how to extract value of an element from JSON data using RegEx

Question

I am trying to extract value of "points" element from JSON data using

    NSString* encodedPoints = [apiResponse stringByMatching:@"points:\\\"([^\\\"]*)\\\"" capture:1L];

but there are more than one "points" elements in the JSON data. Plz help me i dont know much about regular expressions. i am getting JSON Data from this link

i am not sure if you can use mapkit to display directions , as it is against the legal clause of google. please confirm it from someone. — Ankit Srivastava
– Ankit Srivastava, Commented Dec 9, 2011 at 12:00
But thats what we are doing using there Directions api. right?? — Virat Naithani
– Virat Naithani, Commented Dec 9, 2011 at 12:14

zaph · Accepted Answer · 2011-12-09 12:35:34Z

1

You should use a JSON scanner.

Ensure that you have the JSON in an NSString, not an NSData.

Here is a method that uses an NSScanner instead of a regular expression:

NSMutableArray *pointList = [NSMutableArray array];
NSString *pointsString;
BOOL success = YES;
NSScanner *scanner = [NSScanner scannerWithString:encodedPoints];

while (YES) {
    success = [scanner scanUpToString:@"points:\"" intoString:nil];
    success = [scanner scanString:@"points:\"" intoString:nil];
    if (success == NO)
        break;
    success = [scanner scanUpToString:@"\"" intoString:&pointsString];
    [pointList addObject:pointsString];
}

// Show results by print lengths of the found points
for (NSString *point in pointList)
    NSLog(@"point length: %i", point.length);

NSLog output:

point length: 22058
point length: 8889

answered Dec 9, 2011 at 12:35

zaph

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Comments

Aditya Kumar Pandey · Accepted Answer · 2011-12-09 12:20:45Z

0

You should use a JSON parser for this as that would be more correct/idea for dealing with JSON than using a regex which is prone to failure.

answered Dec 9, 2011 at 12:20

Aditya Kumar Pandey

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8 Comments

Virat Naithani Over a year ago

JSON parsers are not working because it is giving invalid JSON response

Virat Naithani Over a year ago

stackoverflow.com/questions/8444697/…

Aditya Kumar Pandey Over a year ago

It depends on which JSON parser you are using and where it fails. To my old eyes, the JSON looked good.

Aditya Kumar Pandey Over a year ago

I saw the other thread. It seems that they are not generating JSON to consume as JSON but instead for setting some variables in Javascript. You could just use the following to make it proper JSON.

Aditya Kumar Pandey Over a year ago

jsonlint.com let me knew what was wrong. A couple of regexs would fix it. The first problem is with keys in a JSON object. It can be fixed by (\w\+)(\:)/"\1"\2/cg regular expression. The second problem is first value which is not escaping certain characters. Apart from that, JSON is correct.

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