該文章閱讀的AFNetworking的版本為3.2.0。

AFHTTPSessionManager類是我們平常使用AFNetworking用的最多的一個類，這個類是AFURLSessionManager類的子類，它封裝了HTTP請求的建立方法。所以通過前一篇文章對AFURLSessionManager的閱讀，我們再看這個類就會容易很多。

1.介面檔案

1.1.屬性

/**
 用於構造NSURL物件的+URLWithString:relativeToURL:方法中相對路徑
 */
@property (readonly, nonatomic, strong, nullable) NSURL *baseURL;

/**
 請求序列化物件，預設是AFHTTPRequestSerializer物件
 */
@property (nonatomic, strong) AFHTTPRequestSerializer <AFURLRequestSerialization> * requestSerializer;

/**
 響應序列化物件，預設是AFJSONResponseSerializer物件
 */
@property (nonatomic, strong) AFHTTPResponseSerializer <AFURLResponseSerialization> * responseSerializer;

/**
 用於確保安全連線的安全策略物件，預設為`defaultPolicy`
 */
@property (nonatomic, strong) AFSecurityPolicy *securityPolicy;
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1.2.方法

/**
 例項化工廠方法
 */
+ (instancetype)manager;

/**
 以指定基本路徑初始化物件
 */
- (instancetype)initWithBaseURL:(nullable NSURL *)url;

/**
 以指定基本路徑和網路會話配置物件初始化物件
 */
- (instancetype)initWithBaseURL:(nullable NSURL *)url
           sessionConfiguration:(nullable NSURLSessionConfiguration *)configuration NS_DESIGNATED_INITIALIZER;

/**
 建立執行一個GET請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)GET:(NSString *)URLString
                   parameters:(nullable id)parameters
                      success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                      failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure DEPRECATED_ATTRIBUTE;


/**
 建立執行一個GET請求的NSURLSessionDataTask物件，帶有進度回撥，但是這個進度回撥是在AFURLSessionManager類中建立的那個操作佇列中，並不在主佇列中
 */
- (nullable NSURLSessionDataTask *)GET:(NSString *)URLString
                            parameters:(nullable id)parameters
                              progress:(nullable void (^)(NSProgress *downloadProgress))downloadProgress
                               success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                               failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個HEAD請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)HEAD:(NSString *)URLString
                    parameters:(nullable id)parameters
                       success:(nullable void (^)(NSURLSessionDataTask *task))success
                       failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個POST請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(nullable id)parameters
                       success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                       failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure DEPRECATED_ATTRIBUTE;

/**
 建立執行一個POST請求的NSURLSessionDataTask物件，帶有進度回撥，但是這個進度回撥是在AFURLSessionManager類中建立的那個操作佇列中，並不在主佇列中
 */
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
                             parameters:(nullable id)parameters
                               progress:(nullable void (^)(NSProgress *uploadProgress))uploadProgress
                                success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                                failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個multipart/form-data的POST請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(nullable id)parameters
     constructingBodyWithBlock:(nullable void (^)(id <AFMultipartFormData> formData))block
                       success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                       failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure DEPRECATED_ATTRIBUTE;

/**
 建立執行一個multipart/form-data的POST請求的NSURLSessionDataTask物件，帶有進度回撥，但是這個進度回撥是在AFURLSessionManager類中建立的那個操作佇列中，並不在主佇列中
 */
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
                             parameters:(nullable id)parameters
              constructingBodyWithBlock:(nullable void (^)(id <AFMultipartFormData> formData))block
                               progress:(nullable void (^)(NSProgress *uploadProgress))uploadProgress
                                success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                                failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個PUT請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)PUT:(NSString *)URLString
                   parameters:(nullable id)parameters
                      success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                      failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個PATCH請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)PATCH:(NSString *)URLString
                     parameters:(nullable id)parameters
                        success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                        failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;

/**
 建立執行一個DELETE請求的NSURLSessionDataTask物件
 */
- (nullable NSURLSessionDataTask *)DELETE:(NSString *)URLString
                      parameters:(nullable id)parameters
                         success:(nullable void (^)(NSURLSessionDataTask *task, id _Nullable responseObject))success
                         failure:(nullable void (^)(NSURLSessionDataTask * _Nullable task, NSError *error))failure;
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2.實現檔案

