NSUserDefaults

Inherits From

NSObject
NSUserDefaults

NSObject
NSUserDefaults

Conforms To

Import Statement

Objective-C

@import Foundation;

Swift

import Foundation

Availability

Available in iOS 2.0 and later

The NSUserDefaults class provides a programmatic interface for interacting with the defaults system. The defaults system allows an application to customize its behavior to match a user’s preferences. For example, you can allow users to determine what units of measurement your application displays or how often documents are automatically saved. Applications record such preferences by assigning values to a set of parameters in a user’s defaults database. The parameters are referred to as defaults since they’re commonly used to determine an application’s default state at startup or the way it acts by default.

At runtime, you use an NSUserDefaults object to read the defaults that your application uses from a user’s defaults database. NSUserDefaults caches the information to avoid having to open the user’s defaults database each time you need a default value. The synchronize method, which is automatically invoked at periodic intervals, keeps the in-memory cache in sync with a user’s defaults database.

The NSUserDefaults class provides convenience methods for accessing common types such as floats, doubles, integers, Booleans, and URLs. A default object must be a property list, that is, an instance of (or for collections a combination of instances of): NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary. If you want to store any other type of object, you should typically archive it to create an instance of NSData. For more details, see Preferences and Settings Programming Guide.

Values returned from NSUserDefaults are immutable, even if you set a mutable object as the value. For example, if you set a mutable string as the value for "MyStringDefault", the string you later retrieve using stringForKey: will be immutable.

A defaults database is created automatically for each user. The NSUserDefaults class does not currently support per-host preferences. To do this, you must use the CFPreferences API (see Preferences Utilities Reference). However, NSUserDefaults correctly reads per-host preferences, so you can safely mix CFPreferences code with NSUserDefaults code.

If your application supports managed environments, you can use an NSUserDefaults object to determine which preferences are managed by an administrator for the benefit of the user. Managed environments correspond to computer labs or classrooms where an administrator or teacher may want to configure the systems in a particular way. In these situations, the teacher can establish a set of default preferences and force those preferences on users. If a preference is managed in this manner, applications should prevent users from editing that preference by disabling any appropriate controls.

The NSUserDefaults class is thread-safe.

Persistence of NSURL and file reference URLs

When using NSURL instances to refer to files within a process, it's important to make the distinction between location-based tracking (file: scheme URLs that are basically paths) versus filesystem identity tracking (file: scheme URLs that are file reference URLs). When persisting an NSURL, you should take that behavior into consideration. If your application tracks the resource being located by its identity so that it can be found if the user moves the file, then you should explicitly write the NSURL's bookmark data or encode a file reference URL.

If you want to track a file by reference but you require explicit control over when resolution occurs, you should take care to write out bookmark data to NSUserDefaults rather than rely on -[NSUserDefaults setURL:forKey:]. This allows you to call +[NSURL URLByResolvingBookmarkData:options:relativeToURL:bookmarkDataIsStale:error:] at a time when you know your application will be able to handle the potential I/O or required user interface interactions.

Sandbox Considerations

A sandboxed app cannot access or modify the preferences for any other app. (For example, if you add another app's domain using the addSuiteNamed: method, you do not gain access to that app's preferences.)

Attempting to access or modify another app's preferences does not result in an error, but when you do, OS X actually reads and writes files located within your app's container, rather than the actual preference files for the other application.

Getting the Shared NSUserDefaults Instance

standardUserDefaults() + standardUserDefaults
Returns the shared defaults object.

Declaration

Swift

class func standardUserDefaults() -> NSUserDefaults

Objective-C

+ (NSUserDefaults *)standardUserDefaults

Return Value

The shared defaults object.
Discussion

If the shared defaults object does not exist yet, it is created with a search list containing the names of the following domains, in this order:
- NSArgumentDomain, consisting of defaults parsed from the application’s arguments
- A domain identified by the application’s bundle identifier
- NSGlobalDomain, consisting of defaults meant to be seen by all applications
- Separate domains for each of the user’s preferred languages
- NSRegistrationDomain, a set of temporary defaults whose values can be set by the application to ensure that searches will always be successful
The defaults are initialized for the current user. Subsequent modifications to the standard search list remain in effect even when this method is invoked again—the search list is guaranteed to be standard only the first time this method is invoked.
Availability

Available in iOS 2.0 and later.
resetStandardUserDefaults() + resetStandardUserDefaults

Synchronizes any changes made to the shared user defaults object and releases it from memory.

