AFN作为iOS最流行的第三方库,确实为开发者省去了很多麻烦的代码,加入自己使用NSURLSeesion或者NSURLConnection来进行网络请求的话,会写很多头痛的代码,下面就对AFN的源码就行解读,话不多说,进入正题:
1.我们先看AFN的目录结构:
目录结构.png
2.一个简单的post请求可简单写:
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
[manager POST:URL parameters:parameters progress:^(NSProgress * _Nonnull uploadProgress) {
} success:^(NSURLSessionDataTask * _Nonnull task, id responseObject) {
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
}];
先到AFHTTPSessionManager类看[AFHTTPSessionManager manager]的代码如下:
+ (instancetype)manager {
return [[[self class] alloc] 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;
}
// 如果有baseurl有值且不以@"/"结尾,就加上@"/"
if ([[url path] length] > 0 && ![[url absoluteString] hasSuffix:@"/"]) {
url = [url URLByAppendingPathComponent:@""];
}
self.baseURL = url;
// 默认请求序列化方式为AFHTTPRequestSerializer
self.requestSerializer = [AFHTTPRequestSerializer serializer];
// 默认响应序列化方式为AFJSONResponseSerializer
self.responseSerializer = [AFJSONResponseSerializer serializer];
return self;
}
我们可以看到主要做了以下几件事情:
- 先利用父类的构造方法初始化,- (instancetype)initWithBaseURL:(NSURL *)url sessionConfiguration:(NSURLSessionConfiguration *)configuration.
- 设置baseURL
- 设置默认的请求和响应初始化方式
那先看看父类中的-(instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration方法做哪些事情,代码如下:
- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration {
self = [super init];
if (!self) {
return nil;
}
if (!configuration) {
configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
}
self.sessionConfiguration = configuration;
// 代理回调的队列
self.operationQueue = [[NSOperationQueue alloc] init];
// 设置最大并发数为1
self.operationQueue.maxConcurrentOperationCount = 1;
self.session = [NSURLSession sessionWithConfiguration:self.sessionConfiguration delegate:self delegateQueue:self.operationQueue];
self.responseSerializer = [AFJSONResponseSerializer serializer];
// 默认的安全策略
self.securityPolicy = [AFSecurityPolicy defaultPolicy];
#if !TARGET_OS_WATCH
self.reachabilityManager = [AFNetworkReachabilityManager sharedManager];
#endif
self.mutableTaskDelegatesKeyedByTaskIdentifier = [[NSMutableDictionary alloc] init];
// 利用NSLock保证线程安全
self.lock = [[NSLock alloc] init];
self.lock.name = AFURLSessionManagerLockName;
[self.session getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) {
for (NSURLSessionDataTask *task in dataTasks) {
// 给每一个NSURLSessionDataTask对应一个AFURLSessionManagerTaskDelegate
[self addDelegateForDataTask:task uploadProgress:nil downloadProgress:nil completionHandler:nil];
}
for (NSURLSessionUploadTask *uploadTask in uploadTasks) {
// 给每一个NSURLSessionUploadTask对应一个AFURLSessionManagerTaskDelegate
[self addDelegateForUploadTask:uploadTask progress:nil completionHandler:nil];
}
for (NSURLSessionDownloadTask *downloadTask in downloadTasks) {
// 给每一个NSURLSessionDownloadTask对应一个AFURLSessionManagerTaskDelegate
[self addDelegateForDownloadTask:downloadTask progress:nil destination:nil completionHandler:nil];
}
}];
return self;
}
这段代码里[self.session getTasksWithCompletionHandler:^(NSArray *dataTasks, NSArray *uploadTasks, NSArray *downloadTasks) { }],代码里有什么用呢?不是初始化self.session里task为空吗?,大神这样写是有原因的,原来是当后台线程回来时,不对其task重新初始化的话,会crash掉.
