AFNetworking作為iOS開發(fā)中最常用的網絡請求框架之一驾孔,其內部實現究竟是怎么一步一步實現的呢?現在我們來大致分析下其內部源碼,由于本人水平有限,說錯了的地方請大家積極指正华坦,謝謝!
以3.0.0的版本為例,其源碼結構如下:
1.NSURLSession文件夾中的類專門用于網絡通信,其中最核心的類是AFURLSessionManager,其中的AFHTTPSessionManager這個類是前者的子類歹袁,顧名思義,AFHTTPSessionManager這個類是專門用于Http請求,
2.Reachability中的AFNetworkRechabilityManager專門用于檢測網絡變化
3.Security用于網絡安全策略
4.Serilization中的兩個類專門用于請求頭、響應頭的處理
其類與類之間的關系如下圖所示:
可以看到AFSessionManager中實現的最核心的類是Apple提供的系統(tǒng)類NSURLSession和NSURLSessionDataTask,這兩個類提供了網絡請求所需要的全部,由于我們最常使用的類是AFHTTPSessionManager,在進行網絡請求時捷沸,我們一般使用一個AFHTTPSessionManager的實例變量來進行請求,如下代碼所示:
AFHTTPSessionManager *httpClient = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:@"www.baidu.com"]];
httpClient.requestSerializer = [AFHTTPRequestSerializer serializer];
httpClient.responseSerializer = [AFHTTPResponseSerializer serializer];
[httpClient POST:@""
parameters:@{}
success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
//獲取responseObject的數據,在主線程做UI刷新操作
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
}];
首先設置基地址:
- (instancetype)initWithBaseURL:(NSURL *)url
sessionConfiguration:(NSURLSessionConfiguration *)configuration
{
self = [super initWithSessionConfiguration:configuration];
if (!self) {
return nil;
}
//http://www.baidu.com 確保完整路徑的基地址
// 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;
//請求和響應序列化工具
self.requestSerializer = [AFHTTPRequestSerializer serializer];
self.responseSerializer = [AFJSONResponseSerializer serializer];
return self;
}
這里設置了一個requestSerializer和responseSerializer,這兩個類的作用是設置請求頭序仙、響應頭相關的信息,主要用于傳輸不同類型的文件并設置不同的contentType等等,我們進入requestSerializer看下源碼看具體做了什么:
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
//編碼
self.stringEncoding = NSUTF8StringEncoding;
//設置請求頭
self.mutableHTTPRequestHeaders = [NSMutableDictionary dictionary];
// Accept-Language HTTP Header; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.4
NSMutableArray *acceptLanguagesComponents = [NSMutableArray array];
[[NSLocale preferredLanguages] enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
float q = 1.0f - (idx * 0.1f);
[acceptLanguagesComponents addObject:[NSString stringWithFormat:@"%@;q=%0.1g", obj, q]];
*stop = q <= 0.5f;
}];
//服務器接收語言
[self setValue:[acceptLanguagesComponents componentsJoinedByString:@", "] forHTTPHeaderField:@"Accept-Language"];
//用戶代理
NSString *userAgent = nil;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
#if TARGET_OS_IOS
//獲取請求設備的相關信息 用戶代理
// User-Agent Header; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.43
userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
#elif TARGET_OS_WATCH
// User-Agent Header; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.43
userAgent = [NSString stringWithFormat:@"%@/%@ (%@; watchOS %@; Scale/%0.2f)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[WKInterfaceDevice currentDevice] model], [[WKInterfaceDevice currentDevice] systemVersion], [[WKInterfaceDevice currentDevice] screenScale]];
#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED)
userAgent = [NSString stringWithFormat:@"%@/%@ (Mac OS X %@)", [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleExecutableKey] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleIdentifierKey], [[NSBundle mainBundle] infoDictionary][@"CFBundleShortVersionString"] ?: [[NSBundle mainBundle] infoDictionary][(__bridge NSString *)kCFBundleVersionKey], [[NSProcessInfo processInfo] operatingSystemVersionString]];
#endif
#pragma clang diagnostic pop
if (userAgent) {
if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
NSMutableString *mutableUserAgent = [userAgent mutableCopy];
if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
userAgent = mutableUserAgent;
}
}
[self setValue:userAgent forHTTPHeaderField:@"User-Agent"];
}
// HTTP Method Definitions; see http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html
self.HTTPMethodsEncodingParametersInURI = [NSSet setWithObjects:@"GET", @"HEAD", @"DELETE", nil];
self.mutableObservedChangedKeyPaths = [NSMutableSet set];
for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
if ([self respondsToSelector:NSSelectorFromString(keyPath)]) {
[self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:AFHTTPRequestSerializerObserverContext];
}
}
return self;
}
這些信息主要是和后臺人員溝通確定的粱锐,比如一般的后臺請求蔬崩,我們要設置AcceptableContentType為applicaiont/json跨琳,注明接受類型是已經被后臺人員轉好的json湾宙,在回調中我們就可以直接獲取到json數據死宣,而不用去進行轉換, 有的時候博秫,我們在勤奮求的時候巴碗,報錯"Request failed: unacceptable content-type",就需要在請求頭的contentype列表里面添加一些指定的contentType.
