
     */

    if (NSClassFromString(@"NSURLSessionTask")) {
        /**
         iOS 7 and iOS 8 differ in NSURLSessionTask implementation, which makes the next bit of code a bit tricky.
         Many Unit Tests have been built to validate as much of this behavior has possible.
         Here is what we know:
         - NSURLSessionTasks are implemented with class clusters, meaning the class you request from the API isn't actually the type of class you will get back.
         - Simply referencing `[NSURLSessionTask class]` will not work. You need to ask an `NSURLSession` to actually create an object, and grab the class from there.
         - On iOS 7, `localDataTask` is a `__NSCFLocalDataTask`, which inherits from `__NSCFLocalSessionTask`, which inherits from `__NSCFURLSessionTask`.
         - On iOS 8, `localDataTask` is a `__NSCFLocalDataTask`, which inherits from `__NSCFLocalSessionTask`, which inherits from `NSURLSessionTask`.
         - On iOS 7, `__NSCFLocalSessionTask` and `__NSCFURLSessionTask` are the only two classes that have their own implementations of `resume` and `suspend`, and `__NSCFLocalSessionTask` DOES NOT CALL SUPER. This means both classes need to be swizzled.
         - On iOS 8, `NSURLSessionTask` is the only class that implements `resume` and `suspend`. This means this is the only class that needs to be swizzled.
         - Because `NSURLSessionTask` is not involved in the class hierarchy for every version of iOS, its easier to add the swizzled methods to a dummy class and manage them there.

         Some Assumptions:
         - No implementations of `resume` or `suspend` call super. If this were to change in a future version of iOS, we'd need to handle it.
         - No background task classes override `resume` or `suspend`
         
         The current solution:
         1) Grab an instance of `__NSCFLocalDataTask` by asking an instance of `NSURLSession` for a data task.
         2) Grab a pointer to the original implementation of `af_resume`
         3) Check to see if the current class has an implementation of resume. If so, continue to step 4.
         4) Grab the super class of the current class.
         5) Grab a pointer for the current class to the current implementation of `resume`.
         6) Grab a pointer for the super class to the current implementation of `resume`.
         7) If the current class implementation of `resume` is not equal to the super class implementation of `resume` AND the current implementation of `resume` is not equal to the original implementation of `af_resume`, THEN swizzle the methods
         8) Set the current class to the super class, and repeat steps 3-8
         */
        NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration ephemeralSessionConfiguration];
        NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration];
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnonnull"
        NSURLSessionDataTask *localDataTask = [session dataTaskWithURL:nil];
#pragma clang diagnostic pop
        IMP originalAFResumeIMP = method_getImplementation(class_getInstanceMethod([self class], @selector(af_resume)));
        Class currentClass = [localDataTask class];
        
        while (class_getInstanceMethod(currentClass, @selector(resume))) {
            Class superClass = [currentClass superclass];
            IMP classResumeIMP = method_getImplementation(class_getInstanceMethod(currentClass, @selector(resume)));
            IMP superclassResumeIMP = method_getImplementation(class_getInstanceMethod(superClass, @selector(resume)));
            if (classResumeIMP != superclassResumeIMP &&
                originalAFResumeIMP != classResumeIMP) {
                [self swizzleResumeAndSuspendMethodForClass:currentClass];
            }
            currentClass = [currentClass superclass];
        }
        
        [localDataTask cancel];
        [session finishTasksAndInvalidate];
    }
}

+ (void)swizzleResumeAndSuspendMethodForClass:(Class)theClass {
    Method afResumeMethod = class_getInstanceMethod(self, @selector(af_resume));
    Method afSuspendMethod = class_getInstanceMethod(self, @selector(af_suspend));

    if (af_addMethod(theClass, @selector(af_resume), afResumeMethod)) {
        af_swizzleSelector(theClass, @selector(resume), @selector(af_resume));
    }

    if (af_addMethod(theClass, @selector(af_suspend), afSuspendMethod)) {
        af_swizzleSelector(theClass, @selector(suspend), @selector(af_suspend));
    }
}

