iphone - 未转义控制字符的间歇性 JSON 解析器失败

Question

在 iPhone 应用程序中搜索 Twitter 某些文本的功能。代码非常简单，我将 url 字符串传递给 twitter api，然后解析结果。尽管有一半时间 JSON 解析器因未转义控制字符“0x0”而出错。下面的代码和完整的错误消息。

    - (void)grabData:(NSString *)searchTerm {
     NSString *urlString = [NSString stringWithFormat:@"http://search.twitter.com/search.json?q=%@&rpp=25",searchTerm];

     NSURL *url = [NSURL URLWithString:urlString];

     NSLog(@"Created url:%@",url);

     //Setup and start async download
     NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
     NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
     [connection release];
     [request release];
    }

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

     // Store incoming data into a string
     NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

     //NSLog(@"Did receive some data %@",jsonString);

     //Create a dictionary from the JSON string
     NSDictionary *results = [jsonString JSONValue];

     // Build an Array from the dictionary for easy access to each entry
     NSDictionary *tweets = [results objectForKey:@"results"];

            // Loop through each entry in the dictionary
    for(NSDictionary *tweet in tweets) {
     // Get the user string for the tweet
     NSString *tUser = [tweet objectForKey:@"from_user"];
           NSLog(@"Tweet from %@",tUser);
          }

    }

来自控制台的错误消息，50% 的时间，其他 50% 的时间按预期工作。

2010-12-20 21:22:02.022 TwitterSearch[47362:207] Created url:http://search.twitter.com/search.json?q=red&rpp=25
2010-12-20 21:22:02.361 TwitterSearch[47362:207] -JSONValue failed. Error trace is: (
    "Error Domain=org.brautaset.JSON.ErrorDomain Code=5 \"Unescaped control character '0x0'\" UserInfo=0x4d6a130 {NSLocalizedDescription=Unescaped control character '0x0'}",
    "Error Domain=org.brautaset.JSON.ErrorDomain Code=3 \"Object value expected for key: profile_image_url\" UserInfo=0x4d6a200 {NSUnderlyingError=0x4d6a170 \"Unescaped control character '0x0'\", NSLocalizedDescription=Object value expected for key: profile_image_url}",
    "Error Domain=org.brautaset.JSON.ErrorDomain Code=3 \"Expected value while parsing array\" UserInfo=0x4d6a240 {NSUnderlyingError=0x4d6a1e0 \"Object value expected for key: profile_image_url\", NSLocalizedDescription=Expected value while parsing array}",
    "Error Domain=org.brautaset.JSON.ErrorDomain Code=3 \"Object value expected for key: results\" UserInfo=0x4d6a310 {NSUnderlyingError=0x4d6a2d0 \"Expected value while parsing array\", NSLocalizedDescription=Object value expected for key: results}"
)

Answer 1

didReceiveData 方法可以在数据传送时被多次调用。所以在那个方法中，你应该简单地将每个传入的 block 附加到一个 NSMutableData 类变量(而不是处理它)。

完整数据的处理应该在connectionDidFinishLoading方法中完成。

错误的发生可能是因为它正在尝试解析部分数据 block 。