我们再回到AFHTTPSessionManager中- (instancetype)initWithBaseURL:(NSURL *)url sessionConfiguration:(NSURLSessionConfiguration *)configuration:方法中序列化代码是这样的:
self.requestSerializer = [AFHTTPRequestSerializer serializer];
self.responseSerializer = [AFJSONResponseSerializer serializer];
AFHTTPRequestSerializer中代码如下:
+ (instancetype)serializer {
return [[self alloc] init];
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
self.stringEncoding = NSUTF8StringEncoding;
self.mutableHTTPRequestHeaders = [NSMutableDictionary dictionary];
NSMutableArray *acceptLanguagesComponents = [NSMutableArray array];
// 设置header的语言,q为quality代表不同偏好程度,默认为1,大于0设置时才有效
[[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;
}];
[self setValue:[acceptLanguagesComponents componentsJoinedByString:@", "] forHTTPHeaderField:@"Accept-Language"];
NSString *userAgent = nil;
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
// 消除了(use of GNU ?: conditional expression extension, omitting middle operand)的警告！
#if TARGET_OS_IOS
// 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;
}
}
// 设置header的User-Agent值
[self setValue:userAgent forHTTPHeaderField:@"User-Agent"];
}
self.HTTPMethodsEncodingParametersInURI = [NSSet setWithObjects:@"GET", @"HEAD", @"DELETE", nil];
self.mutableObservedChangedKeyPaths = [NSMutableSet set];
// 将AFHTTPRequestSerializerObservedKeyPaths()中的keypath,添加到KVO中
for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
if ([self respondsToSelector:NSSelectorFromString(keyPath)]) {
[self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:AFHTTPRequestSerializerObserverContext];
}
}
return self;
}
我们知道NSMutableURLRequest是要设置header头的,这里拼接了Accept-Language和User-Agent两个参数保存在mutableHTTPRequestHeaders这个可变字典中.self.HTTPMethodsEncodingParametersInURI这个集合有GET,HEAD,DELETE三个参数,这个集合有啥用呢?因为这三种请求方式参数是拼接在URL后面的,其他请求方式是参数是设置在NSMutableURLRequest的HTTPBody中的,共给出了三种请求序列化方式:AFHTTPRequestSerializer,AFJSONRequestSerializer,AFPropertyListRequestSerializer,后两种继承于AFHTTPRequestSerializer,都遵守AFURLRequestSerialization协议.
AFHTTPRequestSerializerObservedKeyPaths()是一个C语言函数:
// 获取所观察属性的keypath
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;
}
_AFHTTPRequestSerializerObservedKeyPaths有allowsCellularAccess,cachePolicy,HTTPShouldHandleCookies,HTTPShouldUsePipelining,networkServiceType,timeoutInterval这六个元素,然后这六个元素进行KVO监听:
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(__unused id)object
change:(NSDictionary *)change
context:(void *)context
{
if (context == AFHTTPRequestSerializerObserverContext) {
if ([change[NSKeyValueChangeNewKey] isEqual:[NSNull null]]) {
[self.mutableObservedChangedKeyPaths removeObject:keyPath];
} else {
[self.mutableObservedChangedKeyPaths addObject:keyPath];
}
}
}
如果上面六个元素设置了不为null的值,就会被添加到self.mutableObservedChangedKeyPaths数组中,以在后面设置请求header里面的值.
再回到:
self.responseSerializer = [AFJSONResponseSerializer serializer];
代码中,其实现如下:
(instancetype)serializer {
return [[self alloc] init];
}
- (instancetype)init {
self = [super init];
if (!self) {
return nil;
}
// 编码方式
self.stringEncoding = NSUTF8StringEncoding;
// 正常响应的状态码的范围
self.acceptableStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(200, 100)];
self.acceptableContentTypes = nil;
return self;
}
上面代码设置正常响应的状态码为200-300,给出的响应方式有AFHTTPResponseSerializer,AFJSONResponseSerializer,AFXMLParserResponseSerializer,AFXMLDocumentResponseSerializer,AFPropertyListResponseSerializer,AFImageResponseSerializer,AFCompoundResponseSerializer后面六种方式继承于AFHTTPResponseSerializer,都遵守AFURLResponseSerialization协议.
