iOS 解析 JSON 时出错

Question

我是 iOS 新手。我有需要解析的 JSON 数据：

{  
   "allseries":[  
      {  
         "type":"HR",
         "title":"Heart Rate",
         "xLabel":"Time",
         "yLabel":"Beats per Min",
         "defaultUnit":"BPM",
         "url":"info/info?user=admin%40korrent.com&type=HR",
         "size":18,
         "firstTs":1406755651,
         "lastTs":1406841254
      },
      {  
         "type":"TEMP",
         "title":"Temperature",
         "xLabel":"Time",
         "yLabel":"Temperature",
         "defaultUnit":"F",
         "url":"info/info?user=admin%40korrent.com&type=TEMP",
         "size":6,
         "firstTs":1406854147,
         "lastTs":1406854283
      }
   ],
   "status":"OK"
}

到目前为止，这是我的代码：

NSString *dataReceived= [[NSString alloc] initWithData:_responseData encoding:NSUTF8StringEncoding];
NSLog(@"--> async response data (string): %@", dataReceived);
NSData *jsonData = [dataReceived dataUsingEncoding:NSUTF8StringEncoding];
NSError *jsonError;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:nil error:&jsonError];
NSLog(@"JSON key and value %@", [dict description]);
NSLog(@" %@ ", dict[@"allseries"]);
NSString *jsonString=dict[@"allseries"];
   if (_programState == 4){
    NSLog(@"state is 4");
    NSLog(@"%@",jsonString);
    NSData *Data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

但是，代码为这一行抛出了无效参数异常：

 NSData *Data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];

此外，jsonString 似乎完全“无法操作”。我无法拆分它，将字符串附加到它等等。那么有什么问题？

Answer 1

// The following two lines are just for logging and otherwise are not needed.
NSString *dataReceived= [[NSString alloc] initWithData:_responseData encoding:NSUTF8StringEncoding];
NSLog(@"--> async response data (string): %@", dataReceived);

// Deserialize the JSON data into a dictionary
NSError *jsonError;
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData: _responseData options:nil error:&jsonError];
NSLog(@"JSON key and value %@", dict);

// Get the array from the dictionary element "allseries".
NSArray *jsonArray = dict[@"allseries"];
NSLog(@"jsonArray: %@", jsonArray);

这里 jsonArray 是 JSON 中“allseries”的字典数组

Answer 2

你所做的完全，完全错误。

dict[@allseries] 不是 NSString。它是一个有两个元素的 NSArray，它的两个元素都是 NSDictionary。