0. 前言
iOS的开发中的网络下载方式包括NSData(最原始,实际开发基本不会用),NSURLConnection(古老又过气的苹果原生网络框架),NSURLSession(现在流行的苹果网络框架),AFNetworking,SDWebImage以及基于AFNetworking的二次封装框架例如XMNetworking,HYBNetworking等等。
NSURLConnection作为过气的框架,作为对比了解一下还是有必要的。NSURLSession作为众多网络相关的第三方框架基于的苹果原生框架,更是有必要学习总结一下。作为第三方框架,AFNetworking,SDWebImage等等其实它们的老版本是基于NSURLConnection封装而成的,后来才改成的基于NSURLSession。这些第三方框架相比原生框架封装了缓存的逻辑,比如内存缓存,磁盘缓存,操作缓存等等。
0.1 最原始的网络下载 -- NSData+NSURL方式
关键步骤
NSString-->NSURL-->NSData-->UIImage
关键API
URLWithString
dataWithContentsOfURL:url
imageWithData:data
下载示例
/** * 点击按钮 -- 使用NSData下载图片文件,并显示再imageView上 */ - (IBAction)downloadBtnClick:(UIButton *)sender { // 在子线程中发送下载文件请求 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // 创建下载路径 NSURL *url = [NSURL URLWithString:@"https://upload-images.jianshu.io/upload_images/1877784-b4777f945878a0b9.jpg"]; // NSData的dataWithContentsOfURL:方法下载 NSData *data = [NSData dataWithContentsOfURL:url]; // 回到主线程,刷新UI dispatch_async(dispatch_get_main_queue(), ^{ self.imageView.image = [UIImage imageWithData:data]; }); }); }
1. 过气的苹果原生网络框架 -- NSURLConnection
① 下载完的事件采用block形式的API
//handler A block which receives the results of the resource load. + (void)sendAsynchronousRequest:(NSURLRequest*) request queue:(NSOperationQueue*) queue completionHandler:(void (^)(NSURLResponse* _Nullable response, NSData* _Nullable data, NSError* _Nullable connectionError)) handler API_DEPRECATED("Use [NSURLSession dataTaskWithRequest:completionHandler:] (see NSURLSession.h", macos(10.7,10.11), ios(5.0,9.0), tvos(9.0,9.0)) __WATCHOS_PROHIBITED;
② 下载完的事件采用delegate形式的API
/* Designated initializer */ - (nullable instancetype)initWithRequest:(NSURLRequest *)request delegate:(nullable id)delegate startImmediately:(BOOL)startImmediately API_DEPRECATED("Use NSURLSession (see NSURLSession.h)", macos(10.5,10.11), ios(2.0,9.0), tvos(9.0,9.0)) __WATCHOS_PROHIBITED; - (nullable instancetype)initWithRequest:(NSURLRequest *)request delegate:(nullable id)delegate API_DEPRECATED("Use NSURLSession (see NSURLSession.h)", macos(10.3,10.11), ios(2.0,9.0), tvos(9.0,9.0)) __WATCHOS_PROHIBITED; + (nullable NSURLConnection*)connectionWithRequest:(NSURLRequest *)request delegate:(nullable id)delegate API_DEPRECATED("Use NSURLSession (see NSURLSession.h)", macos(10.3,10.11), ios(2.0,9.0), tvos(9.0,9.0)) __WATCHOS_PROHIBITED;
调用示例 -- 采用block的API ①
/** * 点击按钮 -- 使用NSURLConnection下载图片文件,并显示再imageView上 */ - (IBAction)downloadBtnClicked:(UIButton *)sender { // 创建下载路径 NSURL *url = [NSURL URLWithString:@"https://upload-images.jianshu.io/upload_images/1877784-b4777f945878a0b9.jpg"]; // NSURLConnection发送异步Get请求,该方法iOS9.0之后就废除了,推荐NSURLSession [NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:url] queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) { self.imageView.image = [UIImage imageWithData:data]; // 可以在这里把下载的文件保存 }]; }
调用示例 -- 采用delegate的API ②
- (IBAction)downloadBtnClicked:(UIButton *)sender { // 创建下载路径 NSURL *url = [NSURL URLWithString:@"http://dldir1.qq.com/qqfile/QQforMac/QQ_V5.4.0.dmg"]; // NSURLConnection发送异步Get请求,并实现相应的代理方法,该方法iOS9.0之后废除了。 [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:url] delegate:self]; }
代理实现方法示例