Declaration

Swift

class func resetStandardUserDefaults()

Objective-C

+ (void)resetStandardUserDefaults

Discussion

A subsequent invocation of standardUserDefaults creates a new shared user defaults object with the standard search list.

Availability

Available in iOS 2.0 and later.

Initializing an NSUserDefaults Object

init() - init

Returns an NSUserDefaults object initialized with the defaults for the current user account.

Declaration

Swift

convenience init()

Objective-C

- (instancetype)init

Return Value

An initialized NSUserDefaults object whose argument and registration domains are already set up.

Discussion

This method does not put anything in the search list. Invoke it only if you’ve allocated your own NSUserDefaults instance instead of using the shared one.

Availability

Available in iOS 2.0 and later.

See Also

+ standardUserDefaults
- initWithUser: (iOS 7.0)

Returns an NSUserDefaults object initialized with the defaults for the specified user account.

Deprecation Statement

This method was never implemented to return anything but the defaults for the current user. Use standardUserDefaults instead.

Declaration

Objective-C

- (id)initWithUser:(NSString *)username

Parameters

username

The name of the user account.

Return Value

An initialized NSUserDefaults object whose argument and registration domains are already set up. If the current user does not have access to the specified user account, this method returns nil.

Discussion

This method does not put anything in the search list. Invoke it only if you’ve allocated your own NSUserDefaults instance instead of using the shared one.

You do not normally use this method to initialize an instance of NSUserDefaults. Applications used by a superuser might use this method to update the defaults databases for a number of users. The user who started the application must have appropriate access (read, write, or both) to the defaults database of the new user, or this method returns nil.

Special Considerations

This method was never implemented to do anything except return the defaults for the current user.

Availability

Available in iOS 2.0 and later.

Deprecated in iOS 7.0.

See Also

+ standardUserDefaults


    
      
           init(suiteName:)
      
      
           - initWithSuiteName:

Designated Initializer

Returns an NSUserDefaults object initialized with the defaults for the specified app group.

Declaration

Swift

init?(suiteName suitename: String?)

Objective-C

- (instancetype)initWithSuiteName:(NSString *)suitename

Parameters


  suitename

The name of the app group.

If you pass nil to this parameter, the system uses the default search list that the standardUserDefaults class method uses.

Return Value

An initialized NSUserDefaults object whose argument and registration domains are already set up.

Discussion

Use this method in scenarios such as:

When developing an app suite, to share preferences or other data among the apps
When developing an app extension, to share preferences or other data between the extension and its containing app

Availability

Available in iOS 7.0 and later.

Registering Defaults

registerDefaults(_:) - registerDefaults:

Adds the contents of the specified dictionary to the registration domain.

Declaration

Swift

func registerDefaults(_ registrationDictionary: [String : AnyObject])

Objective-C

- (void)registerDefaults:(NSDictionary<NSString *,id> *)dictionary

Parameters

dictionary

The dictionary of keys and values you want to register.

Discussion

If there is no registration domain, one is created using the specified dictionary, and NSRegistrationDomain is added to the end of the search list.

The contents of the registration domain are not written to disk; you need to call this method each time your application starts. You can place a plist file in the application's Resources directory and call registerDefaults: with the contents that you read in from that file.

Availability

Available in iOS 2.0 and later.

Getting Default Values

arrayForKey(_:) - arrayForKey:

Returns the array associated with the specified key.

Declaration

Swift

func arrayForKey(_ defaultName: String) -> [AnyObject]?

Objective-C

- (NSArray *)arrayForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The array associated with the specified key, or nil if the key does not exist or its value is not an NSArray object.

Special Considerations

The returned array and its contents are immutable, even if the values you originally set were mutable.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:
boolForKey(_:) - boolForKey:

Returns the Boolean value associated with the specified key.

Declaration

Swift

func boolForKey(_ defaultName: String) -> Bool

Objective-C

- (BOOL)boolForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

If a boolean value is associated with defaultName in the user defaults, that value is returned. Otherwise, NOfalse is returned.

