Convert NSData to NSDictionary or Convert NSData to NSArray.

-(void)parseDataFromServer:(NSData*)responseData 
{
NSError* error;
// If response JSON starts with {}, it represents dictionary
NSDictionary *dicData = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
// If response JSON starts with [], it represents array
NSArray* arrData = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error]; 

if (error) NSLog(@"%@",error.localizedDescription);

}

Class: NSJSONSerialization



Method: + (NSData *)dataWithJSONObject:(id)obj

                               options:(NSJSONWritingOptions)opt  

                                 error:(NSError **)error;

Reference Links: Apple Doc