iOS-AFNetworking之AFHTTPSessionManager详解

序言

AFNetworking2.0和3.0区别很大，也是因为苹果废弃了NSURLConnection，而改用了NSURLSession，AFNetworking3.0实际上只是对NSURLSession所做的操作进行了高度封装，提供更加简洁的API供编码调用。

查看AFHTTPSessionManager.h文件，可知AFHTTPSessionManager是AFURLSessionManager的子类：

@interface AFHTTPSessionManager : AFURLSessionManager

实例代码 - 下载一张图片

// 下载图片并且保存
- (void)downloadImgAndSave {
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    manager.responseSerializer = [AFHTTPResponseSerializer serializer];
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"image/jpeg", nil];
    
    __weak __typeof__(self) weakSelf = self;
    NSString *url = @"http://www.pptbz.com/pptpic/UploadFiles_6909/201203/2012031220134655.jpg";
    
    // 开始下载
    [manager GET:url parameters:nil progress:^(NSProgress *downloadProgress) {
        NSLog(@"progress:%lld",downloadProgress.completedUnitCount);
    } success:^(NSURLSessionDataTask *task, id responseObject) {
        NSLog(@"图片下载完成");
        __strong __typeof__(weakSelf) strongSelf = weakSelf;
        strongSelf.imgView.image = [UIImage imageWithData:(NSData *)responseObject];
    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        if (error) {
            NSLog(@"%@",error.userInfo);
        }
    }];
}

运行结果

image.png

一 GET请求调用函数分析

AFHTTPSessionManager.m

- (NSURLSessionDataTask *)GET:(NSString *)URLString
                   parameters:(id)parameters
                     progress:(void (^)(NSProgress * _Nonnull))downloadProgress
                      success:(void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success
                      failure:(void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{

    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET"
                                                        URLString:URLString
                                                       parameters:parameters
                                                   uploadProgress:nil
                                                 downloadProgress:downloadProgress
                                                          success:success
                                                          failure:failure];

    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
                                       URLString:(NSString *)URLString
                                      parameters:(id)parameters
                                  uploadProgress:(nullable void (^)(NSProgress *uploadProgress)) uploadProgress
                                downloadProgress:(nullable void (^)(NSProgress *downloadProgress)) downloadProgress
                                         success:(void (^)(NSURLSessionDataTask *, id))success
                                         failure:(void (^)(NSURLSessionDataTask *, NSError *))failure
{
    NSError *serializationError = nil;
    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
    if (serializationError) {
        if (failure) {
            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
                failure(nil, serializationError);
            });
        }

        return nil;
    }

    __block NSURLSessionDataTask *dataTask = nil;
    dataTask = [self dataTaskWithRequest:request
                          uploadProgress:uploadProgress
                        downloadProgress:downloadProgress
                       completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
        if (error) {
            if (failure) {
                failure(dataTask, error);
            }
        } else {
            if (success) {
                success(dataTask, responseObject);
            }
        }
    }];

    return dataTask;
}

AFURLSessionManager.m

- (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;
}

二 AFN的GET和POST请求实现第二层 - AFURLSessionManager

实例代码 - 下载一个较大文件

// 下载一个大文件
- (void)downloadBigFile {
    // 1.创建配置参数
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    // 2.创建会话管理者
    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
    // 3.创建请求对象
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://dldir1.qq.com/qqfile/QQforMac/QQ_V5.4.0.dmg"]];
    
    // 4.创建下载任务
    /**
     * 第一个参数 - request：请求对象
     * 第二个参数 - progress：下载进度block
     *      其中： downloadProgress.completedUnitCount：已经完成的大小
     *            downloadProgress.totalUnitCount：文件的总大小
     * 第三个参数 - destination：自动完成文件剪切操作
     *      其中： 返回值:该文件应该被剪切到哪里
     *            targetPath：临时路径 tmp NSURL
     *            response：响应头
     * 第四个参数 - completionHandler：下载完成回调
     *      其中： filePath：真实路径 == 第三个参数的返回值
     *            error:错误信息
     */
    NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:^(NSProgress *downloadProgress) {
         __weak typeof(self) weakSelf = self;
        // 获取主线程，不然无法正确显示进度。
        NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
        [mainQueue addOperationWithBlock:^{
            weakSelf.progressLbe.text = [NSString stringWithFormat:@"当前下载进度:%.2f%%",100.0 * downloadProgress.completedUnitCount / downloadProgress.totalUnitCount];
        }];
    } destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {
        
        NSURL *path = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
        return [path URLByAppendingPathComponent:response.suggestedFilename];
        
    } completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {
        NSLog(@"File downloaded to: %@", filePath);
    }];
    
