iOS_AFNetworking 结构解析+用例分析+源码阅读

// 1. 创建configuration(配置)
// NSURLSessionConfiguration 有3个工厂方法
// default: 共享 NSHTTPCookieStorage, NSURLCache, NSURLCredentialStorage
// ephemeral: 不会存储 缓存、Cookie、证书, 适用于秘密浏览
// backgroundWithID: 可以在程序 挂起、退出、崩溃 的情况下, 上传和下载任务, ID用于向任何可能在进程外恢复后台传输的守护进程（daemon）提供上下文
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
// 2. 创建sessionManager
  // 2.1.创建网络请求回调queue
  // 2.2.创建安全策略
  // 2.3.初始化: 代理字典{task-delegate}、锁(访问代理字典的)
  // 2.4.遍历session中所有的task: 数据task、上传task、下载task
    // 2.4.1 为每个task创建taskDelegate, 并将代理都存入字典中
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
// 3. 根据URL创建request
NSURL *URL = [NSURL URLWithString:@"http://example.com/download.zip"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
// 4. 创建downloadTask
  // 4.1 运用NSURLSession, 根据request创建downloadTask (系统方法)
  // 4.2 为downloadTask添加taskDelegate
    // 4.2.1 根据downloadTask创建taskDelegate
    // 4.2.2 为taskDelegate设置: manager、competion回调
    // 4.2.3 为taskDelegate设置finish回调
    // 4.2.4 将taskDelegate存入字典中 (加锁)
      // 接收task的暂停和恢复通知 (通过替换系统的`resume`和`suspend`方法, 添加的notify实现)
    // 4.2.5 为taskDelegate设置: progress回调
NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request
                                                                 progress:nil
                                                              destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
  // 返回刚下载的文件路径
  NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory
                                                                        inDomain:NSUserDomainMask
                                                               appropriateForURL:nil
                                                                          create:NO
                                                                           error:nil];
  return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
  NSLog(@"File downloaded to: %@", filePath);
}];
// 5. 开始执行
[downloadTask resume];

// 1. 创建configuration(配置)
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
// 2. 创建sessionManager
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
// 3. 根据URL创建request
NSURL *URL = [NSURL URLWithString:@"http://example.com/upload"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
// 4. 获取需要上传文件的URL
NSString *imageFile = [[NSBundle mainBundle] pathForResource:@"photo" ofType:@"PNG"];
NSURL *filePath = [NSURL fileURLWithPath:imageFile];
// 5. 创建uploadTask
  // 5.1 运用NSURLSession根据request和fileURL创建uploadTask (系统方法)
  // 5.2 为uploadTask添加taskDelegate (详情同 downloadTask 4.2)
NSURLSessionUploadTask *uploadTask = [manager uploadTaskWithRequest:request
                                                           fromFile:filePath
                                                           progress:nil
                                                  completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
    if (error) {
      NSLog(@"Error: %@", error);
    } else {
      NSLog(@"Success: %@ %@", response, responseObject);
    }
}];
// 6. 开始执行
[uploadTask resume];

// 1. 根据method、URL、parameters、可变body block、error, 创建mutableRequest
  // 1.1 根据method、URL、parameters、error, 创建mutableRequest
  // 1.2 根据mutableRequest创建formData
  // 1.3 parameters -> [AFQueryStringPair], 并将其添加在formData后面, 有block则调用并传回formData
  // 1.4 设置request
    // 1.4.1 设置bodyStream的初始和结尾边界
    // 1.4.2 将bodyStream作为请求报文体
    // 1.4.3 设置请求头的Content-Type和Content-Length字段
NSMutableURLRequest *request = [[AFHTTPRequestSerializer serializer]
                                multipartFormRequestWithMethod:@"POST" // 不支持GET, HEAD类型
                                URLString:@"http://example.com/upload"
                                parameters:nil
                                constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
  // formData支持三种格式的数据: NSData, FileURL, NSInputStream
  NSString *imageFile = [[NSBundle mainBundle] pathForResource:@"beautiful" ofType:@"jpg"];
  [formData appendPartWithFileURL:[NSURL fileURLWithPath:imageFile]
                             name:@"file"
                         fileName:@"filename.jpg"
                         mimeType:@"image/jpeg"
                            error:nil];
} error:nil];
// 2. (同downloadTask的1-2)
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
// 3. 运用AFURLSessionManager根据request, 创建streamed uploadTask
  // 详情(同upload 5)
NSURLSessionUploadTask *uploadTask = [manager uploadTaskWithStreamedRequest:request progress:^(NSProgress * _Nonnull uploadProgress) {
  // 子线程回调, 更新UI需要dispatch到主线程
  dispatch_async(dispatch_get_main_queue(), ^{
    // refresh UI
  });
} completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
  if (error) {
    NSLog(@"Error: %@", error);
  } else {
    NSLog(@"%@ %@", response, responseObject);
  }
}];
// 4. 开始执行
[uploadTask resume];