那我们回到之前发送请求的代码:
- (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
{
// 创建一个NSURLSessionDataTask
NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"POST" URLString:URLString parameters:parameters uploadProgress:uploadProgress downloadProgress:nil success:success failure:failure];
[dataTask resume];
return dataTask;
}
这段代码将请求方式,URL字符串,参数生成一个NSURLSessionDataTask对象,然后再开启这个dataTask任务.
下面再看是怎么生成一个具体的dataTask任务的:
- (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
{
NSError *serializationError = nil;
// 创建一个NSMutableURLRequest对象
NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
if (serializationError) {
if (failure) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
// 如果设置了回调队列,回调结果就在回调队列里里执行,否则就在主队列执行
dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
failure(nil, serializationError);
});
#pragma clang diagnostic pop
}
return nil;
}
__block NSURLSessionDataTask *dataTask = nil;
// 根据前面的request生成一个dataTask
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;
}
这里主要做了两件事情:
1.根据前面传来的参数利用自己的请求序列化生成一个NSMutableURLRequest对象
2.根据前面生成NSMutableURLRequest对象生成一个NSURLSessionDataTask对象,并返回回去.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
#pragma clang diagnostic pop
这里是消除编译警告,消除(use of GNU ?: conditional expression extension, omitting middle operand)的警告.
现在去看看是怎么利用请求序列化生成一个NSMutableURLRequest对象的,代码如下:
- (NSMutableURLRequest *)requestWithMethod:(NSString *)method
URLString:(NSString *)URLString
parameters:(id)parameters
error:(NSError *__autoreleasing *)error
{
// 参数断言,debug模式下缺少参数会直接崩溃
NSParameterAssert(method);
NSParameterAssert(URLString);
NSURL *url = [NSURL URLWithString:URLString];
NSParameterAssert(url);
NSMutableURLRequest *mutableRequest = [[NSMutableURLRequest alloc] initWithURL:url];
mutableRequest.HTTPMethod = method;
for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
if ([self.mutableObservedChangedKeyPaths containsObject:keyPath]) {
[mutableRequest setValue:[self valueForKeyPath:keyPath] forKey:keyPath];
}
}
mutableRequest = [[self requestBySerializingRequest:mutableRequest withParameters:parameters error:error] mutableCopy];
return mutableRequest;
}
AFHTTPRequestSerializerObservedKeyPaths()放着allowsCellularAccess,cachePolicy,HTTPShouldHandleCookies,HTTPShouldUsePipelining,networkServiceType,timeoutInterval六个请求序列化的属性,如果前面六个属性设置不为null的值,那么这个属性就会加到mutableObservedChangedKeyPaths这个集合中.然后将这些值设置在mutableRequest中.
由于给出的请求序列化方式都遵守AFURLRequestSerialization协议,协议中有个
- (nullable NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
withParameters:(nullable id)parameters
error:(NSError * _Nullable __autoreleasing *)error
方法.再看看其的具体实现:
#pragma mark - AFURLRequestSerialization
- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
withParameters:(id)parameters
error:(NSError *__autoreleasing *)error
{
NSParameterAssert(request);
NSMutableURLRequest *mutableRequest = [request mutableCopy];
[self.HTTPRequestHeaders enumerateKeysAndObjectsUsingBlock:^(id field, id value, BOOL * __unused stop) {
// 遍历HTTPRequestHeaders字典,如果request中的field没有值,就设置值
if (![request valueForHTTPHeaderField:field]) {
[mutableRequest setValue:value forHTTPHeaderField:field];
}
}];
NSString *query = nil;
if (parameters) {
// 自定义的queryString序列化方式
if (self.queryStringSerialization) {
NSError *serializationError;
query = self.queryStringSerialization(request, parameters, &serializationError);
if (serializationError) {
if (error) {
*error = serializationError;
}
return nil;
}
} else {
// 默认的queryString序列化方式
switch (self.queryStringSerializationStyle) {
case AFHTTPRequestQueryStringDefaultStyle:
query = AFQueryStringFromParameters(parameters);
break;
}
}
}
// 如果method为get,head,delete时,将query拼接到URL后面
if ([self.HTTPMethodsEncodingParametersInURI containsObject:[[request HTTPMethod] uppercaseString]]) {
if (query && query.length > 0) {
mutableRequest.URL = [NSURL URLWithString:[[mutableRequest.URL absoluteString] stringByAppendingFormat:mutableRequest.URL.query ? @"&%@" : @"?%@", query]];
}
} else {
// 如果query为空, query设置为空字符串
if (!query) {
query = @"";
}
// 设置headerField的Content-Type
if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
[mutableRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
}
// 将method为get,head,delete外的query设置在HTTPBody中
[mutableRequest setHTTPBody:[query dataUsingEncoding:self.stringEncoding]];
}
return mutableRequest;
}
上面主要做了一下几件事情:
- 给mutableRequest设置header头.
