NSJSONSerialization 不工作，NSUTF8StringEncoding 工作

Question

我已经阅读了文档、教程和其他 Stack Q&A，我很想知道如何使用 NSUTF8StringEncoding 让我的 JSON 出现，但不使用 NSJSONSerialization - 这就是我需要将数据提取到NSDictionary 或NSArray。我认为这是从我的 URL 返回的 NSData 格式的问题？

编辑这里是错误：Error Domain=NSCocoaErrorDomain Code=3840“无法完成操作。（Cocoa 错误 3840。）”（垃圾结束。） UserInfo=0x8aabc30

NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.sampleURL.com"]
                                          cachePolicy:NSURLRequestUseProtocolCachePolicy
                                      timeoutInterval:15.0];

NSMutableData* responseData = [NSMutableData dataWithCapacity: 0];

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

    //this works, and have NSLog below
    responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"string %@", responseString);

    [responseData appendData:data];
    responseData = [[NSMutableData alloc] initWithData:data];

     //this is null in NSLog
    NSError * error;
    NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:data   options:NSJSONReadingMutableContainers|NSJSONReadingAllowFragments error:&error];

    NSLog(@"jsonDict dict %@",jsonDict); 
}

调试控制台：

 2014-03-11 07:41:58.233 WBPC[7845:a0b] string   {"id":"a1","session":"General","name":"Exhibitor Setup Begins","startTime":"0900","details":"9am Exhibitor Hall","png":"image","speaker1":"Johnson","speaker2":"Nelson","speaker3":""}{"id":"b1","session":"General","name":"Conference Registration","startTime":"1000","details":"10am Noon Upper Level Lobby","png":"image","speaker1":"Jackson","speaker2":"","speaker3":""}
 2014-03-11 07:41:58.236 WBPC[7845:a0b] jsonDict (null)

Answer 1

您在 'didReceiveData' 委托函数中完成这一切，这不是正确的位置。唯一应该存在的是：

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [self.responseData appendData:data];
}

但在此之前，您应该在连接收到响应时初始化“self.responseData”：

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if(self.responseData != nil) self.responseData = nil;
    self.responseData = [[NSMutableData alloc] init];
}

然后，您需要实现另一个名为“connectionDidFinishLoading”的委托函数，当调用此方法时，您的“responseData”将包含来自 JSON 的所有数据并准备好解析：

-(void)connectionDidFinishLoading:(NSURLConnection *)connection {

     responseString = [[NSString alloc] initWithData:self.responseData encoding:NSUTF8StringEncoding];

     NSLog(@"string %@", responseString);

     NSError * error;
     NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers|NSJSONReadingAllowFragments error:&error];

     NSLog(@"jsonDict dict %@",jsonDict); 
}

我希望这在某种程度上有所帮助。

Answer 2

您的 JSON 格式不正确。您告诉我们它是（为便于阅读而添加了空格和换行符）：

{
    "id": "a1",
    "session": "General",
    "name": "Exhibitor Setup Begins",
    "startTime": "0900",
    "details": "9am Exhibitor Hall",
    "png": "image",
    "speaker1": "Johnson",
    "speaker2": "Nelson",
    "speaker3": ""
}{
    "id": "b1",
    "session": "General",
    "name": "Conference Registration",
    "startTime": "1000",
    "details": "10am Noon Upper Level Lobby",
    "png": "image",
    "speaker1": "Jackson",
    "speaker2": "",
    "speaker3": ""
}

这在两个字典条目之间缺少逗号，并且您缺少应该包装 JSON 的 [ 和 ]。如果它真的是一个字典条目数组，它应该是：

[
    {
        "id": "a1",
        "session": "General",
        "name": "Exhibitor Setup Begins",
        "startTime": "0900",
        "details": "9am Exhibitor Hall",
        "png": "image",
        "speaker1": "Johnson",
        "speaker2": "Nelson",
        "speaker3": ""
    },
    {
        "id": "b1",
        "session": "General",
        "name": "Conference Registration",
        "startTime": "1000",
        "details": "10am Noon Upper Level Lobby",
        "png": "image",
        "speaker1": "Jackson",
        "speaker2": "",
        "speaker3": ""
    }
]

如果你想检查你的 JSON，你可以访问http://jsonlint.com。此外，如果您检查了 JSONObjectWithData 返回的 error 对象，它会为您指明正确的方向。

您应该看看这个 JSON 是如何生成的。看起来它必须是手动生成的。例如，如果您从 PHP 页面生成此文件，则应使用 json_encode，而不是手动生成 JSON。

---

顺便说一句，您正在尝试解析didReceiveData 中的结果。在connectionDidFinishLoading 之前，您不应该尝试解析。您的 didReceiveData 应该仅将 data 附加到您的 NSMutableData 对象。解析应该推迟到connectionDidFinishLoading。

Answer 3

你好，你可以试试这个。

NSError *error = nil;
NSArray *jsonResponseArray = [NSJSONSerialization JSONObjectWithData: YOURDATA options: NSJSONReadingMutableContainers error: &error];

if (!jsonResponseArray) {
  NSLog(@"Error: %@", error);
} else {
   for(NSDictionary *dic in jsonResponseArray) {
      NSLog(@"dic values are : %@", item);
   }
}

谢谢

Answer 4

您发布的 JSON 字符串不是有效的 JSON。仅仅因为数据是有效的 UTF8 字符串并不意味着它一定是 JSON。尝试将调试后的字符串粘贴到 JSONLint 中，它会显示您的 JSON 对象之间缺少逗号。