#pragma mark 实现方法 /** * 接收到响应的时候:创建一个空的沙盒文件 */ - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { // 获得下载文件的总长度 self.fileLength = response.expectedContentLength; // 沙盒文件路径 NSString *path = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"QQ_V5.4.0.dmg"]; NSLog(@"File downloaded to: %@",path); // 创建一个空的文件到沙盒中 [[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil]; // 创建文件句柄 self.fileHandle = [NSFileHandle fileHandleForWritingAtPath:path]; } /** * 接收到具体数据:把数据写入沙盒文件中 */ - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { // 指定数据的写入位置 -- 文件内容的最后面 [self.fileHandle seekToEndOfFile]; // 向沙盒写入数据 [self.fileHandle writeData:data]; // 拼接文件总长度 self.currentLength += data.length; // 下载进度 self.progressView.progress = 1.0 * self.currentLength / self.fileLength; self.progressLabel.text = [NSString stringWithFormat:@"当前下载进度:%.2f%%",100.0 * self.currentLength / self.fileLength]; } /** * 下载完文件之后调用:关闭文件、清空长度 */ - (void)connectionDidFinishLoading:(NSURLConnection *)connection { // 关闭fileHandle [self.fileHandle closeFile]; self.fileHandle = nil; // 清空长度 self.currentLength = 0; self.fileLength = 0; }
2. 现在的苹果原生网络框架 -- NSURLSession
在iOS9.0之后,以前使用的NSURLConnection过期,苹果推荐使用NSURLSession来替换NSURLConnection完成网路请求相关操作。NSURLSession的使用非常简单,先根据会话对象创建一个请求Task,然后执行该Task即可。NSURLSessionTask本身是一个抽象类,在使用的时候,通常是根据具体的需求使用它的几个子类。关系如下:
2.1 GET请求(NSURLRequest默认设置)
使用NSURLSession发送GET请求的方法和NSURLConnection类似,整个过程如下:
1)确定请求路径(一般由公司的后台开发人员以接口文档的方式提供),GET请求参数直接跟在URL后面
2)创建请求对象(默认包含了请求头和请求方法【GET】),此步骤可以省略
3)创建会话对象(NSURLSession)
4)根据会话对象创建请求任务(NSURLSessionDataTask)
5)执行Task
6)当得到服务器返回的响应后,解析数据(XML|JSON|HTTP)
① 下载完的事件采用block形式
get请求示例1
关键API
sharedSession
requestWithURL:
dataTaskWithRequest:
-(void)getWithBlock1 { //对请求路径的说明 //http://120.25.226.186:32812/login?username=520it&pwd=520&type=JSON //协议头+主机地址+接口名称+?+参数1&参数2&参数3 //协议头(http://)+主机地址(120.25.226.186:32812)+接口名称(login)+?+参数1(username=520it)&参数2(pwd=520)&参数3(type=JSON) //GET请求,直接把请求参数跟在URL的后面以?隔开,多个参数之间以&符号拼接 //1.确定请求路径 NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/login?username=520it&pwd=520it&type=JSON"]; //2.创建请求对象 //请求对象内部默认已经包含了请求头和请求方法(GET) NSURLRequest *request = [NSURLRequest requestWithURL:url]; //3.获得会话对象 NSURLSession *session = [NSURLSession sharedSession]; //4.根据会话对象创建一个Task(发送请求) /* 第一个参数:请求对象 第二个参数:completionHandler回调(请求完成【成功|失败】的回调) data:响应体信息(期望的数据) response:响应头信息,主要是对服务器端的描述 error:错误信息,如果请求失败,则error有值 */ NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) { if (error == nil) { //6.解析服务器返回的数据 //说明:(此处返回的数据是JSON格式的,因此使用NSJSONSerialization进行反序列化处理) NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil]; NSLog(@"%@",dict); } }]; //5.执行任务 [dataTask resume]; }
get请求示例2
关键API
sharedSession
dataTaskWithURL:
-(void)getWithBlock2 { //1.确定请求路径 NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/login?username=520it&pwd=520it&type=JSON"]; //2.获得会话对象 NSURLSession *session = [NSURLSession sharedSession]; //3.根据会话对象创建一个Task(发送请求) /* 第一个参数:请求路径 第二个参数:completionHandler回调(请求完成【成功|失败】的回调) data:响应体信息(期望的数据) response:响应头信息,主要是对服务器端的描述 error:错误信息,如果请求失败,则error有值 注意: 1)该方法内部会自动将请求路径包装成一个请求对象,该请求对象默认包含了请求头信息和请求方法(GET) 2)如果要发送的是POST请求,则不能使用该方法 */ NSURLSessionDataTask *dataTask = [session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) { //5.解析数据 NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil]; NSLog(@"%@",dict); }]; //4.执行任务 [dataTask resume]; }
② 下载完的事件采用delegate形式
关键API
requestWithURL:
sessionWithConfiguration
dataTaskWithRequest:request
get请求发起示例
-(void) getWithDelegate1 { //1.确定请求路径 NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/login?username=520it&pwd=520it&type=JSON"]; //2.创建请求对象 //请求对象内部默认已经包含了请求头和请求方法(GET) NSURLRequest *request = [NSURLRequest requestWithURL:url]; //3.获得会话对象,并设置代理 /* 第一个参数:会话对象的配置信息defaultSessionConfiguration 表示默认配置 第二个参数:谁成为代理,此处为控制器本身即self 第三个参数:队列,该队列决定代理方法在哪个线程中调用,可以传主队列|非主队列 [NSOperationQueue mainQueue] 主队列: 代理方法在主线程中调用 [[NSOperationQueue alloc]init] 非主队列: 代理方法在子线程中调用 */ NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]]; //4.根据会话对象创建一个Task(发送请求) NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request]; //5.执行任务 [dataTask resume]; }
