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AFNetworking 底层分析

AFNetworking 底层分析

作者: Foxhoundsun | 来源:发表于2020-04-28 02:38 被阅读0次

AFNetworking是封装的NSURLSession的网络请求,由五个模块组成:分别由NSURLSession,Security,Reachability,Serialization,UIKit五部分组成

NSURLSession:网络通信模块(核心模块) 对应 AFNetworking中的 AFURLSessionManager和对HTTP协议进行特化处理的 AFHTTPSessionManager,AFHTTPSessionManager是继承于AFURLSessionmanager的

Security:网络通讯安全策略模块 对应 AFSecurityPolicy

Reachability:网络状态监听模块 对应AFNetworkReachabilityManager

Serialization:网络通信信息序列化、反序列化模块 对应 AFURLResponseSerialization

UIKit:对于iOS UIKit的扩展库

创建

AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];

其内部方法最终调用
- (instancetype)initWithBaseURL:(NSURL *)url方法来初始化AFHTTPSessionManager


- (instancetype)initWithBaseURL:(NSURL *)url

 sessionConfiguration:(NSURLSessionConfiguration *)configuration

{

 self = [super initWithSessionConfiguration:configuration];

 if (!self) {

 return nil;

 }

 // Ensure terminal slash for baseURL path, so that NSURL +URLWithString:relativeToURL: works as expected

 if ([[url path] length] > 0 && ![[url absoluteString] hasSuffix:@"/"]) {

 url = [url URLByAppendingPathComponent:@""];

 }

 self.baseURL = url;

 //初始化

 self.requestSerializer = [AFHTTPRequestSerializer serializer];

 self.responseSerializer = [AFJSONResponseSerializer serializer];

 return self;

}

该方法同时初始化了requestSerializerresponseSerializer

之后在进行网络请求时,会调用GETPOST方法,这里用POST举例


[manager POST:@"" parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {

 NSLog(@"success");

 } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {

 NSLog(@"failure");

 }];

内部实现方法为:


- (NSURLSessionDataTask *)POST:(NSString *)URLString

 parameters:(id)parameters

 progress:(void (^)(NSProgress * _Nonnull))uploadProgress

 success:(void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success

 failure:(void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure

{

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

 [dataTask resume];

 return dataTask;

}

这里是使用的dataTaskWithHTTPMethod方法新建了一个NSURLSessionDataTask任务,然后执行它。

dataTaskWithHTTPMethod方法的内部原理:


- (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

{

 //1.1新建一个NSMutableURLRequest

 NSError *serializationError = nil;

 NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];

 //1.2判断是否新建成功

 if (serializationError) {

 if (failure) {

 dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{

 failure(nil, serializationError);

 });

 }

 return nil;

 }

 //2.1新建NSURLSessionDataTask

 //这个dataTask需要回调给外部,所以需要__block修饰

 __block NSURLSessionDataTask *dataTask = nil;

 dataTask = [self dataTaskWithRequest:request

 uploadProgress:uploadProgress

 downloadProgress:downloadProgress

 completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {

 //2.2设置回调

 if (error) {

 if (failure) {

 failure(dataTask, error);

 }

 } else {

 if (success) {

 success(dataTask, responseObject);

 }

 }

 }];

 return dataTask;

}

这里可以分两部分看,第一部分是创建一个NSMutableURLRequest,创建成功进行下一步,创建失败则回调failure(nil, serializationError);方法,创建NSMutableURLRequest


- (NSMutableURLRequest *)requestWithMethod:(NSString *)method

 URLString:(NSString *)URLString

 parameters:(id)parameters

 error:(NSError *__autoreleasing *)error

{

 //检验参数的完整性

 NSParameterAssert(method);

 NSParameterAssert(URLString);

 NSURL *url = [NSURL URLWithString:URLString];

 NSParameterAssert(url);

 //新建一个NSMutableURLRequest,设置起请求类型

 NSMutableURLRequest *mutableRequest = [[NSMutableURLRequest alloc] initWithURL:url];

 mutableRequest.HTTPMethod = method;

 //循环遍历给mutableRequest设置参数

 for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {

 if ([self.mutableObservedChangedKeyPaths containsObject:keyPath]) {

 [mutableRequest setValue:[self valueForKeyPath:keyPath] forKey:keyPath];

 }

 }

 //将传入的parameters进行编码,并添加到request中

 //不同的请求格式内部调用方法不一样(AFHTTPRequestSerializer,AFJSONRequestSerializer,AFPropertyListRequestSerializer)

 mutableRequest = [[self requestBySerializingRequest:mutableRequest withParameters:parameters error:error] mutableCopy];

return mutableRequest;

}

NSMutableURLRequest创建成功时,进入第二步,新建一个NSURLSessionDataTask,设置failuresuccess的回调函数,然后返回新建的NSURLSessionDataTask,新建NSURLSessionDataTask的方法内部实现:


- (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;

}

使用了url_session_manager_create_task_safely(dispatch_block_t block)这个函数。这个函数主要的目的是为了解决iOS8之前的一个bug

新建一个NSURLSessionDataTask,在url_session_manager_create_task_safely中初始化,然后用addDelegateForDataTask方法添加代理,最后返回该dataTask,添加代理的具体内部实现:


- (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;

}

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