其次就是主體的請求代碼:
[httpClient POST:@""
parameters:@{}
success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
//獲取responseObject的數據,在主線程做UI刷新操作
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
}];
我們點進去看看,可以看到所有的請求方法都是基于下面這個方法來構建的:
/**
構建網絡請求:所有請求(POST、GET、DELETE趋艘、PATCH、HEAD)都基于這個方法來構建起來的
@param method POST、GET矛绘、DELETE斯够、PATCH抓督、HEAD
@param URLString 請求地址
@param parameters 請求參數
@param uploadProgress 上傳進度回調
@param downloadProgress 下載進度列表
@param success 成功回調
@param failure 失敗回調
@return NSURLSessionDataTask網絡請求
*/
- (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
我們重點來分析下這個方法里面的代碼:
// 根據請求地址、方法阳液、參數構建網絡請求NSMutableURLRequest
NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
這里使用了requestSerializer 的私有方法 method揣炕、params來構建了一個NSMutableURLRequest,并設置了請求體畸陡,請求頭信息等等:代碼如下:
- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
withParameters:(id)parameters
error:(NSError *__autoreleasing *)error
{
NSParameterAssert(request);
NSMutableURLRequest *mutableRequest = [request mutableCopy];
///設置請求頭信息
[self.HTTPRequestHeaders enumerateKeysAndObjectsUsingBlock:^(id field, id value, BOOL * __unused stop) {
if (![request valueForHTTPHeaderField:field]) {
[mutableRequest setValue:value forHTTPHeaderField:field];
}
}];
NSString *query = nil;
if (parameters) {
if (self.queryStringSerialization) {
NSError *serializationError;
query = self.queryStringSerialization(request, parameters, &serializationError);
if (serializationError) {
if (error) {
*error = serializationError;
}
return nil;
}
} else {
switch (self.queryStringSerializationStyle) {
case AFHTTPRequestQueryStringDefaultStyle:
query = AFQueryStringFromParameters(parameters);
break;
}
}
}
//判斷是否是GET/HEAD/DELETE方法罩锐, 對于GET/HEAD/DELETE方法涩惑,把參數加到URL后面,這也就是GET請求里面的參數會暴露在請求地址里面
if ([self.HTTPMethodsEncodingParametersInURI containsObject:[[request HTTPMethod] uppercaseString]]) {
if (query) {
mutableRequest.URL = [NSURL URLWithString:[[mutableRequest.URL absoluteString] stringByAppendingFormat:mutableRequest.URL.query ? @"&%@" : @"?%@", query]];
}
} else {
// #2864: an empty string is a valid x-www-form-urlencoded payload
//一般用于POST請求
if (!query) {
query = @"";
}
///設置Content-Type HTTP頭桑驱,告訴服務端body的參數編碼類型
if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
[mutableRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
}
//設置請求體信息 將json字符串轉化為NSData類型
[mutableRequest setHTTPBody:[query dataUsingEncoding:self.stringEncoding]];
}
return mutableRequest;
}
接下來的就是構架一個NSURLSessionDataTask:
__block NSURLSessionDataTask *dataTask = nil;
dataTask = [self dataTaskWithRequest:request
uploadProgress:uploadProgress
downloadProgress:downloadProgress
completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
//成功失敗回調
if (error) {
if (failure) {
failure(dataTask, error);
}
} else {
if (success) {
success(dataTask, responseObject);
}
}
}]; //使用這個方法構建的task 需要手動resume 才會啟動任務
///使用NSURLSession和NSURLSessionDataTask請求數據
- (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(^{
//這里使用了NSURLSession來實例化一個dataTask
dataTask = [self.session dataTaskWithRequest:request];
});
//為task添加代理來傳輸數據等相關信息
[self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler];
return dataTask;
}
///給NSURLSessionDataTask對象實例設置Delegate痊硕。用于實時了解網絡請求
- (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] init];
delegate.manager = self;
delegate.completionHandler = completionHandler;
dataTask.taskDescription = self.taskDescriptionForSessionTasks;
//為dataTask設置代理來接受并處理數據
[self setDelegate:delegate forTask:dataTask];
delegate.uploadProgressBlock = uploadProgressBlock;
delegate.downloadProgressBlock = downloadProgressBlock;
}
- (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate
forTask:(NSURLSessionTask *)task
{
NSParameterAssert(task);
NSParameterAssert(delegate);
//加鎖 避免同時修改數據,造成線程安全問題
[self.lock lock];
self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
[delegate setupProgressForTask:task];
[self addNotificationObserverForTask:task];
[self.lock unlock];
}
///這里使用KVO監(jiān)測task的請求過程
- (void)setupProgressForTask:(NSURLSessionTask *)task {