代理关键API
//1.接收到服务器响应的时候调用该方法 -(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler { //2.接收到服务器返回数据的时候会调用该方法,如果数据较大那么该方法可能会调用多次 -(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data { //3.当请求完成(成功|失败)的时候会调用该方法,如果请求失败,则error有值 -(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
代理实现示例
#pragma mark NSURLSessionDataDelegate //1.接收到服务器响应的时候调用该方法 -(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler { //在该方法中可以得到响应头信息,即response NSLog(@"didReceiveResponse--%@",[NSThread currentThread]); //注意:需要使用completionHandler回调告诉系统应该如何处理服务器返回的数据 //默认是取消的 /* NSURLSessionResponseCancel = 0, 默认的处理方式,取消 NSURLSessionResponseAllow = 1, 接收服务器返回的数据 NSURLSessionResponseBecomeDownload = 2,变成一个下载请求 NSURLSessionResponseBecomeStream 变成一个流 */ completionHandler(NSURLSessionResponseAllow); } //2.接收到服务器返回数据的时候会调用该方法,如果数据较大那么该方法可能会调用多次 -(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data { NSLog(@"didReceiveData--%@",[NSThread currentThread]); //拼接服务器返回的数据 [self.responseData appendData:data]; } //3.当请求完成(成功|失败)的时候会调用该方法,如果请求失败,则error有值 -(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error { NSLog(@"didCompleteWithError--%@",[NSThread currentThread]); if(error == nil) { //解析数据,JSON解析请参考http://www.cnblogs.com/wendingding/p/3815303.html NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:self.responseData options:kNilOptions error:nil]; NSLog(@"%@",dict); } }
如下图所示,get请求内部封装了开始操作(其实是继续),不用再像NSURLSession一样外面resume了。
2.2 POST请求(需另外单独设置request.HTTPMethod属性)
post请求示例
关键API
sharedSession
requestWithURL:
request.HTTPMethod = @"POST";
dataTaskWithRequest:request completionHandler:
-(void)postWithBlock { //对请求路径的说明 //http://120.25.226.186:32812/login //协议头+主机地址+接口名称 //协议头(http://)+主机地址(120.25.226.186:32812)+接口名称(login) //POST请求需要修改请求方法为POST,并把参数转换为二进制数据设置为请求体 //1.创建会话对象 NSURLSession *session = [NSURLSession sharedSession]; //2.根据会话对象创建task NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/login"]; //3.创建可变的请求对象 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; //4.修改请求方法为POST request.HTTPMethod = @"POST"; //5.设置请求体 request.HTTPBody = [@"username=520it&pwd=520it&type=JSON" dataUsingEncoding:NSUTF8StringEncoding]; //6.根据会话对象创建一个Task(发送请求) /* 第一个参数:请求对象 第二个参数:completionHandler回调(请求完成【成功|失败】的回调) data:响应体信息(期望的数据) response:响应头信息,主要是对服务器端的描述 error:错误信息,如果请求失败,则error有值 */ NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) { //8.解析数据 NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil]; NSLog(@"%@",dict); }]; //7.执行任务 [dataTask resume]; }
3. HTTPS与HTTP的不同点
前面涉及到的GET和POST都属于HTTP请求,现在苹果的APP都推荐支持HTTPS,这就需要先配置一下证书,然后在NSURLSession(或者NSURLConnection但现在新的项目基本不用了)的代理方法里面进行一些特别的操作。如果是AFNetWorking,也需要对AFHTTPRequestOperationManager对象进行一些特别的操作。
关于证书的配置,及需要的特别的操作,推荐阅读:
4. AF封装了GET和POST操作的 -- AFHTTPSessionManager
AFNetworking2.0和3.0区别很大,也是因为苹果废弃了NSURLConnection,而改用了NSURLSession,AFNetworking3.0实际上只是对NSURLSession所做的操作进行了高度封装,提供更加简洁的API供编码调用。
查看AFHTTPSessionManager.h文件,可知AFHTTPSessionManager是AFURLSessionManager的子类:
@interface AFHTTPSessionManager : AFURLSessionManager
请求示例 -- 下载一个PDF文件
- (void)DownloadPdfAndSave{ AFHTTPSessionManager *manager = [AFHTTPSessionManager manager]; manager.responseSerializer = [AFHTTPResponseSerializer serializer]; manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"application/pdf"]; __weak __typeof__(self) weakSelf = self; //临时配置,需要自己根据接口地址改动!!!!!!!!!!!!!!!!!!!! self.urlStr = @"http://10.20.201.78/test3.pdf"; [manager GET:_urlStr parameters:nil progress:^(NSProgress * _Nonnull downloadProgress) { } success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) { __strong __typeof__(weakSelf) strongSelf = weakSelf; strongSelf.isWriten = [responseObject writeToFile:[self pathOfPdf] atomically:YES]; [strongSelf openPdfByAddingSubView]; //[strongSelf.previewController reloadData]; } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) { NSLog(@"%@",error.userInfo); }]; }