2.1.分類

/**
 用來儲存傳入的基本路徑
 */
@property (readwrite, nonatomic, strong) NSURL *baseURL;
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2.2.關鍵字

@dynamic responseSerializer;
@dynamic securityPolicy;
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@dynamic這個關鍵字告訴編譯器不用幫我實現getter和setter。所以在下面的方法中我們就可以看到手動實現的setter，但是沒有發現手動實現的getter，難道在呼叫getter的時候不會崩潰嗎？其實是不會的，因為這個屬性是繼承自其父類，在其父類中已經實現了它的getter，在呼叫子類的getter時就是呼叫其父類的。

2.3.方法實現

• 初始化方法

+ (instancetype)manager {
    // 不指定基本路徑
    return [[[self class] alloc] initWithBaseURL:nil];
}

- (instancetype)init {
    // 不指定基本路徑
    return [self initWithBaseURL:nil];
}

- (instancetype)initWithBaseURL:(NSURL *)url {
    // 指定基本路徑，不指定網路會話配置物件
    return [self initWithBaseURL:url sessionConfiguration:nil];
}

- (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration {
    // 不指定基本路徑，指定網路會話配置物件
    return [self initWithBaseURL:nil sessionConfiguration:configuration];
}

- (instancetype)initWithBaseURL:(NSURL *)url
           sessionConfiguration:(NSURLSessionConfiguration *)configuration
{
    // 先呼叫其父類AFURLSessionManager的初始化方法
    self = [super initWithSessionConfiguration:configuration];
    if (!self) {
        return nil;
    }

    // 如果有效的url後沒有正斜線“/”就新增上正斜線“/”
    // 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:@""];
    }

    // 儲存傳入的基本路徑
    self.baseURL = url;

    // 設定請求和響應序列化物件
    self.requestSerializer = [AFHTTPRequestSerializer serializer];
    self.responseSerializer = [AFJSONResponseSerializer serializer];

    return self;
}
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• 手動實現的setter

- (void)setRequestSerializer:(AFHTTPRequestSerializer <AFURLRequestSerialization> *)requestSerializer {
    // 在debug下，缺少引數就crash
    NSParameterAssert(requestSerializer);

    // 儲存引數
    _requestSerializer = requestSerializer;
}

- (void)setResponseSerializer:(AFHTTPResponseSerializer <AFURLResponseSerialization> *)responseSerializer {
    // 在debug下，缺少引數就crash
    NSParameterAssert(responseSerializer);

    // 呼叫其父類的setter
    [super setResponseSerializer:responseSerializer];
}

- (void)setSecurityPolicy:(AFSecurityPolicy *)securityPolicy {
    // 如果安全策略是要進行驗證，但是傳入的基本路徑不是以https開頭，就會丟擲異常
    if (securityPolicy.SSLPinningMode != AFSSLPinningModeNone && ![self.baseURL.scheme isEqualToString:@"https"]) {
        NSString *pinningMode = @"Unknown Pinning Mode";
        switch (securityPolicy.SSLPinningMode) {
            case AFSSLPinningModeNone:        pinningMode = @"AFSSLPinningModeNone"; break;
            case AFSSLPinningModeCertificate: pinningMode = @"AFSSLPinningModeCertificate"; break;
            case AFSSLPinningModePublicKey:   pinningMode = @"AFSSLPinningModePublicKey"; break;
        }
        NSString *reason = [NSString stringWithFormat:@"A security policy configured with `%@` can only be applied on a manager with a secure base URL (i.e. https)", pinningMode];
        @throw [NSException exceptionWithName:@"Invalid Security Policy" reason:reason userInfo:nil];
    }

    // 呼叫父類的setter
    [super setSecurityPolicy:securityPolicy];
}
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• 建立請求的公共方法

- (NSURLSessionDataTask *)GET:(NSString *)URLString
                   parameters:(id)parameters
                      success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                      failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{

    // 呼叫下面的方法
    return [self GET:URLString parameters:parameters progress:nil success:success failure:failure];
}

