Question

Can anyone please review the following method and tell me if it is necessary to release the enumerator for the dictionary keys after using it? I m new to objective c and not always sure, when to release variables returned from the SDK methods. I suppose the keyEnumerator method returns an autoreleased instance so I don t have to care about it when I m finished with it. Right?

Hmm.. maybe anything else wrong in this method? ;)

#import "NSDictionaryURLEncoding.h"
#import <Foundation/NSURL.h>

@implementation NSDictionary(URLEncoding)

-(NSString *)urlEncoded
{
   NSEnumerator *keyEnum = [self keyEnumerator];
   NSString *currKey;
   NSString *currObject;
   NSMutableString *result = [NSMutableString stringWithCapacity: 64];

   while ((currKey = [keyEnum nextObject]) != nil)
   {
      if ([result length] > 0)
      {
         [result appendString: @"&"];
      }
      currObject = [[self objectForKey: currKey] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
      currKey = [currKey stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

      [result appendString: [NSString stringWithFormat:@"%@=%@", currKey, currObject]];
   }
   return result;
}

@end

Answer 1

You must never release objects for which you did not call the alloc method if you also didn t retain them. See the Memory Management Programming Guide for Cocoa.

Also, if you re programming for the iPhone OS or if you are targetting Mac OS X 10.5 or later, I suggest you use the for(... in ...) language construct to enumerate through your dictionary. It s much faster than using enumerators.

for(NSString* currKey in self)
{
    NSString* currObject = [self objectForKey:currKey];
    // the rest of your loop code
}

You should read the Fast Enumeration section of the Objective-C Programming Language Reference.

I also suggest, as a friendly advice, that you don t extend NSDictionary or create a category on it unless you really, really need it.

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