Cocoa Kid's Net Sweet bits of cocoa programming

Recipe #2: Initializing user preferences using NSUserDefaults

Recently I was in need of some user preferences. I read a guide on user defaults programming. Everything seemed easy and clear, but I still couldn’t find the thing that interested me most – initializing user preferences. By “initialization” I mean set defaults once so they can be overridden by user and not set again. For some reason I thought that I’d have to check each preferences key for its existence and set it accordingly.

Then the light bulb lit above my spiky head. I present you with the solution:

// Place this code into your apps delegate class
+ (void)initialize {
  NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
 
  // initialize the dictionary with default values
  NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys:@"fooValue", @"fooKey", @"barValue", @"barKey", nil];
 
  // and set them appropriately
  [defaults registerDefaults:appDefaults];
}

Now for refactored and more comfortable version you should use a separate plist for initializing user defaults. I believe it’s easier to add a row to plist file than add key/value pair into dictionary:

+ (void)initialize {
  // get the filename for "default defaults"
  NSString *defaultsFilename = [[NSBundle mainBundle] pathForResource:@"Defaults" ofType:@"plist"];
 
  // initialize a dictionary with contents of it
  NSDictionary *defaults = [NSDictionary dictionaryWithContentsOfFile:defaultsFilename];
 
  // register the stuff
  [[NSUserDefaults standardUserDefaults] registerDefaults:defaults];
}

The advantage of this approach is that even after updates to your app even unset defaults will be initialized (in case of newly added preferences).

That’s it! Kudos goes to Laurent Etiemble and Johan Kool for their answers to my question.