- (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
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET"
                                                        URLString:URLString
                                                       parameters:parameters
                                                   uploadProgress:nil
                                                 downloadProgress:downloadProgress
                                                          success:success
                                                          failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)HEAD:(NSString *)URLString
                    parameters:(id)parameters
                       success:(void (^)(NSURLSessionDataTask *task))success
                       failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"HEAD" URLString:URLString parameters:parameters uploadProgress:nil downloadProgress:nil success:^(NSURLSessionDataTask *task, __unused id responseObject) {
        if (success) {
            success(task);
        }
    } failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(id)parameters
                       success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                       failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 呼叫下面的方法
    return [self POST:URLString parameters:parameters progress:nil success:success failure:failure];
}

- (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
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"POST" URLString:URLString parameters:parameters uploadProgress:uploadProgress downloadProgress:nil success:success failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(nullable id)parameters
     constructingBodyWithBlock:(nullable void (^)(id<AFMultipartFormData> _Nonnull))block
                       success:(nullable void (^)(NSURLSessionDataTask * _Nonnull, id _Nullable))success
                       failure:(nullable void (^)(NSURLSessionDataTask * _Nullable, NSError * _Nonnull))failure
{
    // 呼叫下面的方法
    return [self POST:URLString parameters:parameters constructingBodyWithBlock:block progress:nil success:success failure:failure];
}

- (NSURLSessionDataTask *)POST:(NSString *)URLString
                    parameters:(id)parameters
     constructingBodyWithBlock:(void (^)(id <AFMultipartFormData> formData))block
                      progress:(nullable void (^)(NSProgress * _Nonnull))uploadProgress
                       success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                       failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 例項化NSMutableURLRequest物件
    NSError *serializationError = nil;
    NSMutableURLRequest *request = [self.requestSerializer multipartFormRequestWithMethod:@"POST" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters constructingBodyWithBlock:block error:&serializationError];
    // 如果例項化出錯就回撥錯誤
    if (serializationError) {
        if (failure) {
            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
                failure(nil, serializationError);
            });
        }

        return nil;
    }

    // 例項化NSURLSessionDataTask物件
    __block NSURLSessionDataTask *task = [self uploadTaskWithStreamedRequest:request progress:uploadProgress completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
        if (error) {
            if (failure) {
                failure(task, error);
            }
        } else {
            if (success) {
                success(task, responseObject);
            }
        }
    }];

    // 啟動task
    [task resume];

    return task;
}

- (NSURLSessionDataTask *)PUT:(NSString *)URLString
                   parameters:(id)parameters
                      success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                      failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PUT" URLString:URLString parameters:parameters uploadProgress:nil downloadProgress:nil success:success failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)PATCH:(NSString *)URLString
                     parameters:(id)parameters
                        success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                        failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"PATCH" URLString:URLString parameters:parameters uploadProgress:nil downloadProgress:nil success:success failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (NSURLSessionDataTask *)DELETE:(NSString *)URLString
                      parameters:(id)parameters
                         success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                         failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    // 例項化NSURLSessionDataTask物件
    NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"DELETE" URLString:URLString parameters:parameters uploadProgress:nil downloadProgress:nil success:success failure:failure];

    // 啟動dataTask
    [dataTask resume];

    return dataTask;
}

- (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
{
    // 例項化NSMutableURLRequest物件
    NSError *serializationError = nil;
    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError];
    // 如果例項化出錯就回撥錯誤
    if (serializationError) {
        if (failure) {
            dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{
                failure(nil, serializationError);
            });
        }

        return nil;
    }

    // 例項化NSURLSessionDataTask物件
    __block NSURLSessionDataTask *dataTask = nil;
    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;
}
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• NSObject方法

- (NSString *)description {
    // 定製列印資料
    return [NSString stringWithFormat:@"<%@: %p, baseURL: %@, session: %@, operationQueue: %@>", NSStringFromClass([self class]), self, [self.baseURL absoluteString], self.session, self.operationQueue];
}
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• NSSecureCoding方法實現