get请求调用栈分析
AFHTTPSessionManager.m
- (NSURLSessionDataTask *)GET:(NSString *)URLString parameters:(id)parameters success:(void (^)(NSURLSessionDataTask *task, id responseObject))success failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure { 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 { NSURLSessionDataTask *dataTask = [self dataTaskWithHTTPMethod:@"GET" URLString:URLString parameters:parameters uploadProgress:nil downloadProgress:downloadProgress success:success failure:failure]; [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 { NSError *serializationError = nil; NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:method URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters error:&serializationError]; if (serializationError) { if (failure) { dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{ failure(nil, serializationError); }); } return nil; } __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; }
AFURLSessionManager.m
- (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; url_session_manager_create_task_safely(^{ dataTask = [self.session dataTaskWithRequest:request]; }); [self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler]; return dataTask; }
5. AF的GET和POST请求实现第二层 -- AFURLSessionManager
5.1 downloadTaskWithRequest: progress: destination: completionandler:
AFURLSessionManager.m
调用示例
DownloadVC.m
- (IBAction)downloadBtnClicked:(UIButton *)sender { NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration]; // 1. 创建会话管理者 AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration]; // 2. 创建下载路径和请求对象 NSURL *URL = [NSURL URLWithString:@"http://dldir1.qq.com/qqfile/QQforMac/QQ_V5.4.0.dmg"]; NSURLRequest *request = [NSURLRequest requestWithURL:URL]; // 3.创建下载任务 /** * 第一个参数 - request:请求对象 * 第二个参数 - progress:下载进度block * 其中: downloadProgress.completedUnitCount:已经完成的大小 * downloadProgress.totalUnitCount:文件的总大小 * 第三个参数 - destination:自动完成文件剪切操作 * 其中: 返回值:该文件应该被剪切到哪里 * targetPath:临时路径 tmp NSURL * response:响应头 * 第四个参数 - completionHandler:下载完成回调 * 其中: filePath:真实路径 == 第三个参数的返回值 * error:错误信息 */ NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:^(NSProgress *downloadProgress) { __weak typeof(self) weakSelf = self; // 获取主线程,不然无法正确显示进度。 NSOperationQueue* mainQueue = [NSOperationQueue mainQueue]; [mainQueue addOperationWithBlock:^{ // 下载进度 weakSelf.progressView.progress = 1.0 * downloadProgress.completedUnitCount / downloadProgress.totalUnitCount; weakSelf.progressLabel.text = [NSString stringWithFormat:@"当前下载进度:%.2f%%",100.0 * downloadProgress.completedUnitCount / downloadProgress.totalUnitCount]; }]; } destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) { NSURL *path = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil]; return [path URLByAppendingPathComponent:@"QQ_V5.4.0.dmg"]; } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) { NSLog(@"File downloaded to: %@", filePath); }]; // 4. 开启下载任务 [downloadTask resume]; }
内部封装分析
AFURLSessionManager.m