- (NSURLSessionTaskState)state {
    NSAssert(NO, @"State method should never be called in the actual dummy class");
    return NSURLSessionTaskStateCanceling;
}

- (void)af_resume {
    NSAssert([self respondsToSelector:@selector(state)], @"Does not respond to state");
    NSURLSessionTaskState state = [self state];
    [self af_resume];
    
    if (state != NSURLSessionTaskStateRunning) {
        [[NSNotificationCenter defaultCenter] postNotificationName:AFNSURLSessionTaskDidResumeNotification object:self];
    }
}

- (void)af_suspend {
    NSAssert([self respondsToSelector:@selector(state)], @"Does not respond to state");
    NSURLSessionTaskState state = [self state];
    [self af_suspend];
    
    if (state != NSURLSessionTaskStateSuspended) {
        [[NSNotificationCenter defaultCenter] postNotificationName:AFNSURLSessionTaskDidSuspendNotification object:self];
    }
}
@end

　　只是知道交换了实现方法，af_resume/resume ,af_suspend/suspend;

************************************************************   分割线来下，我需要你 第三个@interface 开始  *****************************************************************************

@interface AFURLSessionManager ()
@property (readwrite, nonatomic, strong) NSURLSessionConfiguration *sessionConfiguration;
@property (readwrite, nonatomic, strong) NSOperationQueue *operationQueue;
@property (readwrite, nonatomic, strong) NSURLSession *session;
@property (readwrite, nonatomic, strong) NSMutableDictionary *mutableTaskDelegatesKeyedByTaskIdentifier;
@property (readonly, nonatomic, copy) NSString *taskDescriptionForSessionTasks;
@property (readwrite, nonatomic, strong) NSLock *lock;
@property (readwrite, nonatomic, copy) AFURLSessionDidBecomeInvalidBlock sessionDidBecomeInvalid;
@property (readwrite, nonatomic, copy) AFURLSessionDidReceiveAuthenticationChallengeBlock sessionDidReceiveAuthenticationChallenge;
@property (readwrite, nonatomic, copy) AFURLSessionDidFinishEventsForBackgroundURLSessionBlock didFinishEventsForBackgroundURLSession AF_API_UNAVAILABLE(macos);
@property (readwrite, nonatomic, copy) AFURLSessionTaskWillPerformHTTPRedirectionBlock taskWillPerformHTTPRedirection;
@property (readwrite, nonatomic, copy) AFURLSessionTaskAuthenticationChallengeBlock authenticationChallengeHandler;
@property (readwrite, nonatomic, copy) AFURLSessionTaskNeedNewBodyStreamBlock taskNeedNewBodyStream;
@property (readwrite, nonatomic, copy) AFURLSessionTaskDidSendBodyDataBlock taskDidSendBodyData;
@property (readwrite, nonatomic, copy) AFURLSessionTaskDidCompleteBlock taskDidComplete;
#if AF_CAN_INCLUDE_SESSION_TASK_METRICS
@property (readwrite, nonatomic, copy) AFURLSessionTaskDidFinishCollectingMetricsBlock taskDidFinishCollectingMetrics AF_API_AVAILABLE(ios(10), macosx(10.12), watchos(3), tvos(10));
#endif
@property (readwrite, nonatomic, copy) AFURLSessionDataTaskDidReceiveResponseBlock dataTaskDidReceiveResponse;
@property (readwrite, nonatomic, copy) AFURLSessionDataTaskDidBecomeDownloadTaskBlock dataTaskDidBecomeDownloadTask;
@property (readwrite, nonatomic, copy) AFURLSessionDataTaskDidReceiveDataBlock dataTaskDidReceiveData;
@property (readwrite, nonatomic, copy) AFURLSessionDataTaskWillCacheResponseBlock dataTaskWillCacheResponse;
@property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidFinishDownloadingBlock downloadTaskDidFinishDownloading;
@property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidWriteDataBlock downloadTaskDidWriteData;
@property (readwrite, nonatomic, copy) AFURLSessionDownloadTaskDidResumeBlock downloadTaskDidResume;
@end

　　一通定义，block使用。

写不下去了，改天写！！