AFNetworking是封裝的NSURLSession的網(wǎng)絡(luò)請求，由五個模塊組成：分別由NSURLSession,Security,Reachability,Serialization,UIKit五部分組成
NSURLSession：網(wǎng)絡(luò)通信模塊（核心模塊） 對應(yīng) AFNetworking中的 AFURLSessionManager和對HTTP協(xié)議進(jìn)行特化處理的 AFHTTPSessionManager,AFHTTPSessionManager是繼承于AFURLSessionmanager的
Security：網(wǎng)絡(luò)通訊安全策略模塊 對應(yīng) AFSecurityPolicy
Reachability：網(wǎng)絡(luò)狀態(tài)監(jiān)聽模塊 對應(yīng)AFNetworkReachabilityManager
Serialization：網(wǎng)絡(luò)通信信息序列化、反序列化模塊 對應(yīng) AFURLResponseSerialization
UIKit：對于iOS UIKit的擴(kuò)展庫
創(chuàng)建
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
其內(nèi)部方法最終調(diào)用
- (instancetype)initWithBaseURL:(NSURL *)url方法來初始化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;
}
該方法同時初始化了requestSerializer和responseSerializer
之后在進(jìn)行網(wǎng)絡(luò)請求時，會調(diào)用GET或POST方法，這里用POST舉例
[manager POST:@"" parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"success");
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
NSLog(@"failure");
}];
內(nèi)部實現(xiàn)方法為：
- (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;
}
這里是使用的dataTaskWithHTTPMethod方法新建了一個NSURLSessionDataTask任務(wù)，然后執(zhí)行它。
dataTaskWithHTTPMethod方法的內(nèi)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新建一個NSMutableURLRequest
NSError *serializationError = nil;
NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
//1.2判斷是否新建成功
if (serializationError) {
if (failure) {
dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
failure(nil, serializationError);
});
}
return nil;
}
//2.1新建NSURLSessionDataTask
//這個dataTask需要回調(diào)給外部,所以需要__block修飾
__block NSURLSessionDataTask *dataTask = nil;
dataTask = [self dataTaskWithRequest:request
uploadProgress:uploadProgress
downloadProgress:downloadProgress
completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
//2.2設(shè)置回調(diào)
if (error) {
if (failure) {
failure(dataTask, error);
}
} else {
if (success) {
success(dataTask, responseObject);
}
}
}];
return dataTask;
}
這里可以分兩部分看，第一部分是創(chuàng)建一個NSMutableURLRequest，創(chuàng)建成功進(jìn)行下一步，創(chuàng)建失敗則回調(diào)failure(nil, serializationError);方法，創(chuàng)建NSMutableURLRequest：
- (NSMutableURLRequest *)requestWithMethod:(NSString *)method
URLString:(NSString *)URLString
parameters:(id)parameters
error:(NSError *__autoreleasing *)error
{
//檢驗參數(shù)的完整性
NSParameterAssert(method);
NSParameterAssert(URLString);
NSURL *url = [NSURL URLWithString:URLString];
NSParameterAssert(url);
//新建一個NSMutableURLRequest，設(shè)置起請求類型
NSMutableURLRequest *mutableRequest = [[NSMutableURLRequest alloc] initWithURL:url];
mutableRequest.HTTPMethod = method;
//循環(huán)遍歷給mutableRequest設(shè)置參數(shù)
for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
if ([self.mutableObservedChangedKeyPaths containsObject:keyPath]) {
[mutableRequest setValue:[self valueForKeyPath:keyPath] forKey:keyPath];
}
}
//將傳入的parameters進(jìn)行編碼，并添加到request中
//不同的請求格式內(nèi)部調(diào)用方法不一樣（AFHTTPRequestSerializer，AFJSONRequestSerializer，AFPropertyListRequestSerializer）
mutableRequest = [[self requestBySerializingRequest:mutableRequest withParameters:parameters error:error] mutableCopy];
return mutableRequest;
}
當(dāng)NSMutableURLRequest創(chuàng)建成功時，進(jìn)入第二步，新建一個NSURLSessionDataTask，設(shè)置failure和success的回調(diào)函數(shù)，然后返回新建的NSURLSessionDataTask，新建NSURLSessionDataTask的方法內(nèi)部實現(xiàn)：
- (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)這個函數(shù)。這個函數(shù)主要的目的是為了解決iOS8之前的一個bug
新建一個NSURLSessionDataTask，在url_session_manager_create_task_safely中初始化，然后用addDelegateForDataTask方法添加代理，最后返回該dataTask，添加代理的具體內(nèi)部實現(xiàn)：
- (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;
}