- (NSURLSessionDownloadTask *)downloadTaskWithRequest:(NSURLRequest *)request progress:(void (^)(NSProgress *downloadProgress)) downloadProgressBlock destination:(NSURL * (^)(NSURL *targetPath, NSURLResponse *response))destination completionHandler:(void (^)(NSURLResponse *response, NSURL *filePath, NSError *error))completionHandler { __block NSURLSessionDownloadTask *downloadTask = nil; url_session_manager_create_task_safely(^{ downloadTask = [self.session downloadTaskWithRequest:request]; }); [self addDelegateForDownloadTask:downloadTask progress:downloadProgressBlock destination:destination completionHandler:completionHandler]; return downloadTask; }
其中self.session是AFURLSessionManager.h中的属性
@property (readonly, nonatomic, strong) NSURLSession *session;
它后面调用的API声明在NSFoundation的NSURLSession.h的头文件中
/* Creates a data task with the given request. The request may have a body stream. */ - (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request;
添加代理的封装
AFURLSessionManager.m
- (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; }
其中
- (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]; }
其中,self.mutableTaskDelegatesKeyedByTaskIdentifier是个字典
@property (readwrite, nonatomic, strong) NSMutableDictionary *mutableTaskDelegatesKeyedByTaskIdentifier;
被调用的地方在:
- (AFURLSessionManagerTaskDelegate *)delegateForTask:(NSURLSessionTask *)task { NSParameterAssert(task); AFURLSessionManagerTaskDelegate *delegate = nil; [self.lock lock]; delegate = self.mutableTaskDelegatesKeyedByTaskIdentifier[@(task.taskIdentifier)]; [self.lock unlock]; return delegate; }
进而被调用的地方在:
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location { AFURLSessionManagerTaskDelegate *delegate = [self delegateForTask:downloadTask]; if (self.downloadTaskDidFinishDownloading) { NSURL *fileURL = self.downloadTaskDidFinishDownloading(session, downloadTask, location); if (fileURL) { delegate.downloadFileURL = fileURL; NSError *error = nil; [[NSFileManager defaultManager] moveItemAtURL:location toURL:fileURL error:&error]; if (error) { [[NSNotificationCenter defaultCenter] postNotificationName:AFURLSessionDownloadTaskDidFailToMoveFileNotification object:downloadTask userInfo:error.userInfo]; } return; } } if (delegate) { [delegate URLSession:session downloadTask:downloadTask didFinishDownloadingToURL:location]; } }
5.2 dataTaskWithRequest: completionHandler:
说明:这个NSURLSession的API容易跟AFURLSessionManager的API混淆,参数都是一个request和一个handler block。
NSURLSession的API是这样的:
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error))completionHandler {
而AFURLSessionManager的API是这样的,可以对比学习下:
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler {
调用示例 -- dataTaskWithRequest:
DownloadVC.m
// 创建下载URL NSURL *url = [NSURL URLWithString:@"http://dldir1.qq.com/qqfile/QQforMac/QQ_V5.4.0.dmg"]; // 2.创建request请求 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; // 设置HTTP请求头中的Range NSString *range = [NSString stringWithFormat:@"bytes=%zd-", self.currentLength]; [request setValue:range forHTTPHeaderField:@"Range"]; __weak typeof(self) weakSelf = self; _downloadTask = [self.manager dataTaskWithRequest:request completionHandler:^(NSURLResponse * _Nonnull response, id _Nullable responseObject, NSError * _Nullable error) { NSLog(@"dataTaskWithRequest"); // 清空长度 weakSelf.currentLength = 0; weakSelf.fileLength = 0; // 关闭fileHandle [weakSelf.fileHandle closeFile]; weakSelf.fileHandle = nil; }];
其中self.manager是懒加载得到的AFURLSessionManager
/** * manager的懒加载 */ - (AFURLSessionManager *)manager { if (!_manager) { NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration]; // 1. 创建会话管理者 _manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration]; } return _manager; }
内部封装分析
AFURLSessionManager.m
- (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSURLResponse *response, id responseObject, NSError *error))completionHandler { return [self dataTaskWithRequest:request uploadProgress:nil downloadProgress:nil completionHandler:completionHandler]; }
