Core Foundation中NSURLConnection在2003年伴随着Safari浏览器的发行，诞生的时间比较久远，iOS升级比较快，AFNetWorking在3.0版本删除了所有基于NSURLConnection API的所有支持，新的API完全基于NSURLSession。AFNetworking 1.0建立在NSURLConnection的基础之上 ，AFNetworking 2.0使用NSURLConnection基础API，以及较新基于NSURLSession的API的选项。NSURLSession用于请求数据，作为URL加载系统，支持http，https，ftp，file，data协议。

基础知识

URL加载系统中需要用到的基础类:

iOS7和Mac OS X 10.9之后通过NSURLSession加载数据，调用起来也很方便： 

NSURL *url=[NSURL URLWithString:@"http://www.cnblogs.com/xiaofeixiang"];    NSURLRequest *urlRequest=[NSURLRequest requestWithURL:url];    NSURLSession *urlSession=[NSURLSession sharedSession];    NSURLSessionDataTask *dataTask=[urlSession dataTaskWithRequest:urlRequest completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {        NSDictionary *content = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];        NSLog(@"%@",content);    }];    [dataTask resume];

 

NSURLSessionTask是一个抽象子类，它有三个具体的子类是可以直接使用的：NSURLSessionDataTask，NSURLSessionUploadTask和NSURLSessionDownloadTask。这三个类封装了现代应用程序的三个基本网络任务：获取数据，比如JSON或XML，以及上传下载文件。dataTaskWithRequest方法用的比较多，关于下载文件代码完成之后会保存一个下载之后的临时路径:

NSURLSessionDownloadTask *downloadTask=[urlSession downloadTaskWithRequest:urlRequest completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {            }];

NSURLSessionUploadTask上传一个本地URL的NSData数据:

NSURLSessionUploadTask *uploadTask=[urlSession uploadTaskWithRequest:urlRequest fromData:[NSData new] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {            }];

NSURLSession在Foundation中我们默认使用的block进行异步的进行任务处理，当然我们也可以通过delegate的方式在委托方法中异步处理任务，关于委托常用的两种NSURLSessionTaskDelegate和NSURLSessionDownloadDelegate，其他的关于NSURLSession的委托有兴趣的可以看一下API文档，首先我们需要设置delegate:

NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];    NSURLSession *inProcessSession = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];    NSString *url = @"http://www.cnblogs.com/xiaofeixiang";    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];    NSURLSessionTask *dataTask = [inProcessSession dataTaskWithRequest:request];    [dataTask resume];

任务下载的设置delegate:

NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];    NSURLSession *inProcessSession = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];    NSString *url = @"http://www.cnblogs.com/xiaofeixiang";    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];    NSURLSessionDownloadTask *downloadTask = [inProcessSession downloadTaskWithRequest:request];    [downloadTask resume];

关于delegate中的方式只实现其中的两种作为参考:

#pragma mark - NSURLSessionDownloadDelegate-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location{    NSLog(@"NSURLSessionTaskDelegate--下载完成");}#pragma mark - NSURLSessionTaskDelegate-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error{     NSLog(@"NSURLSessionTaskDelegate--任务结束");}

NSURLSession状态同时对应着多个连接，不能使用共享的一个全局状态，会话是通过工厂方法来创建配置对象。

defaultSessionConfiguration(默认的，进程内会话)，ephemeralSessionConfiguration(短暂的，进程内会话)，backgroundSessionConfigurationWithIdentifier(后台会话)

第三种设置为后台会话的，当任务完成之后会调用application中的方法:

-(void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler{    }

网络封装

上面的基础知识能满足正常的开发，我们可以对常见的数据get请求，Url编码处理，动态添加参数进行封装,其中关于url中文字符串的处理

stringByAddingPercentEncodingWithAllowedCharacters属于新的方式，字符允许集合选择的是URLQueryAllowedCharacterSet，

NSCharacterSet中分类有很多，详细的可以根据需求进行过滤~

typedef void (^CompletioBlock)(NSDictionary *dict, NSURLResponse *response, NSError *error);@interface FENetWork : NSObject+(void)requesetWithUrl:(NSString *)url completeBlock:(CompletioBlock)block;+(void)requesetWithUrl:(NSString *)url params:(NSDictionary *)params completeBlock:(CompletioBlock)block;@end

 

@implementation FENetWork+(void)requesetWithUrl:(NSString *)url completeBlock:(CompletioBlock)block{    NSString *urlEnCode=[url stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];    NSURLRequest *urlRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:urlEnCode]];    NSURLSession *urlSession=[NSURLSession sharedSession];    NSURLSessionDataTask *dataTask=[urlSession dataTaskWithRequest:urlRequest completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {        if (error) {            NSLog(@"%@",error);            block(nil,response,error);        }else{            NSDictionary *content = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];            block(content,response,error);        }    }];    [dataTask resume];}+(void)requesetWithUrl:(NSString *)url params:(NSDictionary *)params completeBlock:(CompletioBlock)block{        NSMutableString *mutableUrl=[[NSMutableString alloc]initWithString:url];    if ([params allKeys]) {        [mutableUrl appendString:@"?"];        for (id key in params) {            NSString *value=[[params objectForKey:key] stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];            [mutableUrl appendString:[NSString stringWithFormat:@"%@=%@&",key,value]];        }    }    [self requesetWithUrl:[mutableUrl substringToIndex:mutableUrl.length-1] completeBlock:block];}@end

参考资料:https://developer.apple.com/library/prerelease/mac/documentation/Cocoa/Reference/Foundation/Classes/NSCharacterSet_Class/index.html#//apple_ref/occ/clm/NSCharacterSet/URLQueryAllowedCharacterSet

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