AFNetworking 最新版本是3.1.0，相对于2.x版本，删除了基于NSURLConnection的AFURLConnnectionOperation的API支持，整个网络请求的代码完全基于NSURLSession.剩余架构和2.X版本基本一样，由网络请求管理(AFURLSessionManager)，安全协议(AFSecurityPolicy)，网络状态管理(AFNetworkReachabilityManager)和序列化(AFHTTPRequestSerializer和AFHTTPResponseSerializer)组成.
AFNetworking.png
AFURLSessionManager
AFURLSessionManager定义如下:
@interface AFURLSessionManager : NSObject <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate, NSSecureCoding, NSCopying>
实现部分的url_session_manager_create_task_safely的函数解决iOS8下使用同步队列会出现问题:
static void url_session_manager_create_task_safely(dispatch_block_t block) {
if (NSFoundationVersionNumber < NSFoundationVersionNumber_With_Fixed_5871104061079552_bug) {
// Fix of bug
// Open Radar:http://openradar.appspot.com/radar?id=5871104061079552 (status: Fixed in iOS8)
// Issue about:https://github.com/AFNetworking/AFNetworking/issues/2093
dispatch_sync(url_session_manager_creation_queue(), block);
} else {
block();
}
}
交换xNSURLSessionTask的resume和suspend方法的辅助函数:
static inline void af_swizzleSelector(Class theClass, SEL originalSelector, SEL swizzledSelector) {
Method originalMethod = class_getInstanceMethod(theClass, originalSelector);
Method swizzledMethod = class_getInstanceMethod(theClass, swizzledSelector);
method_exchangeImplementations(originalMethod, swizzledMethod);
}
static inline BOOL af_addMethod(Class theClass, SEL selector, Method method) {
return class_addMethod(theClass, selector, method_getImplementation(method), method_getTypeEncoding(method));
}
AFURLSessionManger实现了NSURLSessionTaskDelegate, NSURLSessionDataDelegate和 NSURLSessionDownloadDelegate是三个协议，但是内部继续封装了AFURLSessionManagerTaskDelegate.设置Delegate的过程.
NSParameterAssert(task);
AFURLSessionManagerTaskDelegate *delegate = nil;
[self.lock lock];
delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)];
[self.lock unlock];
return delegate;
}
- (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate
forTask:(NSURLSessionTask *)task
{
NSParameterAssert(task);
NSParameterAssert(delegate);
[self.lock lock];
self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
[delegate setupProgressForTask:task];
[self addNotificationObserverForTask:task];
[self.lock unlock];
}
- (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;
[self setDelegate:delegate forTask:dataTask];
delegate.uploadProgressBlock = uploadProgressBlock;
delegate.downloadProgressBlock = downloadProgressBlock;
}
需要注意的AFURLSessionManagerTaskDelegate的修饰符是weak:
@interface AFURLSessionManagerTaskDelegate : NSObject <NSURLSessionTaskDelegate, NSURLSessionDataDelegate, NSURLSessionDownloadDelegate>
@property (nonatomic, weak) AFURLSessionManager *manager;
AFHTTPSessionManager
AFHTTPSessionManager 是AFURLSessionManger的子类，提供了GET，HEAD，POST，PUT，PATCH和DELETE六个调用的方法，GET调用如下:
- (NSURLSessionDataTask *)GET:(NSString *)URLString
parameters:(id)parameters
progress:(void (^)(NSProgress * _Nonnull))downloadProgress
success:(void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success
failure:(void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{
NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET"
URLString:URLString
parameters:parameters
uploadProgress:nil
downloadProgress:downloadProgress
success:success
failure:failure];
[dataTask resume];
return dataTask;
}
AFNetworkReachabilityManager
AFNetworkReachabilityManager中监控网络的四种状态，枚举如下:
typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
AFNetworkReachabilityStatusUnknown = -1,
AFNetworkReachabilityStatusNotReachable = 0,
AFNetworkReachabilityStatusReachableViaWWAN = 1,
AFNetworkReachabilityStatusReachableViaWiFi = 2,
};
核心实现代码:
- (void)startMonitoring {
[self stopMonitoring];
if (!self.networkReachability) {
return;
}
__weak __typeof(self)weakSelf = self;
AFNetworkReachabilityStatusBlock callback = ^(AFNetworkReachabilityStatus status) {
__strong __typeof(weakSelf)strongSelf = weakSelf;
strongSelf.networkReachabilityStatus = status;
if (strongSelf.networkReachabilityStatusBlock) {
strongSelf.networkReachabilityStatusBlock(status);
}
};
SCNetworkReachabilityContext context = {0, (__bridge void *)callback, AFNetworkReachabilityRetainCallback, AFNetworkReachabilityReleaseCallback, NULL};
SCNetworkReachabilitySetCallback(self.networkReachability, AFNetworkReachabilityCallback, &context);
SCNetworkReachabilityScheduleWithRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0),^{
SCNetworkReachabilityFlags flags;
if (SCNetworkReachabilityGetFlags(self.networkReachability, &flags)) {
AFPostReachabilityStatusChange(flags, callback);
}
});
}
AFSecurityPolicy
AFSecurityPolicy 主要作用就是验证 HTTPS 请求的证书是否有效，如果应用中有一些敏感信息或者涉及交易信息，一定要使用 HTTPS 来保证交易或者用户信息的安全.验证服务器是否被信任有三种方式:
typedef NS_ENUM(NSUInteger, AFSSLPinningMode) {
AFSSLPinningModeNone,
AFSSLPinningModePublicKey,
AFSSLPinningModeCertificate,
};
AFSSLPinningModeNone:从客户端信任的CA列表中验证证书是否有效.
AFSSLPinningModePublicKey:客户端保存服务端证书的拷贝，验证服务端证书的公钥是否一致;
AFSSLPinningModeCertificate:客户端保存服务端证书的拷贝，首先验证域名/有效期信息，然后验证两个证书是否一致.
实现过程比较简单，主要是验证证书是否受信任需要一些C语言基础:
static NSArray * AFPublicKeyTrustChainForServerTrust(SecTrustRef serverTrust) {
SecPolicyRef policy = SecPolicyCreateBasicX509();
CFIndex certificateCount = SecTrustGetCertificateCount(serverTrust);
NSMutableArray *trustChain = [NSMutableArray arrayWithCapacity:(NSUInteger)certificateCount];
for (CFIndex i = 0; i < certificateCount; i++) {
SecCertificateRef certificate = SecTrustGetCertificateAtIndex(serverTrust, i);
SecCertificateRef someCertificates[] = {certificate};
CFArrayRef certificates = CFArrayCreate(NULL, (const void **)someCertificates, 1, NULL);
SecTrustRef trust;
__Require_noErr_Quiet(SecTrustCreateWithCertificates(certificates, policy, &trust), _out);
SecTrustResultType result;
__Require_noErr_Quiet(SecTrustEvaluate(trust, &result), _out);
[trustChain addObject:(__bridge_transfer id)SecTrustCopyPublicKey(trust)];
_out:
if (trust) {
CFRelease(trust);
}
if (certificates) {
CFRelease(certificates);
}
continue;
}
CFRelease(policy);
return [NSArray arrayWithArray:trustChain];
}
AFHTTPRequestSerializer
AFHTTPRequestSerializer是最核心的地方，实现部分开头的代码展现了作者扎实的计算机基础，对URI中的非法字符进行百分比编码.