- 根据queryString序列化方式生成一个query的字符串.
- 然后根据请求的方式拼接query:如果是get,head,delete方式就直接拼接在url后面,其他方式设置在HTTPBody中.
下面看看怎么生成queryString的:
NSString * AFQueryStringFromParameters(NSDictionary *parameters) {
NSMutableArray *mutablePairs = [NSMutableArray array];
for (AFQueryStringPair *pair in AFQueryStringPairsFromDictionary(parameters)) {
[mutablePairs addObject:[pair URLEncodedStringValue]];
}
return [mutablePairs componentsJoinedByString:@"&"];
}
NSArray * AFQueryStringPairsFromDictionary(NSDictionary *dictionary) {
return AFQueryStringPairsFromKeyAndValue(nil, dictionary);
}
NSArray * AFQueryStringPairsFromKeyAndValue(NSString *key, id value) {
NSMutableArray *mutableQueryStringComponents = [NSMutableArray array];
// 创个一个排序的sortDescriptor
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"description" ascending:YES selector:@selector(compare:)];
if ([value isKindOfClass:[NSDictionary class]]) {
NSDictionary *dictionary = value;
for (id nestedKey in [dictionary.allKeys sortedArrayUsingDescriptors:@[ sortDescriptor ]]) {
id nestedValue = dictionary[nestedKey];
if (nestedValue) {
[mutableQueryStringComponents addObjectsFromArray:AFQueryStringPairsFromKeyAndValue((key ? [NSString stringWithFormat:@"%@[%@]", key, nestedKey] : nestedKey), nestedValue)];
}
}
} else if ([value isKindOfClass:[NSArray class]]) {
NSArray *array = value;
for (id nestedValue in array) {
[mutableQueryStringComponents addObjectsFromArray:AFQueryStringPairsFromKeyAndValue([NSString stringWithFormat:@"%@[]", key], nestedValue)];
}
} else if ([value isKindOfClass:[NSSet class]]) {
NSSet *set = value;
for (id obj in [set sortedArrayUsingDescriptors:@[ sortDescriptor ]]) {
[mutableQueryStringComponents addObjectsFromArray:AFQueryStringPairsFromKeyAndValue(key, obj)];
}
} else {
[mutableQueryStringComponents addObject:[[AFQueryStringPair alloc] initWithField:key value:value]];
}
return mutableQueryStringComponents;
}
上面是三个c语言的函数,根据传进来的参数来生成一个queryString.
然后递归调用AFQueryStringFromParameters方法,直到解析NSDictionary, NSArray, NSSet到以外的元素.
