开源中国iOS客户端学习——网络通信AFNetworking类库

AFNetworking是一个轻量级的iOS网络通信类库，继ASI类库不在更新之后开发者们有一套不错选择；

AFNetworking类库源码下载和使用教程: https://github.com/AFNetworking/AFNetworking

如果想深入研究有官方文档介绍:http://afnetworking.github.com/AFNetworking/

在开源中国iOS客户端中关于AFNetworking类库的使用只用到了两个实例方法

(1)getPath:parameters:success:failure:

(2)postPath:parameters:success:failure:

他们用法基本相同，只是请求数据方式不同，一种是Get请求和Post请求。Get是向服务器发索取数据的一种请求，也就相当于查询信息功能，不会修改类容，Post是向服务器提交数据的一种请求，影响数据内容；两种方法定义：

 - (void)getPath:(NSString *)path
      parameters:(NSDictionary *)parameters
         success:(void (^)(AFHTTPRequestOperation *operation, id responseObject))success
         failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failure
 {
     NSURLRequest *request = [self requestWithMethod:@"GET" path:path parameters:parameters];
     AFHTTPRequestOperation *operation = [self HTTPRequestOperationWithRequest:request success:success failure:failure];
     [self enqueueHTTPRequestOperation:operation];
 }

 - (void)postPath:(NSString *)path
       parameters:(NSDictionary *)parameters
          success:(void (^)(AFHTTPRequestOperation *operation, id responseObject))success
          failure:(void (^)(AFHTTPRequestOperation *operation, NSError *error))failure
 {
     NSURLRequest *request = [self requestWithMethod:@"POST" path:path parameters:parameters];
     AFHTTPRequestOperation *operation = [self HTTPRequestOperationWithRequest:request success:success failure:failure];
     [self enqueueHTTPRequestOperation:operation];
 }

getPath:parameters:success:failure:方法在程序中使用举例:

NewsView.m

 - (void)reload:(BOOL)noRefresh
 {
     //如果有网络连接
     if ([Config Instance].isNetworkRunning) {
         if (isLoading || isLoadOver) {
             return;
         }
         if (!noRefresh) {
             allCount = 0;
         }
         int pageIndex = allCount/20;
         NSString *url;

         switch (self.catalog) {
             case 1:
                 url = [NSString stringWithFormat:@"%@?catalog=%d&pageIndex=%d&pageSize=%d", api_news_list, 1, pageIndex, 20];
                 break;
             case 2:
                 url = [NSString stringWithFormat:@"%@?type=latest&pageIndex=%d&pageSize=%d", api_blog_list, pageIndex, 20];
                 break;
             case 3:
                 url = [NSString stringWithFormat:@"%@?type=recommend&pageIndex=%d&pageSize=%d", api_blog_list, pageIndex, 20];
                 break;
         }

         [[AFOSCClient sharedClient]getPath:url parameters:Nil

           success:^(AFHTTPRequestOperation *operation, id responseObject) {

             [Tool getOSCNotice2:operation.responseString];
             isLoading = NO;
             if (!noRefresh) {
                 [self clear];
             }

             @try {
                 NSMutableArray *newNews = self.catalog <= 1 ?

                 [Tool readStrNewsArray:operation.responseString andOld: news]:
                 [Tool readStrUserBlogsArray:operation.responseString andOld: news];
                 int count = [Tool isListOver2:operation.responseString];
                 allCount += count;
                 if (count < 20)
                 {
                     isLoadOver = YES;
                 }
                 [news addObjectsFromArray:newNews];
                 [self.tableNews reloadData];
                 [self doneLoadingTableViewData];

                 //如果是第一页 则缓存下来
                 if (news.count <= 20) {
                     [Tool saveCache:5 andID:self.catalog andString:operation.responseString];
                 }
             }
             @catch (NSException *exception) {
                 [NdUncaughtExceptionHandler TakeException:exception];
             }
             @finally {
                 [self doneLoadingTableViewData];
             }
         } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
             NSLog(@"新闻列表获取出错");
             //如果是刷新
             [self doneLoadingTableViewData];

             if ([Config Instance].isNetworkRunning == NO) {
                 return;
             }
             isLoading = NO;
             if ([Config Instance].isNetworkRunning) {
                 [Tool ToastNotification:@"错误 网络无连接" andView:self.view andLoading:NO andIsBottom:NO];
             }
         }];
         isLoading = YES;
         [self.tableNews reloadData];
     }
     //如果没有网络连接
     else
     {
         NSString *value = [Tool getCache:5 andID:self.catalog];
         if (value) {
             NSMutableArray *newNews = [Tool readStrNewsArray:value andOld:news];
             [self.tableNews reloadData];
             isLoadOver = YES;
             [news addObjectsFromArray:newNews];
             [self.tableNews reloadData];
             [self doneLoadingTableViewData];
         }
     }
 }

分析一下这里面的代码：

首先是做一个网络连接判断，在开源中国iOS客户端学习——(六)网络连接检测一文中介绍了，作者并不是用这种方法来判断，而是使用getPath:parameters:success:failure:来判断网络的连接，方法使用AFHTTPRequestOperation和“PATCH”请求HTTP客户端操作队列，使用到了block块(iOS 4.0+特性)，URL请求成功执行success块里操作，这里面block块没有返回值，接受两个参数，创建请求操作和响应数据请求，URL请求失败执行failure里面的方法，这个block块里仍没有返回值，接受两个参数创建请求操作和NSError对象，描述网络或解析错误状况；

在 if()中的方法[Config Instance].isNetworkRunning==YES的,如果程序加载或者已经加载完毕什么也不返回，如果程序没有加载数据，将数据列表数量显示为0，接下来是在switch()中，根据使用者选择设置不同API接口(下图)，然后就是解析显示数据信息，显示在视图中；