<pre><code>`NSString * AFPercentEscapedStringFromString(NSString string) {
static NSString * const kAFCharactersGeneralDelimitersToEncode = @":#[]@"; // does not include "?" or "/" due to RFC 3986 - Section 3.4
static NSString * const kAFCharactersSubDelimitersToEncode = @"!$&'()+,;=";
NSMutableCharacterSet * allowedCharacterSet = [[NSCharacterSet URLQueryAllowedCharacterSet] mutableCopy];
[allowedCharacterSet removeCharactersInString:[kAFCharactersGeneralDelimitersToEncode stringByAppendingString:kAFCharactersSubDelimitersToEncode]];
// FIXME: https://github.com/AFNetworking/AFNetworking/pull/3028
// return [string stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet];
static NSUInteger const batchSize = 50;
NSUInteger index = 0;
NSMutableString *escaped = @"".mutableCopy;
while (index < string.length) {
pragma GCC diagnostic push
pragma GCC diagnostic ignored "-Wgnu"
NSUInteger length = MIN(string.length - index, batchSize);
pragma GCC diagnostic pop
NSRange range = NSMakeRange(index, length);
// To avoid breaking up character sequences such as 👴🏻👮🏽
range = [string rangeOfComposedCharacterSequencesForRange:range];
NSString *substring = [string substringWithRange:range];
NSString *encoded = [substring stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet];
[escaped appendString:encoded];
index += range.length;
}
return escaped;
}`</code></pre>
参数字典通过&符号拼接:
NSString * AFQueryStringFromParameters(NSDictionary *parameters) {
NSMutableArray *mutablePairs = [NSMutableArray array];
for (AFQueryStringPair *pair in AFQueryStringPairsFromDictionary(parameters)) {
[mutablePairs addObject:[pair URLEncodedStringValue]];
}
return [mutablePairs componentsJoinedByString:@"&"];
}
设置Http头部字段:
- (void)setValue:(NSString *)value
forHTTPHeaderField:(NSString *)field
{
[self.mutableHTTPRequestHeaders setValue:value forKey:field];
}
[self setValue:userAgent forHTTPHeaderField:@"User-Agent"];
KVO观察到的缓存策略，管线化，超时时间字段：
static NSArray * AFHTTPRequestSerializerObservedKeyPaths() {
static NSArray *_AFHTTPRequestSerializerObservedKeyPaths = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_AFHTTPRequestSerializerObservedKeyPaths = @[NSStringFromSelector(@selector(allowsCellularAccess)), NSStringFromSelector(@selector(cachePolicy)), NSStringFromSelector(@selector(HTTPShouldHandleCookies)), NSStringFromSelector(@selector(HTTPShouldUsePipelining)), NSStringFromSelector(@selector(networkServiceType)), NSStringFromSelector(@selector(timeoutInterval))];
});
return _AFHTTPRequestSerializerObservedKeyPaths;
}
加入观察:
self.mutableObservedChangedKeyPaths = [NSMutableSet set];
for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
if ([self respondsToSelector:NSSelectorFromString(keyPath)]) {
[self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:AFHTTPRequestSerializerObserverContext];
}
}
AFHTTPResponseSerializer子类包括AFJSONResponseSerializer，AFXMLParserResponseSerializer，AFXMLDocumentResponseSerializer，AFPropertyListResponseSerializer，AFImageResponseSerializer和AFCompoundResponseSerializer.
AFHTTPResponseSerializer及子类都实现了AFURLResponseSerialization协议.
AFJSONResponseSerializer对返回的数据解析如下:
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
return nil;
}
}
id responseObject = nil;
NSError *serializationError = nil;
// Workaround for behavior of Rails to return a single space for `head :ok` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization.
// See https://github.com/rails/rails/issues/1742
BOOL isSpace = [data isEqualToData:[NSData dataWithBytes:" " length:1]];
if (data.length > 0 && !isSpace) {
responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];
} else {
return nil;
}
if (self.removesKeysWithNullValues && responseObject) {
responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
}
if (error) {
*error = AFErrorWithUnderlyingError(serializationError, *error);
}
return responseObject;
}
JSON数据去空:
static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingOptions readingOptions) {
if ([JSONObject isKindOfClass:[NSArray class]]) {
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:[(NSArray *)JSONObject count]];
for (id value in (NSArray *)JSONObject) {
[mutableArray addObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions)];
}
return (readingOptions & NSJSONReadingMutableContainers) ? mutableArray : [NSArray arrayWithArray:mutableArray];
} else if ([JSONObject isKindOfClass:[NSDictionary class]]) {
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:JSONObject];
for (id <NSCopying> key in [(NSDictionary *)JSONObject allKeys]) {
id value = (NSDictionary *)JSONObject[key];
if (!value || [value isEqual:[NSNull null]]) {
[mutableDictionary removeObjectForKey:key];
} else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]]) {
mutableDictionary[key] = AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions);
}
}
return (readingOptions & NSJSONReadingMutableContainers) ? mutableDictionary : [NSDictionary dictionaryWithDictionary:mutableDictionary];
}
return JSONObject;
}
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