AFNetWorking能做什么

AFNetwork是一个轻量级的网络请求api类库。是以NSURLConnection, NSOperation和其它方法为基础的。
 
以下这个样例是用来处理json请求的：
NSURL *url = [NSURL URLWithString:@"https://alpha-api.app.net/stream/0/posts/stream/global"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
    NSLog(@"App.net Global Stream: %@", JSON);
} failure:nil];
[operation start];
用法：
1.下载AFNetwork， 点击下载
2.将目录名称为AFNetworking拖入到你的工程项目就可以
常见问题：
1.  AFNetworking作用都有哪些？
NSURLConnection 提供了+sendAsynchronousRequest:queue:completionHandler: 和+sendAsynchronousRequest:queue:completionHandler: ，可是AFNetworking提供了更好的功能
＊AFURLConnectionOperation和它的子类继承NSOperation的，同意请求被取消，暂停/恢复和由NSOperationQueue进行管理。
 
＊AFURLConnectionOperation也能够让你轻松得完毕上传和下载，处理验证。监控上传和下载进度，控制的缓存。
 
＊AFHTTPRequestOperation和它得子类能够基于http状态和 内容列下来区分是否成功请求了
＊AFNetworking能够将远程媒体数据类型（NSData）转化为可用的格式。比方如JSON，XML，图像和plist。
 
＊AFHTTPClient提供了一个方便的网络交互接口，包含默认头，身份验证。是否连接到网络，批量处理操作。查询字符串參数序列化。已经多种表单请求
＊的UIImageView+ AFNetworking添加了一个方便的方法来异步载入图像。
2. AFNetworking是否支持缓存？
能够。NSURLCache及其子类提供了非常多高级接口用于处理缓存
假设你想将缓存存储再磁盘，推荐使用SDURLCache
3.怎样使用AFNetworking上传一个文件？
NSData *imageData = UIImagePNGRepresentation(image);
NSURLRequest *request = [client multipartFormRequestWithMethod:@"POST" path:@"/upload" parameters:nil constructingBodyWithBlock: ^(id <AFMultipartFormData> formData) {
  [formData appendPartWithFileData:imageData mimeType:@"image/png" name:@"avatar"];
}];
4.怎样使用AFNetworking下载一个文件？
先创建一个 AFURLConnectionOperation对象，然后再使用它的属性 outputStream进行处理
operation.outputStream = [NSOutputStream outputStreamToFileAtPath:@"download.zip" append:NO];
5.怎样解决：SystemConfiguration framework not found in project
请导入：
#import <SystemConfiguration/SystemConfiguration.h>
#import <MobileCoreServices/MobileCoreServices.h>
6.当应用程序退出时。怎样保持持续的请求？
AFURLConnectionOperation有一个叫 setShouldExecuteAsBackgroundTaskWithExpirationHandler:的方法用于处理在应用程序进入后台后，进行持续的请求
[self setShouldExecuteAsBackgroundTaskWithExpirationHandler:^{
}];
一些实例：
1.XML 请求
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://api.flickr.com/services/rest/?method=flickr.groups.browse&api_key=b6300e17ad3c506e706cb0072175d047&cat_id=34427469792%40N01&format=rest"]];
AFXMLRequestOperation *operation = [AFXMLRequestOperation XMLParserRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, NSXMLParser *XMLParser) {
  XMLParser.delegate = self;
  [XMLParser parse];
} failure:nil];
[operation start];
2.图片请求：
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 100.0f, 100.0f)];
[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]];
3.图片上传处理，监測上传状态：
didiwei  17:28:57
NSURL *url = [NSURL URLWithString:@"http://api-base-url.com"];
AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
NSData *imageData = UIImageJPEGRepresentation([UIImage imageNamed:@"avatar.jpg"], 0.5);
NSMutableURLRequest *request = [httpClient multipartFormRequestWithMethod:@"POST" path:@"/upload" parameters:nil constructingBodyWithBlock: ^(id <AFMultipartFormData>formData) {
    [formData appendPartWithFileData:imageData name:@"avatar" fileName:@"avatar.jpg" mimeType:@"image/jpeg"];
}];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[operation setUploadProgressBlock:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {
    NSLog(@"Sent %lld of %lld bytes", totalBytesWritten, totalBytesExpectedToWrite);
}];
[operation start];
4.在线流媒体请求
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://localhost:8080/encode"]];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
operation.inputStream = [NSInputStream inputStreamWithFileAtPath:[[NSBundle mainBundle] pathForResource:@"large-image" ofType:@"tiff"]];
operation.outputStream = [NSOutputStream outputStreamToMemory];
[operation start];