Best way to parse URL string to get values for keys?

Question

I need to parse a URL string like this one:

&ad_eurl=http://www.youtube.com/video/4bL4FI1Gz6s&hl=it_IT&iv_logging_level=3&ad_flags=0&endscreen_module=http://s.ytimg.com/yt/swfbin/endscreen-vfl6o3XZn.swf&cid=241&cust_gender=1&avg_rating=4.82280613104 

I need to split the NSString up into the signle parts like cid=241 and &avg_rating=4.82280613104. I've been doing this with substringWithRange: but the values return in a random order, so that messes it up. Is there any class that allows easy parsing where you can basically convert it to NSDictionary to be able to read the value for a key (for example ValueForKey:cid should return 241). Or is there just another easier way to parse it than using NSMakeRange to get a substring?

Answer 1

edit (June 2018): this answer is better. Apple added NSURLComponents in iOS 7.

I would create a dictionary, get an array of the key/value pairs with

NSMutableDictionary *queryStringDictionary = [[NSMutableDictionary alloc] init]; NSArray *urlComponents = [urlString componentsSeparatedByString:@"&"]; 

Then populate the dictionary :

for (NSString *keyValuePair in urlComponents) {     NSArray *pairComponents = [keyValuePair componentsSeparatedByString:@"="];     NSString *key = [[pairComponents firstObject] stringByRemovingPercentEncoding];     NSString *value = [[pairComponents lastObject] stringByRemovingPercentEncoding];      [queryStringDictionary setObject:value forKey:key]; } 

You can then query with

[queryStringDictionary objectForKey:@"ad_eurl"]; 

This is untested, and you should probably do some more error tests.

Answer 2

I also answered this at https://stackoverflow.com/a/26406478/215748.

You can use queryItems in URLComponents.

When you get this property’s value, the NSURLComponents class parses the query string and returns an array of NSURLQueryItem objects, each of which represents a single key-value pair, in the order in which they appear in the original query string.

let url = "http://example.com?param1=value1&param2=param2" let queryItems = URLComponents(string: url)?.queryItems let param1 = queryItems?.filter({$0.name == "param1"}).first print(param1?.value) 

Alternatively, you can add an extension on URL to make things easier.

extension URL {     var queryParameters: QueryParameters { return QueryParameters(url: self) } }  class QueryParameters {     let queryItems: [URLQueryItem]     init(url: URL?) {         queryItems = URLComponents(string: url?.absoluteString ?? "")?.queryItems ?? []         print(queryItems)     }     subscript(name: String) -> String? {         return queryItems.first(where: { $0.name == name })?.value     } } 

You can then access the parameter by its name.

let url = URL(string: "http://example.com?param1=value1&param2=param2")! print(url.queryParameters["param1"])