+ (BOOL)supportsSecureCoding {
    return YES;
}

- (instancetype)initWithCoder:(NSCoder *)decoder {
    NSURL *baseURL = [decoder decodeObjectOfClass:[NSURL class] forKey:NSStringFromSelector(@selector(baseURL))];
    NSURLSessionConfiguration *configuration = [decoder decodeObjectOfClass:[NSURLSessionConfiguration class] forKey:@"sessionConfiguration"];
    if (!configuration) {
        NSString *configurationIdentifier = [decoder decodeObjectOfClass:[NSString class] forKey:@"identifier"];
        if (configurationIdentifier) {
#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 80000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1100)
            configuration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:configurationIdentifier];
#else
            configuration = [NSURLSessionConfiguration backgroundSessionConfiguration:configurationIdentifier];
#endif
        }
    }

    self = [self initWithBaseURL:baseURL sessionConfiguration:configuration];
    if (!self) {
        return nil;
    }

    self.requestSerializer = [decoder decodeObjectOfClass:[AFHTTPRequestSerializer class] forKey:NSStringFromSelector(@selector(requestSerializer))];
    self.responseSerializer = [decoder decodeObjectOfClass:[AFHTTPResponseSerializer class] forKey:NSStringFromSelector(@selector(responseSerializer))];
    AFSecurityPolicy *decodedPolicy = [decoder decodeObjectOfClass:[AFSecurityPolicy class] forKey:NSStringFromSelector(@selector(securityPolicy))];
    if (decodedPolicy) {
        self.securityPolicy = decodedPolicy;
    }

    return self;
}

- (void)encodeWithCoder:(NSCoder *)coder {
    [super encodeWithCoder:coder];

    [coder encodeObject:self.baseURL forKey:NSStringFromSelector(@selector(baseURL))];
    if ([self.session.configuration conformsToProtocol:@protocol(NSCoding)]) {
        [coder encodeObject:self.session.configuration forKey:@"sessionConfiguration"];
    } else {
        [coder encodeObject:self.session.configuration.identifier forKey:@"identifier"];
    }
    [coder encodeObject:self.requestSerializer forKey:NSStringFromSelector(@selector(requestSerializer))];
    [coder encodeObject:self.responseSerializer forKey:NSStringFromSelector(@selector(responseSerializer))];
    [coder encodeObject:self.securityPolicy forKey:NSStringFromSelector(@selector(securityPolicy))];
}
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關於NSSecureCoding代理方法的實現在AFNetworking原始碼閱讀（二）——從AFURLRequestSerialization入手這篇文章中的4.1.2.4.7 NSSecureCoding協議方法的實現段落已經介紹過。

• NSCopying方法實現

- (instancetype)copyWithZone:(NSZone *)zone {
    AFHTTPSessionManager *HTTPClient = [[[self class] allocWithZone:zone] initWithBaseURL:self.baseURL sessionConfiguration:self.session.configuration];

    HTTPClient.requestSerializer = [self.requestSerializer copyWithZone:zone];
    HTTPClient.responseSerializer = [self.responseSerializer copyWithZone:zone];
    HTTPClient.securityPolicy = [self.securityPolicy copyWithZone:zone];
    return HTTPClient;
}
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3.總結

可以看出AFHTTPSessionManager這個類就是將我們平常最常用的HTTP請求進行了封裝，方便我們呼叫。

原始碼閱讀系列：AFNetworking

原始碼閱讀：AFNetworking（一）——從使用入手

原始碼閱讀：AFNetworking（二）——AFURLRequestSerialization

原始碼閱讀：AFNetworking（三）——AFURLResponseSerialization

原始碼閱讀：AFNetworking（四）——AFSecurityPolicy

原始碼閱讀：AFNetworking（五）——AFNetworkReachabilityManager

原始碼閱讀：AFNetworking（六）——AFURLSessionManager

原始碼閱讀：AFNetworking（七）——AFHTTPSessionManager

原始碼閱讀：AFNetworking（八）——AFAutoPurgingImageCache

原始碼閱讀：AFNetworking（九）——AFImageDownloader

原始碼閱讀：AFNetworking（十）——AFNetworkActivityIndicatorManager

原始碼閱讀：AFNetworking（十一）——UIActivityIndicatorView+AFNetworking

原始碼閱讀：AFNetworking（十二）——UIButton+AFNetworking

原始碼閱讀：AFNetworking（十三）——UIImageView+AFNetworking

原始碼閱讀：AFNetworking（十四）——UIProgressView+AFNetworking

原始碼閱讀：AFNetworking（十五）——UIRefreshControl+AFNetworking

原始碼閱讀：AFNetworking（十六）——UIWebView+AFNetworking