AFQueryStringPair类的代码如下:
@interface AFQueryStringPair : NSObject
@property (readwrite, nonatomic, strong) id field;
@property (readwrite, nonatomic, strong) id value;
- (instancetype)initWithField:(id)field value:(id)value;
- (NSString *)URLEncodedStringValue;
@end
@implementation AFQueryStringPair
- (instancetype)initWithField:(id)field value:(id)value {
self = [super init];
if (!self) {
return nil;
}
self.field = field;
self.value = value;
return self;
}
// 对field和value进行编码
- (NSString *)URLEncodedStringValue {
if (!self.value || [self.value isEqual:[NSNull null]]) {
return AFPercentEscapedStringFromString([self.field description]);
} else {
return [NSString stringWithFormat:@"%@=%@", AFPercentEscapedStringFromString([self.field description]), AFPercentEscapedStringFromString([self.value description])];
}
}
@end
AFPercentEscapedStringFromString()方法代码如下:
NSString * AFPercentEscapedStringFromString(NSString *string) {
static NSString * const kAFCharactersGeneralDelimitersToEncode = @":#[]@"; // 根据RFC 3986不包含?和/两个字符
static NSString * const kAFCharactersSubDelimitersToEncode = @"!$&'()*+,;=";
NSMutableCharacterSet * allowedCharacterSet = [[NSCharacterSet URLQueryAllowedCharacterSet] mutableCopy];
[allowedCharacterSet removeCharactersInString:[kAFCharactersGeneralDelimitersToEncode stringByAppendingString:kAFCharactersSubDelimitersToEncode]];
// 这里为什么要一次性最大编码长度为50?因为在iOS8.1,8.2,系统有个bug,如果一次编码几百个中文字符,会导致会因为内存分配错误,而导致崩溃
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);
// 避免多字节的字符,比如emoji等,被分隔开
range = [string rangeOfComposedCharacterSequencesForRange:range];
NSString *substring = [string substringWithRange:range];
NSString *encoded = [substring stringByAddingPercentEncodingWithAllowedCharacters:allowedCharacterSet];
[escaped appendString:encoded];
index += range.length;
}
return escaped;
}
以上几步总结起来就是下面的例子:
@{
@"a" : @"a",
@"b": @{@"a": @"b", @"c": @"d"},
@"c": @[@"a", @"b"],
@"d": [NSSet setWithObjects:@"a", @"b", nil]
}
=> a=a&b[a]=b&b[c]=d&c[]=a&c[]=b&d=a&d=b
好了前面已经生成了一个NSMutableURLRequest对象,现在根据这个对象生成一个dataTask,代码如下:
- (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;
// iOS8以下会并发创建的tasks,会出现相同的taskIdentifier,导致completionHandlers不正确
url_session_manager_create_task_safely(^{
dataTask = [self.session dataTaskWithRequest:request];
});
// 将AFURLSessionManagerTaskDelegate对象和一个dataTask对象一一对应.
[self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler];
return dataTask;
}
这里用了一个了安全的处理方法,由于苹果iOS8创建dataTask会并发的创建,会出现相同的taskIdentifier,而一个taskIdentifier对应一个回调的completionHandlers所以会出现错误.
根据前面的代码我们已经生成了一个dataTask,并将这个任务resume了.其实AFN中还做了当一个dataTask resume或者suspend之后,给外界发出了一个通知,供外界监听.所以我们不仅要resume和suspend的系统的实现,还要给外界发出通知,供外界监听.所以我们需要对dataTask类的resume和suspend进行方法调配(method swizzle),但是NSURLSessionTasks是一个类簇,我们实际创建任务不是这个类,这需要几条是需要确定的:
// NSURLSessionTasks是在类簇实现的,意味着API中请求的类型和你得到类型并不一致
// 调用[NSURLSessionTask class]并不管用,你需要询问NSURLSession是哪个类创建了这个对象
// 在iOS7中 localDataTask 是一个 __NSCFLocalDataTask类型,继承于__NSCFLocalSessionTask,而__NSCFLocalSessionTask继承于__NSCFURLSessionTask
// 在iOS8中,localDataTask是一个__NSCFLocalDataTask类型,继承于__NSCFLocalSessionTask,而__NSCFLocalSessionTask继承于NSURLSessionTask
// 在iOS7中,__NSCFLocalSessionTask和__NSCFURLSessionTask是唯一的两个类实现了resume和suspend两个方法,__NSCFLocalSessionTask不会调用父类的实现,意味着这两个类需要被swizzled
// 在iOS8中,NSURLSessionTask 是唯一的类实现resume和suspend方法,这意味着这一唯一的一个类需要被swizzled
// 因为NSURLSessionTask在每一个iOS版本不涉及到类的层级结构,所以给一个dummy class添加swizzled methods来管理他们
// 一些假设:
// resume或者suspend方法没有调用super,如果这会在将来的iOS版本中变化,我们需要处理它
