无法访问Objective-C中的JSON数据

Question

Ok, this is my first approach to JSONs in Objective-C (and i'm quite new to the last one too). i'm to get infos stored my json to use them in Objective-C, but when trying to load it i get null in response from NSLog(@"%@",allData); on. Can anybody please tell me what i am doing wrong? thanks in advance for your time and your patience. oh and if needed here's the json: http://jsonviewer.stack.hu/#http://conqui.it/ricette.json

NSString *filePath = [[NSBundle mainBundle] pathForResource:@"recipes" ofType:@"json"];

NSError *error = nil;

NSMutableData *JSONData = [NSData dataWithContentsOfFile:filePath options:NSDataReadingMappedIfSafe error:&error];
NSLog(@"%@",JSONData);


NSArray *allData = [NSJSONSerialization JSONObjectWithData:JSONData options:0 error:nil];
NSLog(@"%@",allData);

for (NSDictionary *diction in allData) {
    NSString *recipe = [diction objectForKey:@"recipe"];

    [array addObject:recipe];
}

NSLog(@"%@",array);

Answer 1

The JSONObjectWithData method has an error parameter, of which you can avail yourself in order to diagnose the problem. For example:

NSError *error = nil;
NSArray *allData = [NSJSONSerialization JSONObjectWithData:JSONData
                                                   options:0
                                                     error:&error];
if (error)
    NSLog(@"%s: JSONObjectWithData error: %@", __FUNCTION__, error);

In your comments, you suggest that you received an error about "Unescaped control character around character 414." That would suggest an error in the JSON, itself, which you might want to validate by copying into http://jsonlint.com/ and see if it reports any issues.

In response to the broader question about whether there are any Objective-C issues, there are no coding errors, per se. I can't comment on the for loop which clearly assumes that allData is an array of dictionaries to which I cannot attest without seeing the JSON. But I'll take your word for it. But, yes, the Objective-C code looks fine (albeit, a little light on checking of the return values types and error objects).

For example, if you wanted some diagnostic assert statements that you could use during development, you might do something like:

NSArray *allData = [NSJSONSerialization JSONObjectWithData:JSONData options:0 error:nil];
NSAssert(error, @"%s: JSONObjectWithData error: %@", __FUNCTION__, error);

NSLog(@"%s: array=%@", __FUNCTION__, array);

NSAssert([allData isKindOfClass:[NSArray class]], @"allData is not an array");

for (NSDictionary *diction in allData) {
    NSAssert([diction isKindOfClass:[NSDictionary class]], @"%s: diction is not a dictionary (%@), __FUNCTION__, diction);

    NSString *recipe = [diction objectForKey:@"recipe"];

    NSAssert(recipe, @"%s: Did not find recipe key in diction (%@)", __FUNCTION__, diction);

    [array addObject:recipe];
}

If any of these errors were possible runtime errors in production, you'd replace assert statements with if statements that do the necessary error handling. But hopefully it illustrates the concept.

Answer 2

Problem in your response is that , string values are unable to concatenate.So, I have to manually remove those tabs and new lines.

At five places you are getting error ie:

pelate.

pasta.

pomodoro.

saporiti).

\\t

- (void)viewDidLoad
{
    NSString *urlStr=[NSString stringWithFormat:@"http://www.conqui.it/ricette.json"];

    urlStr=[urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *fileNameURL=[NSURL URLWithString:urlStr];

    NSLog(@"url is %@",urlStr);

    NSMutableURLRequest *filenameReq=[[NSMutableURLRequest alloc] initWithURL:fileNameURL];
    NSData *responseData=[NSURLConnection sendSynchronousRequest:filenameReq returningResponse:nil error:nil];

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

    responseString=[[responseString componentsSeparatedByString:@"\n"] componentsJoinedByString:@""];
    responseString=[responseString stringByReplacingOccurrencesOfString:@"\t" withString:@""];

    responseData=[responseString dataUsingEncoding:NSUTF8StringEncoding];

    NSLog(@"response String is %@",responseString);

    [NSCharacterSet characterSetWithCharactersInString:responseString];

    NSError *e = nil;
    NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData:responseData options: 0 error: &e];

    NSLog(@"JSON Array is %@ & error is %@",jsonArray,e);

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}