Availability

Available in iOS 2.0 and later.

See Also

– setBool:forKey:
dataForKey(_:) - dataForKey:

Returns the data object associated with the specified key.

Declaration

Swift

func dataForKey(_ defaultName: String) -> NSData?

Objective-C

- (NSData *)dataForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The data object associated with the specified key, or nil if the key does not exist or its value is not an NSData object.

Special Considerations

The returned data object is immutable, even if the value you originally set was a mutable data object.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:
dictionaryForKey(_:) - dictionaryForKey:

Returns the dictionary object associated with the specified key.

Declaration

Swift

func dictionaryForKey(_ defaultName: String) -> [String : AnyObject]?

Objective-C

- (NSDictionary<NSString *,id> *)dictionaryForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The dictionary object associated with the specified key, or nil if the key does not exist or its value is not an NSDictionary object.

Special Considerations

The returned dictionary and its contents are immutable, even if the values you originally set were mutable.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:
floatForKey(_:) - floatForKey:

Returns the floating-point value associated with the specified key.

Declaration

Swift

func floatForKey(_ defaultName: String) -> Float

Objective-C

- (float)floatForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The floating-point value associated with the specified key. If the key does not exist, this method returns 0.

Availability

Available in iOS 2.0 and later.

See Also

– setFloat:forKey:
integerForKey(_:) - integerForKey:

Returns the integer value associated with the specified key..

Declaration

Swift

func integerForKey(_ defaultName: String) -> Int

Objective-C

- (NSInteger)integerForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The integer value associated with the specified key. If the specified key does not exist, this method returns 0.

Availability

Available in iOS 2.0 and later.

See Also

– setInteger:forKey:
objectForKey(_:) - objectForKey:

Returns the object associated with the first occurrence of the specified default.

Declaration

Swift

func objectForKey(_ defaultName: String) -> AnyObject?

Objective-C

- (id)objectForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The object associated with the specified key, or nil if the key was not found.

Discussion

This method searches the domains included in the search list in the order they are listed.

Special Considerations

The returned object is immutable, even if the value you originally set was mutable.

Availability

Available in iOS 2.0 and later.

See Also

– arrayForKey:
– dataForKey:
– dictionaryForKey:
– stringArrayForKey:
– stringForKey:
stringArrayForKey(_:) - stringArrayForKey:

Returns the array of strings associated with the specified key.

Declaration

Swift

func stringArrayForKey(_ defaultName: String) -> [String]?

Objective-C

- (NSArray<NSString *> *)stringArrayForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The array of NSString objects, or nil if the specified default does not exist, the default does not contain an array, or the array does not contain NSString objects.

Special Considerations

The returned array and its contents are immutable, even if the values you originally set were mutable.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:
stringForKey(_:) - stringForKey:

Returns the string associated with the specified key.

Declaration

Swift

func stringForKey(_ defaultName: String) -> String?

Objective-C

- (NSString *)stringForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

For string values, the string associated with the specified key. For number values, the string value of the number. Returns nil if the default does not exist or is not a string or number value.

Special Considerations

The returned string is immutable, even if the value you originally set was a mutable string.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:
doubleForKey(_:) - doubleForKey:

Returns the double value associated with the specified key.

Declaration

Swift

func doubleForKey(_ defaultName: String) -> Double

Objective-C

- (double)doubleForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The double value associated with the specified key. If the key does not exist, this method returns 0.

Availability

Available in iOS 2.0 and later.

See Also

– setDouble:forKey:
URLForKey(_:) - URLForKey:
Returns the NSURL instance associated with the specified key.

Declaration

Swift

func URLForKey(_ defaultName: String) -> NSURL?

Objective-C

- (NSURL *)URLForKey:(NSString *)defaultName

Parameters

defaultName

A key in the current user's defaults database.

Return Value

The NSURL instance value associated with the specified key. If the key does not exist, this method returns nil.
Discussion

When an NSURL is read using -[NSUserDefaults URLForKey:], the following logic is used:
1. If the value for the key is an NSData, the NSData is used as the argument to +[NSKeyedUnarchiver unarchiveObjectWithData:]. If the NSData can be unarchived as an NSURL, the NSURL is returned otherwise nil is returned.
2. If the value for this key was a file reference URL, the file reference URL will be created but its bookmark data will not be resolved until the NSURL instance is later used (e.g. at -[NSData initWithContentsOfURL:]).
3. If the value for the key is an NSString which begins with a ~, the NSString will be expanded using -[NSString stringByExpandingTildeInPath] and a file: scheme NSURL will be created from that.
Availability

Available in iOS 4.0 and later.