    // 5.开启下载任务
    [downloadTask resume];
}

运行结果

image.png

1.gif

内部封装分析 AFURLSessionManager.m

- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request
                                             progress:(void (^)(NSProgress *downloadProgress)) downloadProgressBlock
                                          destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination
                                    completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler
{
    __block NSURLSessionDownloadTask *downloadTask = nil;
    url_session_manager_create_task_safely(^{
        downloadTask = [self.session downloadTaskWithRequest:request];
    });

    [self addDelegateForDownloadTask:downloadTask progress:downloadProgressBlock destination:destination completionHandler:completionHandler];

    return downloadTask;
}

其中self.session是NSURLSession的一个实例对象，dataTaskWithRequest:是其创建任务的一个方式。

@property (readonly, nonatomic, strong) NSURLSession *session;

- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request;

添加代理的封装


- (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] initWithTask:downloadTask];
    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;
}

其中setDelegate:forTask的实现

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

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

其中mutableTaskDelegatesKeyedByTaskIdentifier是一个可变字典

@property (readwrite, nonatomic, strong) NSMutableDictionary *mutableTaskDelegatesKeyedByTaskIdentifier;

被调用的地方在

- (AFURLSessionManagerTaskDelegate *)delegateForTask:(NSURLSessionTask *)task {
    NSParameterAssert(task);

    AFURLSessionManagerTaskDelegate *delegate = nil;
    [self.lock lock];
    delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)];
    [self.lock unlock];

    return delegate;
}

进而调用的是系统的代理

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location
{
    AFURLSessionManagerTaskDelegate *delegate = [self delegateForTask:downloadTask];
    if (self.downloadTaskDidFinishDownloading) {
        NSURL *fileURL = self.downloadTaskDidFinishDownloading(session, downloadTask, location);
        if (fileURL) {
            delegate.downloadFileURL = fileURL;
            NSError *error = nil;
            
            if (![[NSFileManager defaultManager] moveItemAtURL:location toURL:fileURL error:&error]) {
                [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidFailToMoveFileNotification object:downloadTask userInfo:error.userInfo];
            }

            return;
        }
    }

    if (delegate) {
        [delegate URLSession:session downloadTask:downloadTask didFinishDownloadingToURL:location];
    }
}

在系统NSURLSessionDelegate回调方法中，下面方法被调用多次，即将任务作为key，从字典中取出对应的delegate，再回调出去，最终回调到应用层面。

我们看看AFURLSessionManager的方法目录结构就知道了

下图是NSURLSessionDelegate方法目录结构

image.png

下图是AFURLSessionDelegate方法目录结构，和系统的NSURLSessionDelegate很像，别弄混了。

image.png

三 dataTaskWithRequest:completionHandler:函数详解

说明：这个NSURLSession的API容易跟AFURLSessionManager的API混淆，参数都是一个request和一个handler block。

NSURLSession的API是这样的

- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                            completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))completionHandler;

而AFURLSessionManager的API是这样的

- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                            completionHandler:(void (^)(NSURLResponse *response, id responseObject,  NSError * error))completionHandler DEPRECATED_ATTRIBUTE;

实例代码

// 下载任务执行块
- (void)dataTaskWithRequest {
    // 下载地址
    NSURL *url = [NSURL URLWithString:@"http://dldir1.qq.com/qqfile/QQforMac/QQ_V5.4.0.dmg"];
    // 创建request请求
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    // 设置HTTP请求头中的Range
    NSString *range = [NSString stringWithFormat:@"bytes=%zd-", self.currentLength];
    [request setValue:range forHTTPHeaderField:@"Range"];
    
    // 开始下载任务
    __weak typeof(self) weakSelf = self;
    NSURLSessionDataTask *downloadTask = [self.manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
        // 下载完成
        // 清空长度
        weakSelf.currentLength = 0;
        weakSelf.fileLength = 0;
        
        // 关闭fileHandle
        [weakSelf.fileHandle closeFile];
        weakSelf.fileHandle = nil;
    }];
}

其中manager是懒加载得到的

- (AFURLSessionManager *)manager {
    if (_manager == nil) {
        _manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
    }
    return _manager;
}

AF内部封装实现

- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request
                            completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    return [self dataTaskWithRequest:request uploadProgress:nil downloadProgress:nil completionHandler:completionHandler];
}

- (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;
}

四总结

AF请求操作内部实现也是和原生NSURLSession操作一样，创建task，调用resume发送请求。

项目连接地址 - AFNetworkingDemo

iOS-AFNetworking之AFHTTPSessionManager详解

序言

一 GET请求调用函数分析

二 AFN的GET和POST请求实现第二层 - AFURLSessionManager

三 dataTaskWithRequest:completionHandler:函数详解

四 总结

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四总结