这里对网络请求方式做一个总结。
原生方式同步GET请求：
1 NSString *urlStr = @"http://apis.juhe.cn/mobile/get?phone=13429667914&key=e87a054855796995c9e2b48e8514d0da";2 urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];3 NSURL *url = [NSURL URLWithString:urlStr];4 NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];5 NSURLResponse *response = nil;6 NSError *error = nil;7 NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];8 NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];9 NSLog(@"%@", responseString);
原生方式异步GET请求：
1 NSString *urlStr = @"http://apis.juhe.cn/mobile/get?phone=13429667914&key=e87a054855796995c9e2b48e8514d0da";2 urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];3 NSURL *url = [NSURL URLWithString:urlStr];4 NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];5 [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {6 NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];7 NSLog(@"%@", responseString);8 }]; 可见，请求分为两部分，一是构建请求，二是发送请求。构建分为GET和POST，发送分为同步和异步。
POST请求的请求部分需要将参数构建为NSData类型：
1 NSString *urlStr = @"http://apis.juhe.cn/mobile/get?"; 2 urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding]; 3 NSURL *url = [NSURL URLWithString:urlStr]; 4 5 //创建请求，配置参数的data 6 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:30]; 7 [request setHTTPMethod:@"POST"]; 8 NSString *otherURLstr = @"phone=13429667914&key=e87a054855796995c9e2b48e8514d0da"; 9 NSData *otherURLData = [otherURLstr dataUsingEncoding:NSUTF8StringEncoding];10 [request setHTTPBody:otherURLData];
原生方式写出来的代码总是一坨，下面看看AFN对请求的封装。AFN需要添加MobileCoreService和SystemConfiguration框架，并在pch里加入头文件：
1 #import2 #import
在使用时需要引入头文件：
1 #import "AFNetworking.h"
GET和POST的请求的构建还是和前面一样，发送处：
1 AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];2 [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {3 NSLog(@"%@", operation.responseString);4 } failure:^(AFHTTPRequestOperation *operation, NSError *error) {5 NSLog(@"%@", [error localizedDescription]);6 }];7 [operation start]; AFHTTPRequestOperation是操作队列的子类，显然AFN的请求是异步的（当然，既然是操作队列，就可以用操作队列的方法控制它），请求完成后触发回调。
AFN支持自动解析JSON并转化为词典结构：
1 AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {2 NSLog(@"%@", JSON);3 } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {4 }];5 [operation start]; 但是个人不建议使用它解析XML，因为它采用的是XMLParser的方式，很繁琐。
但是这还是显得一坨一坨的，于是有两种办法，第一种就是再封装一层简单的API，就像jQueryAjax一样，第二种就是每次用的时候复制粘贴啦~
使用AFN也可以很方便地实现文件异步下载：
1 //目标地址 2 NSURL *url = [NSURL URLWithString:@"http://www.baidu.com/img/baidu_sylogo1.gif"]; 3 NSURLRequest *request = [NSURLRequest requestWithURL:url]; 4 5 //构建AFN操作 6 AFURLConnectionOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request]; 7 8 //设置输出流 9 NSArray *documents = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);10 NSString *downloadPath = [documents[0] stringByAppendingPathComponent:@"1.gif"];11 [operation setOutputStream:[NSOutputStream outputStreamToFileAtPath:downloadPath append:NO]];12 13 //下载过程当中的block（检测进度）14 [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {15 NSLog(@"下载百分比：%f", (float)totalBytesRead / totalBytesExpectedToRead);16 }];17 18 //下载完成19 [operation setCompletionBlock:^{20 NSLog(@"操作完成");21 }];