__weak __typeof__(task) weakTask = task;
self.uploadProgress.totalUnitCount = task.countOfBytesExpectedToSend;
self.downloadProgress.totalUnitCount = task.countOfBytesExpectedToReceive;
[self.uploadProgress setCancellable:YES];
[self.uploadProgress setCancellationHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask cancel];
}];
[self.uploadProgress setPausable:YES];
[self.uploadProgress setPausingHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask suspend];
}];
if ([self.uploadProgress respondsToSelector:@selector(setResumingHandler:)]) {
[self.uploadProgress setResumingHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask resume];
}];
}
[self.downloadProgress setCancellable:YES];
[self.downloadProgress setCancellationHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask cancel];
}];
[self.downloadProgress setPausable:YES];
[self.downloadProgress setPausingHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask suspend];
}];
if ([self.downloadProgress respondsToSelector:@selector(setResumingHandler:)]) {
[self.downloadProgress setResumingHandler:^{
__typeof__(weakTask) strongTask = weakTask;
[strongTask resume];
}];
}
[task addObserver:self
forKeyPath:NSStringFromSelector(@selector(countOfBytesReceived))
options:NSKeyValueObservingOptionNew
context:NULL];
[task addObserver:self
forKeyPath:NSStringFromSelector(@selector(countOfBytesExpectedToReceive))
options:NSKeyValueObservingOptionNew
context:NULL];
[task addObserver:self
forKeyPath:NSStringFromSelector(@selector(countOfBytesSent))
options:NSKeyValueObservingOptionNew
context:NULL];
[task addObserver:self
forKeyPath:NSStringFromSelector(@selector(countOfBytesExpectedToSend))
options:NSKeyValueObservingOptionNew
context:NULL];
[self.downloadProgress addObserver:self
forKeyPath:NSStringFromSelector(@selector(fractionCompleted))
options:NSKeyValueObservingOptionNew
context:NULL];
[self.uploadProgress addObserver:self
forKeyPath:NSStringFromSelector(@selector(fractionCompleted))
options:NSKeyValueObservingOptionNew
context:NULL];
}
//監(jiān)聽下載和上傳任務的數據并回調
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {
if ([object isKindOfClass:[NSURLSessionTask class]]) {
if ([keyPath isEqualToString:NSStringFromSelector(@selector(countOfBytesReceived))]) {
self.downloadProgress.completedUnitCount = [change[@"new"] longLongValue];
} else if ([keyPath isEqualToString:NSStringFromSelector(@selector(countOfBytesExpectedToReceive))]) {
self.downloadProgress.totalUnitCount = [change[@"new"] longLongValue];
} else if ([keyPath isEqualToString:NSStringFromSelector(@selector(countOfBytesSent))]) {
self.uploadProgress.completedUnitCount = [change[@"new"] longLongValue];
} else if ([keyPath isEqualToString:NSStringFromSelector(@selector(countOfBytesExpectedToSend))]) {
self.uploadProgress.totalUnitCount = [change[@"new"] longLongValue];
}
}
else if ([object isEqual:self.downloadProgress]) {
//下載回調
if (self.downloadProgressBlock) {
self.downloadProgressBlock(object);
}
}
else if ([object isEqual:self.uploadProgress]) {
if (self.uploadProgressBlock) {
//上傳回調
self.uploadProgressBlock(object);
}
}
}
- (void)URLSession:(NSURLSession *)session
dataTask:(NSURLSessionDataTask *)dataTask
didReceiveData:(NSData *)data {
//獲取NSURLSessionDataTask代理對象
AFURLSessionManagerTaskDelegate *delegate = [self delegateForTask:dataTask];
//試用delegate追加數據
[delegate URLSession:session dataTask:dataTask didReceiveData:data];
//數據接受回調
if (self.dataTaskDidReceiveData) {
self.dataTaskDidReceiveData(session, dataTask, data);
}
}
//接收數據
- (void)URLSession:(__unused NSURLSession *)session
dataTask:(__unused NSURLSessionDataTask *)dataTask
didReceiveData:(NSData *)data
{
[self.mutableData appendData:data];
}
@interface AFURLSessionManagerTaskDelegate : NSObject <NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>
AFURLSessionManagerTaskDelegate接管了NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate的各種回調刚盈,然后做內部數據處理挂脑,崭闲。這也是第三方網絡請求框架的重點,讓網絡請求更加易用牺蹄,好用薄翅。
當然氓奈,由于本人技術有限舀奶,很多東西沒理解透徹斋射,如果有錯誤之處,歡迎大家指正涧至,共同進步,后續(xù)的深入理解會繼續(xù)寫文章大家一起談論,如果親覺著這篇文章對于理解AFN有幫助的話桑包,請下方點贊,謝謝!
-------作者:mrChan1234