iOS JSON Parse not working (returns null dictionary)

问题

I use the NSJSONSerialization's JSONObjectWithData:data options: error: to parse JSON data returned from a server.

Now for the options parameter I use: NSJSONReadingAllowFragments. You can look below and see the actual JSON (where I believe the problem is).

The error message I get is:

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (Invalid value around character 0.) UserInfo=0x6895da0 {NSDebugDescription=Invalid value around character 0.}

Any idea how to fix it?

JSON =

{"name":"Johan Appleseed",
"email":"j.appleseed@emuze.co",
"phone":"+4121876003",
"accounts":{
    "facebook":[true,1125],
    "twitter":[false,null],
    "homepage":[true,"http:\/\/johnAplleseed.com\/index.html"]}}

回答1:

Probably you have some unprintable character that you cannot see. Try this:

NSData *jsonData = ...
const unsigned char *ptr = [data bytes];

for(int i=0; i<[data length]; ++i) {
  unsigned char c = *ptr++;
  NSLog(@"char=%c hex=%x", c, c);
}

To verify you don't have unprintable characters at the beginning or end of the data.

EDIT: to clarify, just run the above on your JSON dictionary - the one that fails to parse.

回答2:

Ive acctualy discovered the problem to be the fact that the return from the URL is an HTML page, ant there all these html, head, and body tags around the actual response, so it can't be parsed. This is a good Q&A on how to remove the HTML tags from the response (after it has been changed into a string) : Remove HTML Tags from an NSString on the iPhone

回答3:

I had the same problem for a while, I just figured out that if I'm pulling data from a webpage let's say PHP page, there should not be any HTML tags in that page. So a structure like:

<html>
<body>
<?php

?>
</body>
</html>

will ruin your result. turning it into:

<?php

?>

worked for me.

回答4:

It's been a while but an easier way of printing the data is:

NSLog(@"%@", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);

回答5:

One way is there , you can parse jsondata by post request

 -(void)callWebserviceList
 {
spinner.hidden=NO;

NSString *bodyData = @"code_request=monuments_list&asi_id=1";

NSMutableURLRequest *postRequest = [NSMutableURLRequest requestWithURL:[NSURL   URLWithString:@"http://asicircles.com/server_sync.php"]];

// Set the request's content type to application/x-www-form-urlencoded
[postRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

// Designate the request a POST request and specify its body data
[postRequest setHTTPMethod:@"POST"];
[postRequest setHTTPBody:[NSData dataWithBytes:[bodyData UTF8String] length:strlen([bodyData UTF8String])]];

connection1 = [NSURLConnection connectionWithRequest:postRequest delegate:self];

if(connection1 !=nil)
{
    ////NSLog(@"%@",postRequest);
}

}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

if ([connection isEqual:connection1 ])
{
     [responseData setLength:0];

}else if ([connection isEqual:connection2 ])
{
     [responseData1 setLength:0];
}

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

    if ([connection isEqual:connection1 ])
  {
    [responseData appendData:data];

}else if ([connection isEqual:connection2 ])
{
     [responseData1 appendData:data];
}


//**check here for responseData & also data**

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(@"%@",[NSString stringWithFormat:@"Connection failed: %@", [error description]]);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if ([connection isEqual:connection1 ])
{
    spinner.hidden=YES;
    NSError *error;

    NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

    NSMutableArray *arrdata=[json objectForKey:@"message"];
    NSLog(@"code is%@", json);

    for (int i=0; i< arrdata.count; i++)
    {
        [arrDetails addObject:[[arrdata objectAtIndex:i]objectForKey:@"details"]];
        [arrImageUrl addObject:[[arrdata objectAtIndex:i]objectForKey:@"image"]];
        [arrLat addObject:[[arrdata objectAtIndex:i]objectForKey:@"lat"]];
        [arrLongi addObject:[[arrdata objectAtIndex:i]objectForKey:@"longi"]];
        [arrName addObject:[[arrdata objectAtIndex:i]objectForKey:@"name"]];
        [arrLoc addObject:[[arrdata objectAtIndex:i]objectForKey:@"location"]];
        [arrID addObject:[[arrdata objectAtIndex:i]objectForKey:@"id"]];

        NSLog(@"code is%@",[[arrdata objectAtIndex:i]objectForKey:@"details"]);
        NSLog(@"code is%@",[arrImageUrl objectAtIndex:i]);

    }



    if (arrName.count > 0)
    {
        [self addscrollView];
    }



}else if ([connection isEqual:connection2 ])
{

}


}

回答6:

You can also hit url for json data by block in ios

 #define kBgQueue dispatch_get_global_queue(
 DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) //1
#define kLatestKivaLoansURL [NSURL URLWithString: 
 @"http://api.kivaws.org/v1/loans/search.json?status=fundraising"] //2

The first thing we need to do is download the JSON data from the web. Luckily, with GCD we can do this in one line of code! Add the following to ViewController.m:

- (void)viewDidLoad
{
[super viewDidLoad];

dispatch_async(kBgQueue, ^{
    NSData* data = [NSData dataWithContentsOfURL: 
      kLatestKivaLoansURL];
    [self performSelectorOnMainThread:@selector(fetchedData:) 
      withObject:data waitUntilDone:YES];
});
}
- (void)fetchedData:(NSData *)responseData {
//parse out the json data
NSError* error;
NSDictionary* json = [NSJSONSerialization 
    JSONObjectWithData:responseData //1

    options:kNilOptions 
    error:&error];

NSArray* latestLoans = [json objectForKey:@"loans"]; //2

NSLog(@"loans: %@", latestLoans); //3
}

来源：https://stackoverflow.com/questions/12071207/ios-json-parse-not-working-returns-null-dictionary

标签

ios

json

parsing

nsjsonserialization