一、概述
从上图可以发现,AFNetworking框架的结构比较清晰简洁,主要范围5个部分:
- 网络通信模块:URLSession
- 网络状态监听模块:Reachability
- 网络通信安全模块:Security
- 网络通信序列化模块:Serialization
- 对UIKit框架扩展部分:UIKit(以Catagory形式添加特性)
AFNetworking的核心是AFURLSessionManager类,这个类基于NSURLSession,围绕NSURLSession做了一系列的封装,其余的四个类都是该类用于网络通信的一个属性或对已有UIKit的一个扩展工具包。
其中AFHTTPSessionManager类是继承于AFURLSessionManager的,我们使用AFNetworking时,都是用AFHTTPSessionManager,但它本身没有做实事的,只是做了一些简单的封装,把请求逻辑分发给父类AFURLSessionManager。
二、AFNetworking使用
例子:
AFHTTPSessionManager *session = [AFHTTPSessionManager manager];
session.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/html",@"application/json", @"text/json" ,@"text/javascript", nil];
session.responseSerializer = [AFHTTPResponseSerializer serializer];
[session GET:@"https://www.baidu.com"
parameters:nil
headers:nil
progress:nil
success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"请求成功");
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
NSLog(@"请求失败");
}];
三、AFNetworking使用的代码分析
3.1 [AFHTTPSessionManager manager]
AFHTTPSessionManager manage的实现
+ (instancetype)manager {
return [[[self class] alloc] initWithBaseURL:nil];
}
- (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;
}
if ([[url path] length] > 0 && ![[url absoluteString] hasSuffix:@"/"]) {
url = [url URLByAppendingPathComponent:@""];
}
self.baseURL = url;
self.requestSerializer = [AFHTTPRequestSerializer serializer];
self.responseSerializer = [AFJSONResponseSerializer serializer];
return self;
}
进入到AFURLSessionManager的- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration方法中分析
- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration {
self = [super init];
if (!self) {
return nil;
}
if (!configuration) {
configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
}
// 1. 设置全局的网络行为策略的配置
self.sessionConfiguration = configuration;
// 2. 设置请求的队列,默认最大的并发数为1
self.operationQueue = [[NSOperationQueue alloc] init];
// (1)这里的并发数指的是回调代理的线程并发数,而不是请求网络的线程并发数。请求网络是由NSURLSession来做的,它内部维护了一个线程池用来做网络请求。NSURLSession调度线程是基于底层的CFSocket去发送请求和接收数据,这些线程是并发的。
// (2)AF2.x所有回调是在一条线程,这条线程是AF的常驻线程,而这一条线程正式AF调度request的思想精髓所在。所以线程数设置为1的第一个目的是和之前版本保持一致;
// (3)因为跟代理相关的一些操作AF都使用了NSLock,所以Queue的并发数设置为n,也会因为多线程回调、锁的等待,导致提升的程序速度并不明显,反而多task回调导致的多线程并发,平白浪费了部分性能。至少回调的事件,是不需要多线程并发的,回调没有了NSLock的等待事件,所以对事件并没有多大影响。
self.operationQueue.maxConcurrentOperationCount = 1;
// 3. 设置网络请求响应的数据解析实例
self.responseSerializer = [AFJSONResponseSerializer serializer];
// 4. 设置网络请求安全策略实例(后续说明该实例)
self.securityPolicy = [AFSecurityPolicy defaultPolicy];
// 5. 初始化全局的网络状态监听的实例
#if !TARGET_OS_WATCH
self.reachabilityManager = [AFNetworkReachabilityManager sharedManager];
#endif
// 6. 将taskID与其Delegate绑定,实现解耦(后续进行分析)
self.mutableTaskDelegatesKeyedByTaskIdentifier = [[NSMutableDictionary alloc] init];
self.lock = [[NSLock alloc] init];
self.lock.name = AFURLSessionManagerLockName;
// 7. self.session采用懒加载,根据configuration,operationQueue初始化全局的NSURLSession
[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;
}
- (NSURLSession *)session {
@synchronized (self) {
if (!_session) {
_session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:self.operationQueue];
}
}
return _session;
}
3.2 NSURLSessionConfiguration 全局的网络行为策略的配置
简单罗列以下两点:
1.NSURLSessionConfiguration可以控制网络请求中的缓存策略,超时设置等;
2.如果需要改变网络请求的行为策略,必须重新在更改NSURLSessionConfiguration后再创建一个新的NSURLSession。
3.3 AFHTTPSessionManager GET: parameters: headers: progress: success: failure: 方法
3.3.1 NSURLSessionTask
这里引入了一个新的类:NSURLSessionDataTask。NSURLSessionDataTask继承了NSURLSessionTask。** NSURLSessionTask**的官方说明:
简单罗列以下两点:
1.NSURLSessionTask是官方提供的几种网络任务类的基类;
2.官方提供了三种任务处理的子类:简单数据处理任务类、上传任务类和下载任务类。
3.3.2 AFHTTPSessionManager dataTaskWithHTTPMethod:...方法实现与分析
- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
URLString:(NSString *)URLString
