Getting part of an NSString

[chrishannah]

In my app i'm creating now i use goo.gl's url shortener api to shorted urls. I have it nearly working, I can send the longUrl to retrieve the short one in a NSString but it's in this format: { "kind": "urlshortener#url", "id": "http://goo.gl/something", "longUrl": "http://somethinglonggggg/" }

I just wondered if there is a way to just take the id (short url) from that.

Here's what I have so far:

NSString *longURL = urlText.text; NSData *reqData = [[NSString stringWithFormat:@"{\"longUrl\":\"%@\"}", longURL] dataUsingEncoding:NSUTF8StringEncoding];

NSMutableURLRequest *request = [NSMutableURLRequest
                                requestWithURL:[NSURL URLWithString:@"https://www.googleapis.com/urlshortener/v1/url"]
                                cachePolicy:NSURLRequestUseProtocolCachePolicy
                                timeoutInterval:20];
[request setHTTPMethod:@"POST"];
[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request setHTTPBody:reqData];

NSError *err = [[NSError alloc] init];
NSData *retData = [NSURLConnection sendSynchronousRequest:request
                                        returningResponse:nil
                                                    error:&err];

if([err domain]) return;

NSString *retString = [[NSString alloc] initWithData:retData encoding:NSUTF8StringEncoding];

if([retString rangeOfString:@"\"error\""].length) return;

NSLog(@" longUrl equals %@ ", longURL);
NSLog(@" retString equals %@ ", retString);

urlText.text = retString;

[dany_dev]

that format is JSON, my advice is not to parse it with normal methods but using a framework that can easily do it, like SBJson

[chrishannah]

Originally Posted by dany_dev

that format is JSON, my advice is not to parse it with normal methods but using a framework that can easily do it, like SBJson

In the end I worked it out.

I used JSONKit, which is quite easy to learn.
And just did 1 line of code:

NSString *shortUrl = [[retData objectFromJSONData] objectForKey:@"id"];

[Duncan C]

Originally Posted by dany_dev

that format is JSON, my advice is not to parse it with normal methods but using a framework that can easily do it, like SBJson

For something that simple, I think I'd avoid the overhead of including a JSON parser.

for the string:

{ "kind": "urlshortener#url", "id": "http://goo.gl/something", "longUrl": "http://somethinglonggggg/" }

I'd use the NSString method rangeOfString: @"http://" to find the beginning of the URL, then search from that offset to the next quote, build an NSRange from the beginning of the "http" up to but not including the quote, and use substringWithRange to get the URL.

Something like this:

NSString* JSON_String = @"{ \"kind\": \"urlshortener#url\", \"id\": \"http://goo.gl/something\", \"longUrl\": \"http://somethinglonggggg/\" }";
NSRange urlRange;

//Find the location of the first @"http://" in the returned JSON string
urlRange = [JSON_String rangeOfString: @"http://"];

//Create a substring that discards everything before the "http"
NSString* trimmedString = 
  [JSON_String substringFromIndex: urlRange.location];

//Find the first quote after the "http"
urlRange = [trimmedString rangeOfString @"\""];

//Create the final string for the shortened URL.
NSString* theShortenedURL = 
  [trimmedString substringToIndex: urlRange.location];

The code above assumes that the shortened URL will always appear before the long URL in the JSON string. If that's not true you'd have to first search for urlshortener tag, then search from that point for the "http".

Disclaimer: The code above was thrown together in a couple of minutes and has not been compiled, much less tested. My code usually has a few syntax errors on the first pass. I'm a terrible proofreader. I can spot logic problems pretty quickly, but syntax errors are another story. The code above also doesn't include any error checking. That's left as an "exercise for the reader."

[dany_dev]

yes, maybe is reasonable in this specific case to use a "dirt way", but my advice should be considered as the "normal way".....also having only 2-3 things to parse do it manually is not the way IMHO.

[Duncan C]

Originally Posted by dany_dev

yes, maybe is reasonable in this specific case to use a "dirt way", but my advice should be considered as the "normal way".....also having only 2-3 things to parse do it manually is not the way IMHO.

Agreed.

[chrishannah]

In the end I kept the JSON parser, as i figured I might end up using multiple url shortener services and they may need it as well.

Thanks for the help!