【iOS开发】 —— AFNetWorking源码（一）

简介

AFNetworking是适用于iOS，macOS，watchOS和tvOS的的网络库。它构建于Foundation URL系统之上，扩展了Cocoa内置的强大的高级网络抽象。它采用模块化架构，设计精良，功能丰富的API，使用起来非常简单。

组织架构图

通讯核心类

AFHTTPSessionManager

简介

AFHTTPSessionManager本身是对网络请求做了一些简单的封装，请求的整个逻辑是分发给AFURLSessionManager或者其他类去做的；其内部管理自己的两种序列化工具，用来对请求和响应的数据做序列化；同时依赖于父类提供的保证安全，监控网络状态，实现发出HTTP请求的核心功能；

属性和接口

模块一：创建AFHTTPSessionManager对象

在这里的manager创建AFHTTPSessionManager对象，不是单例。

+ (instancetype)manager {
    return [[[self class] alloc] initWithBaseURL:nil];
}

模块二：初始化该对象

//使用指定的URL初始化对象
- (instancetype)init {
    return [self initWithBaseURL:nil];
}

- (instancetype)initWithBaseURL:(NSURL *)url {
    return [self initWithBaseURL:url sessionConfiguration:nil];
}

- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration {
    return [self initWithBaseURL:nil sessionConfiguration:configuration];
}

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

    // 确保baseURL路径的终端斜杠，以便NSURL+URLWithString:relativeToURL：按预期工作
    if ([[url path] length] > 0 && ![[url absoluteString] hasSuffix:@"/"]) {
        url = [url URLByAppendingPathComponent:@""];
    }

    self.baseURL = url;
	// 默认HTTP请求序列化器和JSON响应序列化器
    self.requestSerializer = [AFHTTPRequestSerializer serializer];
    self.responseSerializer = [AFJSONResponseSerializer serializer];

    return self;
}

模块三：

- (void)setRequestSerializer:(AFHTTPRequestSerializer <AFURLRequestSerialization> *)requestSerializer {
    NSParameterAssert(requestSerializer);

    _requestSerializer = requestSerializer;
}

- (void)setResponseSerializer:(AFHTTPResponseSerializer <AFURLResponseSerialization> *)responseSerializer {
    NSParameterAssert(responseSerializer);

    [super setResponseSerializer:responseSerializer];
}

模块四：网络请求

大部分网络请求都是生成一个dataTask任务，调用resume开启请求。
有7种方式。

1. HEAD网络请求

- (NSURLSessionDataTask *)HEAD:(NSString *)URLString
                    parameters:(nullable id)parameters
                       headers:(nullable NSDictionary<NSString *,NSString *> *)headers
                       success:(nullable void (^)(NSURLSessionDataTask * _Nonnull))success
                       failure:(nullable void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"HEAD" URLString:URLString parameters:parameters headers:headers uploadProgress:nil downloadProgress:nil success:^(NSURLSessionDataTask *task, __unused id responseObject) {
        if (success) {
            success(task);
        }
    } failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

2. GET网络请求

- (NSURLSessionDataTask *)GET:(NSString *)URLString
                   parameters:(nullable id)parameters
                      headers:(nullable NSDictionary <NSString *, NSString *> *)headers
                     progress:(nullable void (^)(NSProgress * _Nonnull))downloadProgress
                      success:(nullable void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success
                      failure:(nullable void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{
    
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET"
                                                        URLString:URLString
                                                       parameters:parameters
                                                          headers:headers
                                                   uploadProgress:nil
                                                 downloadProgress:downloadProgress
                                                          success:success
                                                          failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

3. POST网络请求
   在POST网络请求中，有两种实现方式：

- (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
{
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"POST" URLString:URLString parameters:parameters headers:headers uploadProgress:uploadProgress downloadProgress:nil success:success failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

- (NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(nullable id)parameters
                       headers:(nullable NSDictionary<NSString *,NSString *> *)headers
     constructingBodyWithBlock:(nullable void (^)(id<AFMultipartFormData> _Nonnull))block
                      progress:(nullable void (^)(NSProgress * _Nonnull))uploadProgress
                       success:(nullable void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success failure:(void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{
    NSError *serializationError = nil;
    NSMutableURLRequest *request = [self.requestSerializer multipartFormRequestWithMethod:@"POST" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters constructingBodyWithBlock:block error:&amp;serializationError];
    for (NSString *headerField in headers.keyEnumerator) {
        [request setValue:headers[headerField] forHTTPHeaderField:headerField];
    }
    if (serializationError) {
        if (failure) {
            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
                failure(nil, serializationError);
            });
        }
        
        return nil;
    }
    
    __block NSURLSessionDataTask *task = [self uploadTaskWithStreamedRequest:request progress:uploadProgress completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
        if (error) {
            if (failure) {
                failure(task, error);
            }
        } else {
            if (success) {
                success(task, responseObject);
            }
        }
    }];
    
    [task resume];
    
    return task;
}

4. PUT网络请求

- (NSURLSessionDataTask *)PUT:(NSString *)URLString
                   parameters:(nullable id)parameters
                      headers:(nullable NSDictionary<NSString *,NSString *> *)headers
                      success:(nullable void (^)(NSURLSessionDataTask *task, id responseObject))success
                      failure:(nullable void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PUT" URLString:URLString parameters:parameters headers:headers uploadProgress:nil downloadProgress:nil success:success failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

