Parsing JSON iOS - iphone

Question

I'm trying to parse some JSON in iOS to get a URL from google. I've gotten pretty far (see code below), the problem is since I've never worked with JSON before, I'm not really sure how things are defined. How can I look for an object that's inside another object?
For example if I want to get the first unescapedUrl here how can I do that? I tried simply using objectForKey, but it didn't work.. I'm guessing I'm going to have to specify the exact path. How can I do that?
Here's the code I'm using:
#define kBgQueue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) //1
#define kLatestSearchURL [NSURL URLWithString: #"https://ajax.googleapis.com/ajax/services/search/images?v=1.0&q=monkey"] //2
#import "ViewController.h"
#interface NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress;
-(NSData*)toJSON;
#end
#implementation NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress
{
NSData* data = [NSData dataWithContentsOfURL: [NSURL URLWithString: urlAddress] ];
__autoreleasing NSError* error = nil;
id result = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
if (error != nil) return nil;
return result;
}
-(NSData*)toJSON
{
NSError* error = nil;
id result = [NSJSONSerialization dataWithJSONObject:self options:kNilOptions error:&error];
if (error != nil) return nil;
return result;
}
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
dispatch_async(kBgQueue, ^{
NSData* data = [NSData dataWithContentsOfURL: kLatestSearchURL];
[self performSelectorOnMainThread:#selector(fetchedData:) withObject:data waitUntilDone:YES];
});
}
- (void)fetchedData:(NSData *)responseData {
NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
options:kNilOptions
error:&error];
// ---------------------------- Will Start Parsing Here ------------------------------
}
#end

Answer 1

God save literals (Xcode 4.5 and iOS 6.0 or later SDK, LLVM Compiler 4.0 required). Deploys back to iOS 5.
NSString *url = resp[#"responseData"][#"results"][0][#"unescapedUrl"];

Answer 2

You can use objectForKey: for dictionaries and objectAtIndex: for arrays:
NSString *url = [[[[resp objectForKey:#"responseData"]
objectForKey:#"results"]
objectAtIndex:0]
objectForKey:#"unescapedUrl"];