原生网络请求以及AFN网络请求/异步下载

这里对网络请求方式做一个总结。

原生方式同步GET请求：

     NSString *urlStr = @"http://apis.juhe.cn/mobile/get?phone=13429667914&key=e87a054855796995c9e2b48e8514d0da";
     urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
     NSURL *url = [NSURL URLWithString:urlStr];
     NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:];
     NSURLResponse *response = nil;
     NSError *error = nil;
     NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
     NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
     NSLog(@"%@", responseString);

原生方式异步GET请求：

     NSString *urlStr = @"http://apis.juhe.cn/mobile/get?phone=13429667914&key=e87a054855796995c9e2b48e8514d0da";
     urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
     NSURL *url = [NSURL URLWithString:urlStr];
     NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:];
     [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
         NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
         NSLog(@"%@", responseString);
     }];

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：

     NSString *urlStr = @"http://apis.juhe.cn/mobile/get?";
     urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
     NSURL *url = [NSURL URLWithString:urlStr];
    
     //创建请求，配置参数的data
     NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:];
     [request setHTTPMethod:@"POST"];
     NSString *otherURLstr = @"phone=13429667914&key=e87a054855796995c9e2b48e8514d0da";
     NSData *otherURLData = [otherURLstr dataUsingEncoding:NSUTF8StringEncoding];
     [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：

     #import <MobileCoreServices/MobileCoreServices.h>
     #import <SystemConfiguration/SystemConfiguration.h>

在使用时需要引入头文件：

 #import "AFNetworking.h"

GET和POST的请求的构建还是和前面一样，发送处：

     AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
     [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
         NSLog(@"%@", operation.responseString);
     } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
         NSLog(@"%@", [error localizedDescription]);
     }];
     [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：

     AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
         NSLog(@"%@", JSON);
     } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
     }];
     [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：

     //目标地址
     NSURL *url = [NSURL URLWithString:@"http://www.baidu.com/img/baidu_sylogo1.gif"];
     NSURLRequest *request = [NSURLRequest requestWithURL:url];

     //构建AFN操作
     AFURLConnectionOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];

     //设置输出流
     NSArray *documents = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
     NSString *downloadPath = [documents[] stringByAppendingPathComponent:@"1.gif"];
     [operation setOutputStream:[NSOutputStream outputStreamToFileAtPath:downloadPath append:NO]];

     //下载过程当中的block（检测进度）
     [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {
         NSLog(@"下载百分比：%f", (float)totalBytesRead / totalBytesExpectedToRead);
     }];

     //下载完成
     [operation setCompletionBlock:^{
         NSLog(@"操作完成");
     }];