5. PATCH网络请求

- (NSURLSessionDataTask *)PATCH:(NSString *)URLString
                     parameters:(nullable id)parameters
                        headers:(nullable NSDictionary<NSString *,NSString *> *)headers
                        success:(nullable void (^)(NSURLSessionDataTask *task, id responseObject))success
                        failure:(nullable void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PATCH" URLString:URLString parameters:parameters headers:headers uploadProgress:nil downloadProgress:nil success:success failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

6. DELETE网络请求

- (NSURLSessionDataTask *)DELETE:(NSString *)URLString
                      parameters:(nullable id)parameters
                         headers:(nullable NSDictionary<NSString *,NSString *> *)headers
                         success:(nullable void (^)(NSURLSessionDataTask *task, id responseObject))success
                         failure:(nullable void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"DELETE" URLString:URLString parameters:parameters headers:headers uploadProgress:nil downloadProgress:nil success:success failure:failure];
    
    [dataTask resume];
    
    return dataTask;
}

7. 自定义请求方式

- (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
{
    NSError *serializationError = nil;
    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&amp;serializationError];
    for (NSString *headerField in headers.keyEnumerator) {
        [request setValue:headers[headerField] forHTTPHeaderField:headerField];
    }
    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

简介

AFURLSessionManager负责生成对应的NSURLSession的实例，管理AFNetworkReachabilityManager和AFSecurityPolicy，以此一来查看网络的连接情况，二来保证请求的安全，同时初始化生成一个AFJSONResponseSerializer的实例来序列化HTTP的响应结果。

属性和接口

第一块：

初始化生成一个AFURLSessionManager单例对象

- (NSURLSession *)session {
    
    @synchronized (self) {
        if (!_session) {
            _session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:self.operationQueue];
        }
    }
    return _session;
}

第二块：针对不同request的请求

在上面的网络请求方法中，都调用了这个方法dataTaskWithRequest，现在看看它是怎么实现的，这里主要来看一下uploadTaskWithRequest、downloadTaskWithRequest和downloadTaskWithResumeData这三个方法：

- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request
                                         fromFile:(NSURL *)fileURL
                                         progress:(void (^)(NSProgress *uploadProgress)) uploadProgressBlock
                                completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithRequest:request fromFile:fileURL];
    
    if (uploadTask) {
        [self addDelegateForUploadTask:uploadTask
                              progress:uploadProgressBlock
                     completionHandler:completionHandler];
    }

    return uploadTask;
}

- (NSURLSessionUploadTask *)uploadTaskWithRequest:(NSURLRequest *)request
                                         fromData:(NSData *)bodyData
                                         progress:(void (^)(NSProgress *uploadProgress)) uploadProgressBlock
                                completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithRequest:request fromData:bodyData];
    
    [self addDelegateForUploadTask:uploadTask progress:uploadProgressBlock completionHandler:completionHandler];

    return uploadTask;
}
- (NSURLSessionUploadTask *)uploadTaskWithStreamedRequest:(NSURLRequest *)request
                                                 progress:(void (^)(NSProgress *uploadProgress)) uploadProgressBlock
                                        completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
    NSURLSessionUploadTask *uploadTask = [self.session uploadTaskWithStreamedRequest:request];

    [self addDelegateForUploadTask:uploadTask progress:uploadProgressBlock completionHandler:completionHandler];

    return uploadTask;
}

uploadTaskWithRequest根据不同的数据创建一个NSURLSessionUploadTask任务，最终都会走到addDelegateForUploadTask为对应的uploadTask设置代理；

//为data任务增加代理
- (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] initWithTask:dataTask];
    delegate.manager = self;
    delegate.completionHandler = completionHandler;

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

    delegate.uploadProgressBlock = uploadProgressBlock;
    delegate.downloadProgressBlock = downloadProgressBlock;
}
为upload任务添加代理
- (void)addDelegateForUploadTask:(NSURLSessionUploadTask *)uploadTask
                        progress:(void (^)(NSProgress *uploadProgress)) uploadProgressBlock
               completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler
{
 	//生成局部代理，弱持有AFURLSessionManager对象。设置其manager和completionHandler
 	//由于这里是弱持有，所以不会循环引用。
    AFURLSessionManagerTaskDelegate *delegate = [[AFURLSessionManagerTaskDelegate alloc] initWithTask:uploadTask];
    delegate.manager = self;
    delegate.completionHandler = completionHandler;
	//设置会话任务的描述
    uploadTask.taskDescription = self.taskDescriptionForSessionTasks;
	//调用setDelegate，存储datatask
    [self setDelegate:delegate forTask:uploadTask];

    delegate.uploadProgressBlock = uploadProgressBlock;
}
//为download添加代理
- (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;
}

这三个方法都是为不同的任务设置代理，最终都会调用setDelegate设置代理并存储datatask任务；

- (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];
}

这个方法主要是把代理和task建立映射关系，并且存储到事先声明好的字典当中；同时为当前task添加监听；在添加监听的方法中，taskDidResume和taskDidSuspend为接收到通知后的处理方法；用来恢复任务和暂停任务；至此，对于初始化的时候获取当前session中的所有task，已经为它们重新设置一遍代理。

- (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];
        [self removeDelegateForTask:task];
    }

    if (self.taskDidComplete) {
        self.taskDidComplete(session, task, error);
    }
}

在这里面，当一个网络请求完成时，会执行系统的代理方法，并从mutableTaskDelegatesKeyedByTaskIdentifier中移除AFURLSessionManagerTaskDelegate *delegate对象，并执行每个请求的[delegate URLSession:session task:task didCompleteWithError:error];方法。

以上是NSURLSession中的两个类的分析，AFNetWorking中的其他类的分析后续。

代码007普通

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