// 1. (同downloadTask的1-2)
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
// 2. 根据URL创建request
NSURL *URL = [NSURL URLWithString:@"http://httpbin.org/get"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];
// 3. 运用AFURLSessionManager根据request, 创建dataTask
  // 3.1 运用NSURLSession根据request, 创建dataTask (系统方法)
  // 3.2 为dataTask添加taskDelegate (详情同 downloadTask 4.2)
NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request uploadProgress:nil downloadProgress:nil completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
  if (error) {
    NSLog(@"Error: %@", error);
  } else {
    NSLog(@"%@ %@", response, responseObject);
  }
}];
[dataTask resume];

dispatch_async(dispatch_get_main_queue(), ^{ //mo: 在主线程队列中异步执行
  // 发出notification
});

//mo: __Require_noErr_Quiet: 如果出错, 则跳转到 _out
/* 根据证书和政策创建一个信任管理对象
 certificates: 要认证的证书+你认为对证书有用的任何其他证书
 policies: 参考评估政策
 trust: 返回时, 指向新创建的信任管理对象
*/
__Require_noErr_Quiet(SecTrustCreateWithCertificates(allowedCertificate, policy, &allowedTrust), _out);
//mo: 忽略弃用警告
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
  //mo: 评估指定 证书 和 策略 的信任 (同步的)
  __Require_noErr_Quiet(SecTrustEvaluate(allowedTrust, &result), _out);
#pragma clang diagnostic pop
  //mo: 在`叶证书`求值后返回其公钥
  allowedPublicKey = (__bridge_transfer id)SecTrustCopyPublicKey(allowedTrust);
_out:

#pragma mark - mo: 代理字典存取
//mo: 字典的操作不是线程安全的, 所以用`NSLock`加锁
- (AFURLSessionManagerTaskDelegate *)delegateForTask:(NSURLSessionTask *)task {
  NSParameterAssert(task);
  AFURLSessionManagerTaskDelegate *delegate = nil;
  [self.lock lock]; //mo: 读取加锁
  delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)];
  [self.lock unlock];
  return delegate;
}
- (void)setDelegate:(AFURLSessionManagerTaskDelegate *)delegate forTask:(NSURLSessionTask *)task {
  NSParameterAssert(task);
  NSParameterAssert(delegate);
  [self.lock lock];  //mo: 写入加锁
  self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)] = delegate;
  [self addNotificationObserverForTask:task];
  [self.lock unlock];
}

//mo: 用`keyEnumerator`遍历keys, 此时不可更改字典 (还有个objectEnumerator可以遍历value)
for (NSString *headerField in headers.keyEnumerator) {
  [request setValue:headers[headerField] forHTTPHeaderField:headerField];
}

// 请求头修改队列：并行
self.requestHeaderModificationQueue = dispatch_queue_create("requestHeaderModificationQueue", DISPATCH_QUEUE_CONCURRENT);
#pragma mark - request headers 读写
// mo: 并行同步: 读 / 写(barrier: 保证队列之前的任务都执行完毕, 之后得等自己执行完毕)
- (void)setValue:(NSString *)value forHTTPHeaderField:(NSString *)field {
  dispatch_barrier_sync(self.requestHeaderModificationQueue, ^{
    [self.mutableHTTPRequestHeaders setValue:value forKey:field];
  });
}
- (NSString *)valueForHTTPHeaderField:(NSString *)field {
    NSString __block *value;
  dispatch_sync(self.requestHeaderModificationQueue, ^{
    value = [self.mutableHTTPRequestHeaders valueForKey:field];
  });
  return value;
}