NSURL pull out a single value for a key in a parameter string

Question

I have an NSURL:

serverCall?x=a&y=b&z=c

What is the quickest and most efficient way to get the value of y?

Thanks

Answer 1

UPDATE:

Since 2010 when this was written, it seems Apple has released a set of tools for that purpose. Please see the answers below for those.

Old-School Solution:

Well I know you said "the quickest way" but after I started doing a test with NSScanner I just couldn't stop. And while it is not the shortest way, it is sure handy if you are planning to use that feature a lot. I created a URLParser class that gets these vars using an NSScanner. The use is a simple as:

URLParser *parser = [[[URLParser alloc] initWithURLString:@"http://blahblahblah.com/serverCall?x=a&y=b&z=c&flash=yes"] autorelease]; NSString *y = [parser valueForVariable:@"y"]; NSLog(@"%@", y); //b NSString *a = [parser valueForVariable:@"a"]; NSLog(@"%@", a); //(null) NSString *flash = [parser valueForVariable:@"flash"]; NSLog(@"%@", flash); //yes 

And the class that does this is the following (*source files at the bottom of the post):

URLParser.h

@interface URLParser : NSObject {     NSArray *variables; }  @property (nonatomic, retain) NSArray *variables;  - (id)initWithURLString:(NSString *)url; - (NSString *)valueForVariable:(NSString *)varName;  @end 

URLParser.m

@implementation URLParser @synthesize variables;  - (id) initWithURLString:(NSString *)url{     self = [super init];     if (self != nil) {         NSString *string = url;         NSScanner *scanner = [NSScanner scannerWithString:string];         [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"&?"]];         NSString *tempString;         NSMutableArray *vars = [NSMutableArray new];         [scanner scanUpToString:@"?" intoString:nil];       //ignore the beginning of the string and skip to the vars         while ([scanner scanUpToString:@"&" intoString:&tempString]) {             [vars addObject:[tempString copy]];         }         self.variables = vars;         [vars release];     }     return self; }  - (NSString *)valueForVariable:(NSString *)varName {     for (NSString *var in self.variables) {         if ([var length] > [varName length]+1 && [[var substringWithRange:NSMakeRange(0, [varName length]+1)] isEqualToString:[varName stringByAppendingString:@"="]]) {             NSString *varValue = [var substringFromIndex:[varName length]+1];             return varValue;         }     }     return nil; }  - (void) dealloc{     self.variables = nil;     [super dealloc]; }  @end 

*if you don't like copying and pasting you can just download the source files - I made a quick blog post about this here.