Parse NSURL path and query on iOS

Alright, I got antsy and wrote a solution for extending NSString through Categories. I haven't tested this yet, but if you want to use it, go for it.

@interface NSString (ParseCategory)
- (NSMutableDictionary *)explodeToDictionaryInnerGlue:(NSString *)innerGlue outterGlue:(NSString *)outterGlue;
@end

@implementation NSString (ParseCategory)

- (NSMutableDictionary *)explodeToDictionaryInnerGlue:(NSString *)innerGlue outterGlue:(NSString *)outterGlue {
    // Explode based on outter glue
    NSArray *firstExplode = [self componentsSeparatedByString:outterGlue];
    NSArray *secondExplode;

    // Explode based on inner glue
    NSInteger count = [firstExplode count];
    NSMutableDictionary *returnDictionary = [NSMutableDictionary dictionaryWithCapacity:count];
    for (NSInteger i = 0; i < count; i++) {
        secondExplode = [(NSString *)[firstExplode objectAtIndex:i] componentsSeparatedByString:innerGlue];
        if ([secondExplode count] == 2) {
            [returnDictionary setObject:[secondExplode objectAtIndex:1] forKey:[secondExplode objectAtIndex:0]];
        }
    }

    return returnDictionary;
}

@end

It's called like this:

NSMutableDictionary *parsedQuery = [[myNSURL query] explodeToDictionaryInnerGlue:@"=" outterGlue=@"&"]

For parsing the path portion of the NSURL (ie @"/partA/partB/partC"), just call this:

NSArray *parsedPath = [[nyNSURL path] componentsSeperatedByString:@"/"];

Be aware that parsedPath[0] will be an empty string because of the leading /!

EDIT - Here is a Category extension to NSURL for your usage pleasure. It strips the initial "/" so you don't have an empty 0 index.

@implementation NSURL (ParseCategory)

- (NSArray *)pathArray {
    // Create a character set for the slash character
    NSRange slashRange;
    slashRange.location = (unsigned int)'/';
    slashRange.length = 1;
    NSCharacterSet *slashSet = [NSCharacterSet characterSetWithRange:slashRange];

    // Get path with leading (and trailing) slashes removed
    NSString *path = [[self path] stringByTrimmingCharactersInSet:slashSet];

    return [path componentsSeparatedByCharactersInSet:slashSet];
}

- (NSDictionary *)queryDictionary {
    NSDictionary *returnDictionary = [[[[self query] explodeToDictionaryInnerGlue:@"=" outterGlue:@"&"] copy] autorelease];
    return returnDictionary;
}

@end

Sam Soffes created a well maintained Category for NSURL / NSDictionary. It can be found here: https://github.com/samsoffes/sstoolkit/

Heres what i use to parse the query string

// Parse the individual parameters
// parameters = @"hello=world&foo=bar";
NSMutableDictionary *dictParameters = [[NSMutableDictionary alloc] init];
NSArray *arrParameters = [parameters componentsSeparatedByString:@"&"];
for (int i = 0; i < [arrParameters count]; i++) {
    NSArray *arrKeyValue = [[arrParameters objectAtIndex:i] componentsSeparatedByString:@"="];
    if ([arrKeyValue count] >= 2) {
        NSMutableString *strKey = [NSMutableString stringWithCapacity:0];
        [strKey setString:[[[arrKeyValue objectAtIndex:0] lowercaseString] stringByReplacingPercentEscapesUsingEncoding: NSUTF8StringEncoding]];
        NSMutableString *strValue   = [NSMutableString stringWithCapacity:0];
        [strValue setString:[[[arrKeyValue objectAtIndex:1]  stringByReplacingOccurrencesOfString:@"+" withString:@" "] stringByReplacingPercentEscapesUsingEncoding: NSUTF8StringEncoding]];
        if (strKey.length > 0) [dictParameters setObject:strValue forKey:strKey];
    }
}
NSLog(@"Parameters: %@", dictParameters);

If you do decide to write one (I'm not sure there are existing methods of getting the components you want), you might want to use NSString's componentsSeparatedByString.

Introduced in iOS 8 and OS X 10.10 is NSURLQueryItem, which can be used to build queries. From the docs on NSURLQueryItem:

An NSURLQueryItem object represents a single name/value pair for an item in the query portion of a URL. You use query items with the queryItems property of an NSURLComponents object.

You can retrieve the query items from a URL by first creating NSURLComponents:

NSURL *url = [NSURL URLWithString:@"http://stackoverflow.com?q=ios&count=10"];
NSURLComponents *components = [NSURLComponents componentsWithURL:url 
                                               resolvingAgainstBaseURL:YES];
for (NSURLQueryItem *item in components.queryItems) {
    NSLog(@"name: %@, value: %@", item.name, item.value);
}
// name: q, value: ios
// name: count, value: 10

Note that they return value for -queryItems is an array, not a dictionary. This is because the following is a valid URL. Note the two identical "keys", foo.

http://google.com?foo=bar&foo=baz

To create a URL via query items, use the designated initializer queryItemWithName:value: and then add them to NSURLComponents to generate an NSURL. For example:

NSString *urlString = @"http://stackoverflow.com";
NSURLComponents *components = [NSURLComponents componentsWithString:urlString];
NSURLQueryItem *search = [NSURLQueryItem queryItemWithName:@"q" value:@"ios"];
NSURLQueryItem *count = [NSURLQueryItem queryItemWithName:@"count" value:@"10"];
components.queryItems = @[ search, count ];
NSURL *url = components.URL; // http://stackoverflow.com?q=ios&count=10

Notice that the question mark and ampersand are automatically handled. Creating an NSURL from a dictionary of parameters is as simple as:

NSDictionary *queryDictionary = @{ @"q": @"ios", @"count": @"10" };
NSMutableArray *queryItems = [NSMutableArray array];
for (NSString *key in queryDictionary) {
    NSURLQueryItem *item = [NSURLQueryItem queryItemWithName:key 
                                                       value:queryDictionary[key]]; 
    [queryItems addObject:item];
}
components.queryItems = queryItems;

I've also written a blog post with more details, Building NSURLs with NSURLQueryItems.