CODEWITHSUNDEEP
swiftmacoscocoansuserdefaults
drootang
drootang

Reputation: 2503

How does one programmatically delete a preference from the NSGlobalDomain?

This is a simple task from the terminal:

defaults delete -g <key>

I'd like to do this in Swift using NSUserDefaults. The documentation says:

If you want to change the value of a preference in the global domain, write that same preference to the application domain with the new value.

This simply sets a new value for the same key in the application domain so that when NSUserDefaults retrieves the value for the key in the future, it will find the new value in the application domain before it searches the global domain.

Is there some way to either:

  1. delete the key from the NSGlobalDomain, or
  2. set a new value for the key in NSGlobalDomain

using NSUserDefaults?

I know I can use NSTask, for example, to run defaults delete -g <key>, but I consider that a workaround (a valid one).

Upvotes: 2

Views: 1061

Answers (1)

Ken Thomases
Ken Thomases

Reputation: 90531

You can try this, but it's not really a good idea:

var defaults = NSUserDefaults.standardUserDefaults()
var globalDomain = defaults.persistentDomainForName(NSGlobalDomain)
globalDomain.removeObjectForKey(someKey)
defaults.setPersistentDomain(globalDomain, forName:NSGlobalDomain)

The main problem is a race condition with other processes or threads. If something changes the global domain between the time you read it and when you write it back, you undo those changes, even if they didn't involve the key you were manipulating. Also, you're potentially reading and writing a large dictionary, doing a lot more work than actually necessary.

Probably better to drop down to the CFPreferences API:

CFPreferencesSetValue(someKey, nil, kCFPreferencesAnyApplication,
                      kCFPreferencesCurrentUser, kCFPreferencesCurrentHost)

Upvotes: 5

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