iOS网络开发——JSON数据解码(使用NSJSONSerialization)

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下面我们通过一个案例MyNotes学习一下NSJSONSerialization的用法。这里重新设计数据结构为JSON格式，

其中备忘录信息Notes.json文件的内容如下：

{"ResultCode":0,"Record":[{"ID":"1","CDate":"2012-12-23","Content":"发布iOSBook0","UserID":"tony"},{"ID":"2","CDate":"2012-12-24","Content":"发布iOSBook1","UserID":"tony"},{"ID":"3","CDate":"2012-12-25","Content":"发布iOSBook2","UserID":"tony"},{"ID":"4","CDate":"2012-12-26","Content":"发布iOSBook3","UserID":"tony"},{"ID":"5","CDate":"2012-12-27","Content":"发布iOSBook4","UserID":"tony"}]}

事实上，NSJSONSerialization使用起来更为简单，只要能确定你的项目使用了iOS 5 SDK就可以了。修改视图
控制器MasterViewController的viewDidLoad方法，具体代码如下：

- (void)viewDidLoad{[super viewDidLoad];self.navigationItem.leftBarButtonItem = self.editButtonItem;self.detailViewController = (DetailViewController *)[[self.splitViewController.viewControllers lastObject] topViewController];[[NSNotificationCenter defaultCenter] addObserver:self  selector:@selector(reloadView:)  name:@"reloadViewNotification"  object:nil];//路径,实际开发中要请求服务器端NSString* path = [[NSBundle mainBundle] pathForResource:@"Notes" ofType:@"json"];NSData *jsonData = [[NSData alloc] initWithContentsOfFile:path];NSError *error;//options参数指定了解下JSON的模式://NSJSONReadingMutableContainers -指定解析返回的是可变的数组或字典.(这个常量是合适的选择)//NSJSONReadingMutableLeaves。指定叶节点是可变字符串。//NSJSONReadingAllowFragments。指定顶级节点可以不是数组或字典id jsonObj = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error];if (!jsonObj || error) {NSLog(@"JSON解码失败");}self.listData = [jsonObj objectForKey:@"Record"];}

此外，NSJSONSerialization还提供了JSON编码的方法：dataWithJSONObject:options:error:和
writeJSONObject:toStream:options:error:。

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