  

在AFNetwork 文件夹中，作者自己添加了一个AFOSCClient类，该类继承AFHTTPClient，又设计了一个sharedClient的类方法，从返回的结果可以推测出它是通过API请求返回json类型的数据，具体什么作用还没看出来；

[Tool getOSCNotice2:operation.responseString];是封装在在Tool类中的解析获取的XML的文件

URL请求成功，还做了一个程序异常处理，防止请求数据过成功程序异常崩溃

 关于@try @catch @finally异常处理的使用：

@try 
{ 
//执行的代码，其中可能有异常。一旦发现异常，则立即跳到catch执行。否则不会执行catch里面的内容 
} 
@catch 
{ 
//除非try里面执行代码发生了异常，否则这里的代码不会执行 
} 
@finally 
{ 
//不管什么情况都会执行，包括try catch 里面用了return ,可以理解为只要执行了try或者catch，就一定会执行 finally
} 

如果URL请求的数据出错，则反应网络不连通，数据不能加载，则弹出GCDiscreetNotificationView提示视图  提示网络错误；

postPath:parameters:success:failure:方法在程序中使用举例:

FriendsView.m

 -(void)reload:(BOOL)noRefresh
 {
     if (isLoadOver) {
         [self doneLoadingTableViewData];
         return;
     }

     [[AFOSCClient sharedClient] postPath:api_friends_list
             parameters:[NSDictionary dictionaryWithObjectsAndKeys:segement.selectedSegmentIndex == 0 ? @"1" : @"0",@"relation",
                         [NSString stringWithFormat:@"%d", friends.count/20],@"pageIndex",
                         @"20",@"pageSize",
                         [NSString stringWithFormat:@"%d", [Config Instance].getUID],@"uid",nil] success:^(AFHTTPRequestOperation *operation, id responseObject) {

                 if (!noRefresh) {
                     [self clear];
                 }

                 [self doneLoadingTableViewData];
                 isLoading = NO;
                 NSString *response = operation.responseString;
                 [Tool getOSCNotice2:response];
                 @try {

                     TBXML *xml = [[TBXML alloc] initWithXMLString:response error:nil];
                     TBXMLElement *root = xml.rootXMLElement;
                     //显示
                     TBXMLElement *_friends = [TBXML childElementNamed:@"friends" parentElement:root];
                     if (!_friends) {
                         isLoadOver = YES;
                         [self.tableFriends reloadData];
                         return;
                     }
                     TBXMLElement *first = [TBXML childElementNamed:@"friend" parentElement:_friends];
                     if (first == nil) {
                         [self.tableFriends reloadData];
                         isLoadOver = YES;
                         return;
                     }
                     NSMutableArray *newFriends = [[NSMutableArray alloc] initWithCapacity:20];
                     TBXMLElement *name = [TBXML childElementNamed:@"name" parentElement:first];
                     TBXMLElement *userid = [TBXML childElementNamed:@"userid" parentElement:first];
                     TBXMLElement *portrait = [TBXML childElementNamed:@"portrait" parentElement:first];
                     TBXMLElement *expertise = [TBXML childElementNamed:@"expertise" parentElement:first];
                     TBXMLElement *gender = [TBXML childElementNamed:@"gender" parentElement:first];
                     Friend *f = [[Friend alloc] initWithParameters:[TBXML textForElement:name] andUID:[[TBXML textForElement:userid] intValue] andPortrait:[TBXML textForElement:portrait] andExpertise:[TBXML textForElement:expertise] andMale:[[TBXML textForElement:gender] intValue] == 1];
                     if (![Tool isRepeatFriend: friends andFriend:f]) {
                         [newFriends addObject:f];
                     }
                     while (first) {
                         first = [TBXML nextSiblingNamed:@"friend" searchFromElement:first];
                         if (first) {
                             name = [TBXML childElementNamed:@"name" parentElement:first];
                             userid = [TBXML childElementNamed:@"userid" parentElement:first];
                             portrait = [TBXML childElementNamed:@"portrait" parentElement:first];
                             expertise = [TBXML childElementNamed:@"expertise" parentElement:first];
                             gender = [TBXML childElementNamed:@"gender" parentElement:first];
                             f = [[Friend alloc] initWithParameters:[TBXML textForElement:name] andUID:[[TBXML textForElement:userid] intValue] andPortrait:[TBXML textForElement:portrait] andExpertise:[TBXML textForElement:expertise] andMale:[[TBXML textForElement:gender] intValue] == 1];
                             if (![Tool isRepeatFriend:friends andFriend:f]) {
                                 [newFriends addObject:f];
                             }
                         }
                         else
                             break;
                     }
                     if (newFriends.count < 20) {
                         isLoadOver = YES;
                     }

                     [friends addObjectsFromArray:newFriends];
                     [self.tableFriends reloadData];

                 }
                 @catch (NSException *exception) {
                     [NdUncaughtExceptionHandler TakeException:exception];
                 }
                 @finally {
                     [self doneLoadingTableViewData];
                 }

             } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

                 NSLog(@"好友列表获取出错");

                 [self doneLoadingTableViewData];
                 isLoading = NO;
                 if ([Config Instance].isNetworkRunning) {
                     [Tool ToastNotification:@"错误 网络无连接" andView:self.view andLoading:NO andIsBottom:NO];
                 }

             }];

     isLoading = YES;
     [self.tableFriends reloadData];
 }

这个方法和getPath:parameters:success:failure:不同的在于请求方式是POST请求，可以向服务器里提交数据；