// 没有后台任务类复写resume或者suspend
// 当前的解决方法
1.获取一个__NSCFLocalDataTask实例,通过NSURLSession的一个data task来获取
2.通过af_resume指针指向原来的实现
3.检查当前的类是否实现resume方法,如果实现,继续第四部
4.获取当前的类的父类
5.获取当前类的的resume的当前实现的指针
6.获取当前类的父类resume的当前实现的指针
7.如果当前的类resume不等于父类的resume实现,并且当前resume的实现不同于af_resume的实现,然后就行swizzle the methods
8.设置当前的父类为自己,并重复3-8
所以这里借助了一个_AFURLSessionTaskSwizzling这样的一个dummy class来进行method swizzled.具体实现如下:
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));
}
static NSString * const AFNSURLSessionTaskDidResumeNotification = @"com.alamofire.networking.nsurlsessiontask.resume";
static NSString * const AFNSURLSessionTaskDidSuspendNotification = @"com.alamofire.networking.nsurlsessiontask.suspend";
@interface _AFURLSessionTaskSwizzling : NSObject
@end
@implementation _AFURLSessionTaskSwizzling
+ (void)load {
// 返回一个预设配置，没有持久性存储的缓存，Cookie或证书。这对于实现像"秘密浏览"功能的功能来说，是很理想的。
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration ephemeralSessionConfiguration];
NSURLSession * session = [NSURLSession sessionWithConfiguration:configuration];
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnonnull"
NSURLSessionDataTask *localDataTask = [session dataTaskWithURL:nil];
#pragma clang diagnostic pop
IMP originalAFResumeIMP = method_getImplementation(class_getInstanceMethod([self class], @selector(af_resume)));
Class currentClass = [localDataTask class];
while (class_getInstanceMethod(currentClass, @selector(resume))) {
Class superClass = [currentClass superclass];
IMP classResumeIMP = method_getImplementation(class_getInstanceMethod(currentClass, @selector(resume)));
IMP superclassResumeIMP = method_getImplementation(class_getInstanceMethod(superClass, @selector(resume)));
if (classResumeIMP != superclassResumeIMP &&
originalAFResumeIMP != classResumeIMP) {
[self swizzleResumeAndSuspendMethodForClass:currentClass];
}
currentClass = [currentClass superclass];
}
[localDataTask cancel];
[session finishTasksAndInvalidate];
}
}
+ (void)swizzleResumeAndSuspendMethodForClass:(Class)theClass {
Method afResumeMethod = class_getInstanceMethod(self, @selector(af_resume));
Method afSuspendMethod = class_getInstanceMethod(self, @selector(af_suspend));
if (af_addMethod(theClass, @selector(af_resume), afResumeMethod)) {
af_swizzleSelector(theClass, @selector(resume), @selector(af_resume));
}
if (af_addMethod(theClass, @selector(af_suspend), afSuspendMethod)) {
af_swizzleSelector(theClass, @selector(suspend), @selector(af_suspend));
}
}
- (NSURLSessionTaskState)state {
NSAssert(NO, @"State method should never be called in the actual dummy class");
return NSURLSessionTaskStateCanceling;
}
// 在原来的resume实现的基础上,发送了AFNSURLSessionTaskDidResumeNotification的通知
- (void)af_resume {
NSAssert([self respondsToSelector:@selector(state)], @"Does not respond to state");
NSURLSessionTaskState state = [self state];
[self af_resume];
if (state != NSURLSessionTaskStateRunning) {
[[NSNotificationCenter defaultCenter] postNotificationName:AFNSURLSessionTaskDidResumeNotification object:self];
}
}
// 在原来的suspend的实现的基础上,发送了一个AFNSURLSessionTaskDidSuspendNotification通知
- (void)af_suspend {
NSAssert([self respondsToSelector:@selector(state)], @"Does not respond to state");
NSURLSessionTaskState state = [self state];
[self af_suspend];
if (state != NSURLSessionTaskStateSuspended) {
[[NSNotificationCenter defaultCenter] postNotificationName:AFNSURLSessionTaskDidSuspendNotification object:self];
}
}
@end
这里发出的通知,给外界提供了监听,比如AFN中的为UIKit添加的分类,都需要监听这两个通知.前面的dataTask创建好了,并恢复了任务,现在就看看回调的代码:
