AFNetworking

AFHTTPRequestSerializer 请求序列化

初始化，大概干了这么些事情

• Accept-Language ：前五种语言
• User-Agent ：项目名称？：bundleID 版本号 model ios 系统号 scale
• 监听暴漏在外部的六个属性

 self.stringEncoding = NSUTF8StringEncoding;
    self.mutableHTTPRequestHeaders = [NSMutableDictionary dictionary];
    self.requestHeaderModificationQueue = dispatch_queue_create("requestHeaderModificationQueue", DISPATCH_QUEUE_CONCURRENT);
    NSMutableArray *acceptLanguagesComponents = [NSMutableArray array];
    ///获取前五中语言
    [[NSLocale preferredLanguages] enumerateObjectsUsingBlock:^(NSString * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        float q = 1.0f - (idx *0.1f);
        [acceptLanguagesComponents addObject:[NSString stringWithFormat:@"%@;q=%0.1g",obj,q]];
        *stop = q<=0.5f;
    }];
    ///设置前五种语言
    [self setValue:[acceptLanguagesComponents componentsJoinedByString:@", "] forHTTPHeaderField:@"Accept-Language"];
    NSString *userAgent = nil;
#if TARGET_OS_IOS
    ///ebooksystem       /4.0.0 (iPhone; iOS 13.3; Scale/2.00) ios.zaxue.zaxue_ios
    ///项目名称？：bundleID 版本号   model   ios 系统号 scale
    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
    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"];
    }
    self.HTTPMethodsEncodingParametersInURI = [NSSet setWithObjects:@"GET",@"HEAD",@"DELETE",nil];
    self.mutableObservedChangedKeyPaths = [NSMutableSet set];
    ///监听六个属性
    for (NSString *keyPath in AFHTTPRequestSerializerObservedKeyPaths()) {
        if ([self respondsToSelector:NSSelectorFromString(keyPath)]) {
            [self addObserver:self forKeyPath:keyPath options:NSKeyValueObservingOptionNew context:AFHTTPRequestSerializerObserverContext];
        }
    }

requestWithMethod

数据放在contentType中，直接用body上传

 - (NSMutableURLRequest *)requestWithMethod:(NSString *)method
 URLString:(NSString *)URLString
parameters:(id)parameters error:(NSError *__autoreleasing *)error

生成request的基本方法

- (NSURLRequest *)requestBySerializingRequest:(NSURLRequest *)request
                               withParameters:(id)parameters
                                        error:(NSError *__autoreleasing *)error

multipart 流传输 用于大文件

Content-Type:multipart/form-data;boundary=

- (NSMutableURLRequest *)multipartFormRequestWithMethod:(NSString *)method
                URLString:(NSString *)URLString
               parameters:(NSDictionary *)parameters
constructingBodyWithBlock:(void (^)(id <AFMultipartFormData> formData))block
                                                  error:(NSError *__autoreleasing *)error { NSParameterAssert(method);
    NSParameterAssert(![method isEqualToString:@"GET"] && ![method isEqualToString:@"HEAD"]);
    NSMutableURLRequest *mutableRequest = [self requestWithMethod:method URLString:URLString parameters:nil error:error];
    
    __block AFStreamingMultipartFormData *formData = [[AFStreamingMultipartFormData alloc] initWithURLRequest:mutableRequest stringEncoding:NSUTF8StringEncoding];
//将传入字典转为AFQueryStringPair
    if (parameters) {
        for (AFQueryStringPair *pair in AFQueryStringPairsFromDictionary(parameters)) {
            NSData *data = nil;
            if ([pair.value isKindOfClass:[NSData class]]) {
                data = pair.value;
            } else if ([pair.value isEqual:[NSNull null]]) {
                data = [NSData data];
            } else {
                data = [[pair.value description]dataUsingEncoding:self.stringEncoding];
            }
///拼接到data中
if (data) {
                [formData appendPartWithFormData:data name:[pair.field description]];
            }
        }
    }
    if (block) {
        block(formData);
    }
    ///返回最终拼好流和body的 request
    return [formData requestByFinalizingMultipartFormData];
}

来进一步分析里面干了些什么

1. 先根据requestWithMethod:method生成一个request

 NSMutableURLRequest *mutableRequest = [self requestWithMethod:method URLString:URLString parameters:nil error:error];

 __block AFStreamingMultipartFormData *formData = [[AFStreamingMultipartFormData alloc] initWithURLRequest:mutableRequest stringEncoding:NSUTF8StringEncoding];

AFStreamingMultipartFormData

AFStreamingMultipartFormData干了些什么呢？

1. 核心方法是这个，设置BodyStream ，其中 self.boundary 和 bodyStream是其两个属性，返回设置bodyStream 的 request

- (NSMutableURLRequest *)requestByFinalizingMultipartFormData

appendPartWithFileURL 是谁调用呢？

2. 遵守 AFMultipartFormData 的代理方 外部调用 appendPartWithFileData 方法传入Data数据并将数据转为AFHTTPBodyPart 模型

然后appendHTTPBodyPart 将body 加到 AFMultipartBodyStream 的 HTTPBodyParts body数组中

AFMultipartBodyStream

用于存放AFHTTPBodyPart的数组
@property (readwrite, nonatomic, strong) NSMutableArray *HTTPBodyParts;

外部暴漏的方法

初始化stream
- (instancetype)initWithStringEncoding:(NSStringEncoding)encoding;
///HTTPBodyParts的第一个元素设置开始属性为YES，把最后一个元素设置结束属性为YES  AFStreamingMultipartFormData返回Request时 和打开流 时 会调用
- (void)setInitialAndFinalBoundaries;
/// HTTPBodyParts 添加 HTTPBodyParts
- (void)appendHTTPBodyPart:(AFHTTPBodyPart *)bodyPart;

///重写了NSInputStream的 读取拼接数据
- (NSInteger)read:(uint8_t *)buffer
        maxLength:(NSUInteger)length
///拼接下一段body

AFHTTPBodyPart

外部暴漏方法

///转移到下一个阶段
- (BOOL)transitionToNextPhase;
///模型拼接Data数据
- (NSInteger)readData:(NSData *)data
           intoBuffer:(uint8_t *)buffer
            maxLength:(NSUInteger)length;
- (BOOL)transitionToNextPhase
 对Multipart请求体各部分（初始边界、头部、内容数据实体、结束边界）做拼接和读取的封装

AFHTTPRequestSerializer逻辑图