parameters:(id)parameters
headers:(NSDictionary<NSString *,NSString *> *)headers
uploadProgress:(void (^)(NSProgress * _Nonnull))uploadProgress
downloadProgress:(void (^)(NSProgress * _Nonnull))downloadProgress
success:(void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success
failure:(void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure {
NSError *serializationError = nil;
// 1.通过全局配置的requestSerializer初始化一个请求的实例
NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
for (NSString *headerField in headers.keyEnumerator) {
[request setValue:headers[headerField] forKey:headerField];
}
if (serializationError) {
if (failure) {
dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
failure(nil, serializationError);
});
}
return nil;
}
// 2.根据请求的实例再初始化一个task的实例
__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;
}
3.3.3 [AFURLSessionManager addDelegateForDataTask:...]方法,用于task与delegate的绑定
// 1. 根据请求信息初始化一个task实例
- (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 {
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:request];
[self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler];
return dataTask;
}
- (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
{
// 2.初始化一个任务的代理
AFURLSessionManagerTaskDelegate *delegate = [[AFURLSessionManagerTaskDelegate alloc] initWithTask:dataTask];
delegate.manager = self;
// 此处赋值了请求完成的回调,后续会用到
delegate.completionHandler = completionHandler;
// 3.利用全局的字典存储绑定信息,key为taskID,value为代理的实例。
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];
// 1.绑定taskID与代理self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
// 2.使用KVO对一些方法监听,返回上传或下载的进度
self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
[self addNotificationObserverForTask:task];
[self.lock unlock];
}
3.3.4 NSURLSessionTaskDelegate协议中的URLSession:task:didCompleteWithError:方法
NSURLSessionTaskDelegate协议包含NSURLSessionDelegate协议
当请求收到了响应后,会触发- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(nullable NSError *)error;回调(AFURLSessionManager的session属性懒加载时,设置了delegate为self,会触发该代理的方法),以下是方法中的具体处理。
// AFURLSessionManager.m中NSURLSessionTaskDelegate方法的实现,该方法由系统自动触发
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
// 1.根据task获取绑定的代理实例
AFURLSessionManagerTaskDelegate *delegate = [self delegateForTask:task];
// delegate may be nil when completing a task in the background
if (delegate) {
// 2.统一处理,调用AFURLSessionManagerTaskDelegate的同名方法。
[delegate URLSession:session task:task didCompleteWithError:error];
[self removeDelegateForTask:task];
}
if (self.taskDidComplete) {
self.taskDidComplete(session, task, error);
}
}
// AFURLSessionManagerTaskDelegate.m中NSURLSessionTaskDelegate方法的实现,该方法在AFURLSessionManager中通过delegate调用。
- (void)URLSession:(__unused NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
error = objc_getAssociatedObject(task, AuthenticationChallengeErrorKey) ?: error;
__strong AFURLSessionManager *manager = self.manager;
__block id responseObject = nil;
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 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) {
// 1.iOS网络框架返回的错误信息处理
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 {
// 2.请求成功后需要用响应的数据解析类的responseSerializer实例处理返回的数据
// 数据通过NSURLSessionDataDelegate协议的- (void)URLSession:(__unused NSURLSession *)session dataTask:(__unused NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data方法返回
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(), ^{
// 3.绑定task与处理的数据代理时,传入代理的完成的回调
if (self.completionHandler) {
self.completionHandler(task.response, responseObject, serializationError);
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
});
});
});
}
}
参考来源:
https://toutiao.io/posts/dibcw7/preview
https://www.cnblogs.com/ederwin/articles/10592839.html