#pragma mark - NSURLSessionTaskDelegate
- (void)URLSession:(__unused NSURLSession *)session
task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error
{
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu"
__strong AFURLSessionManager *manager = self.manager;
__block id responseObject = nil;
__block NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
userInfo[AFNetworkingTaskDidCompleteResponseSerializerKey] = manager.responseSerializer;
//Performance Improvement from #2672
NSData *data = nil;
if (self.mutableData) {
data = [self.mutableData copy];
// 解除self.mutableData的引用,释放一些内存
self.mutableData = nil;
}
if (self.downloadFileURL) {
userInfo[AFNetworkingTaskDidCompleteAssetPathKey] = self.downloadFileURL;
} else if (data) {
userInfo[AFNetworkingTaskDidCompleteResponseDataKey] = data;
}
// 如果错误
if (error) {
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 {
// 如果没有错误,进行响应序列化返回一个responseObject
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(), ^{
if (self.completionHandler) {
self.completionHandler(task.response, responseObject, serializationError);
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingTaskDidCompleteNotification object:task userInfo:userInfo];
});
});
});
}
#pragma clang diagnostic pop
}
上面的代码如果有错误,就直接返回,否则就行响应序列化,返回responseObject,下面去响应序列化的代码如下:
#pragma mark - AFURLResponseSerialization
- (id)responseObjectForResponse:(NSURLResponse *)response
data:(NSData *)data
error:(NSError *__autoreleasing *)error
{
// 验证response是否合法
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;
}
// 移除值为nil或者null的key
if (self.removesKeysWithNullValues && responseObject) {
responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
}
if (error) {
*error = AFErrorWithUnderlyingError(serializationError, *error);
}
return responseObject;
}
#pragma mark -
- (BOOL)validateResponse:(NSHTTPURLResponse *)response
data:(NSData *)data
error:(NSError * __autoreleasing *)error
{
BOOL responseIsValid = YES;
NSError *validationError = nil;
if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]] &&
!([response MIMEType] == nil && [data length] == 0)) {
// 如果是AFJSONResponseSerializer 的话,接受的contentTypes只有@"application/json", @"text/json", @"text/javascript"三种,如果返回的contentType在接受的类型中,直接抛出错误;
if ([data length] > 0 && [response URL]) {
NSMutableDictionary *mutableUserInfo = [@{
NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
NSURLErrorFailingURLErrorKey:[response URL],
AFNetworkingOperationFailingURLResponseErrorKey: response,
} mutableCopy];
if (data) {
mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
}
validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:mutableUserInfo], validationError);
}
responseIsValid = NO;
}
// 如果返回的状态码不在(200-300)之间,抛出错误
if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode] && [response URL]) {
NSMutableDictionary *mutableUserInfo = [@{
NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
NSURLErrorFailingURLErrorKey:[response URL],
AFNetworkingOperationFailingURLResponseErrorKey: response,
} mutableCopy];
if (data) {
mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
}
validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:mutableUserInfo], validationError);
responseIsValid = NO;
}
}
if (error && !responseIsValid) {
*error = validationError;
}
return responseIsValid;
}
上面的代码主要做了两件事:
1.验证response是否合法,接受的类型是否匹配,状态码是否在可接受的范围.
2.进行json序列化
通过前面的介绍,梳理了一个post请求,AFN帮我们做了那些事,大神的编程思想确实牛逼,只有不断阅读大神的源码,才能对编程更深的认识.