- (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; url_session_manager_create_task_safely(^{ dataTask = [self.session dataTaskWithRequest:request]; }); [self addDelegateForDataTask:dataTask uploadProgress:uploadProgressBlock downloadProgress:downloadProgressBlock completionHandler:completionHandler]; return dataTask; }
6. 调用栈分析
初始化AFHTTPSessionManager的内部实现调用栈
[AFHTTPSessionManager initWithBaseURL:]
[AFHTTPSessionManager initWithBaseURL:sessionConfiguration:]
[AFURLSessionManager initWithSessionConfiguration:] // 调用了父类AFURLSessionManager的初始化方法
[NSURLSession sessionWithConfiguration:delegate:delegateQueue:] // 调用了原生类NSURLSession的初始化方法
[AFJSONResponseSerializer serializer]
[AFSecurityPolicy defaultPolicy]
[AFNetworkReachabilityManager sharedManager]
[AFHTTPRequestSerializer serializer]
[AFJSONResponseSerializer serializer]
AFHTTPSessionManager发送请求的内部实现调用栈
[AFHTTPSessionManager GET:parameters:process:success:failure:]
[AFHTTPSessionManager dataTaskWithHTTPMethod:parameters:uploadProgress:downloadProgress:success:failure:] // 【注解1】
[AFHTTPRequestSerializer requestWithMethod:URLString:parameters:error:] // 获得NSMutableURLRequest
[AFURLSessionManager dataTaskWithRequest:uploadProgress:downloadProgress:completionHandler:] // 【注解2】
[NSURLSession dataTaskWithRequest:] // 【注解3】
[AFURLSessionManager addDelegateForDataTask:uploadProgress:downloadProgress:completionHandler:] // 添加代理
[AFURLSessionManagerTaskDelegate init]
[AFURLSessionManager setDelegate:forTask:]
[NSURLSessionDataTask resume]
其中,【注解1】、【注解2】、【注解3】这三个方法得到的是同一个对象,即【注解3】中系统原生的NSURLSessionDataTask对象。所以,AF请求操作内部实现也是和原生NSURLSession操作一样,创建task,调用resume发送请求。
7. 开放问题:session与TCP连接数
请求的时候,NSURLSession的session跟TCP的个数是否有什么关系?有人说请求同域名且共享的session会复用同一个TCP链接,否则就不复用,就一个session一个TCP连接?
关于这块的知识可研究资料较少,且不可信,笔者日后研究到确定的答案后再更新。也欢迎读者留下自己的见解。
不过据我观察,可能没那么简单,新的iOS11系统新增了多路TCP即Multipath-TCP,因而也为NSURLSession和NSURLSessionConfiguration提供了新的属性multipathServiceType,以及HTTPMaximumConnectionsPerHost。下面是它们的定义:
NSURLSession.h
/* multipath service type to use for connections. The default is NSURLSessionMultipathServiceTypeNone */ @property NSURLSessionMultipathServiceType multipathServiceType API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(macos, watchos, tvos); /* The maximum number of simultanous persistent connections per host */ @property NSInteger HTTPMaximumConnectionsPerHost;
NSURLSession.h
typedef NS_ENUM(NSInteger, NSURLSessionMultipathServiceType) { NSURLSessionMultipathServiceTypeNone = 0, /* None - no multipath (default) */ NSURLSessionMultipathServiceTypeHandover = 1, /* Handover - secondary flows brought up when primary flow is not performing adequately. */ NSURLSessionMultipathServiceTypeInteractive = 2, /* Interactive - secondary flows created more aggressively. */ NSURLSessionMultipathServiceTypeAggregate = 3 /* Aggregate - multiple subflows used for greater bandwitdh. */ } API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(macos, watchos, tvos) NS_SWIFT_NAME(URLSessionConfiguration.MultipathServiceType);
NSURLSessionConfiguration.h
/* multipath service type to use for connections. The default is NSURLSessionMultipathServiceTypeNone */ @property NSURLSessionMultipathServiceType multipathServiceType API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(macos, watchos, tvos); /* The maximum number of simultanous persistent connections per host */ @property NSInteger HTTPMaximumConnectionsPerHost;
作者:陈满iOS
链接:https://www.jianshu.com/p/dee6a7ec8393