See Also

– setURL:forKey:

Setting Default Values

setBool(_:forKey:) - setBool:forKey:

Sets the value of the specified default key to the specified Boolean value.

Declaration

Swift

func setBool(_ value: Bool, forKey defaultName: String)

Objective-C

- (void)setBool:(BOOL)value forKey:(NSString *)defaultName

Parameters

value

The Boolean value to store in the defaults database.

defaultName

The key with which to associate with the value.

Discussion

Invokes setObject:forKey: as part of its implementation.

Availability

Available in iOS 2.0 and later.

See Also

– boolForKey:
setFloat(_:forKey:) - setFloat:forKey:

Sets the value of the specified default key to the specified floating-point value.

Declaration

Swift

func setFloat(_ value: Float, forKey defaultName: String)

Objective-C

- (void)setFloat:(float)value forKey:(NSString *)defaultName

Parameters

value

The floating-point value to store in the defaults database.

defaultName

The key with which to associate with the value.

Discussion

Invokes setObject:forKey: as part of its implementation.

Availability

Available in iOS 2.0 and later.

See Also

– floatForKey:
setInteger(_:forKey:) - setInteger:forKey:

Sets the value of the specified default key to the specified integer value.

Declaration

Swift

func setInteger(_ value: Int, forKey defaultName: String)

Objective-C

- (void)setInteger:(NSInteger)value forKey:(NSString *)defaultName

Parameters

value

The integer value to store in the defaults database.

defaultName

The key with which to associate with the value.

Discussion

Invokes setObject:forKey: as part of its implementation.

Availability

Available in iOS 2.0 and later.

See Also

– integerForKey:
setObject(_:forKey:) - setObject:forKey:

Sets the value of the specified default key in the standard application domain.

Declaration

Swift

func setObject(_ value: AnyObject?, forKey defaultName: String)

Objective-C

- (void)setObject:(id)value forKey:(NSString *)defaultName

Parameters

value

The object to store in the defaults database.

defaultName

The key with which to associate with the value.

Discussion

The value parameter can be only property list objects: NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary. For NSArray and NSDictionary objects, their contents must be property list objects. See What is a Property List? in Property List Programming Guide.

Setting a default has no effect on the value returned by the objectForKey: method if the same key exists in a domain that precedes the application domain in the search list.

Availability

Available in iOS 2.0 and later.

See Also

– removeObjectForKey:
setDouble(_:forKey:) - setDouble:forKey:

Sets the value of the specified default key to the double value.

Declaration

Swift

func setDouble(_ value: Double, forKey defaultName: String)

Objective-C

- (void)setDouble:(double)value forKey:(NSString *)defaultName

Parameters

value

The double value.

defaultName

The key with which to associate with the value.

Availability

Available in iOS 2.0 and later.
setURL(_:forKey:) - setURL:forKey:
Sets the value of the specified default key to the specified URL.

Declaration

Swift

func setURL(_ url: NSURL?, forKey defaultName: String)

Objective-C

- (void)setURL:(NSURL *)url forKey:(NSString *)defaultName

Parameters

url

The NSURL to store in the defaults database.

defaultName

The key with which to associate with the value.
Discussion

When an NSURL is stored using -[NSUserDefaults setURL:forKey:], some adjustments are made:
1. Any non-file URL is written by calling +[NSKeyedArchiver archivedDataWithRootObject:] using the NSURL instance as the root object.
2. Any file reference file: scheme URL will be treated as a non-file URL, and information which makes this URL compatible with 10.5 systems will also be written as part of the archive as well as its minimal bookmark data.
3. Any path-based file: scheme URL is written by first taking the absolute URL, getting the path from that and then determining if the path can be made relative to the user's home directory. If it can, the string is abbreviated by using stringByAbbreviatingWithTildeInPath and written out. This allows pre-10.6 clients to read the default and use -[NSString stringByExpandingTildeInPath] to use this information.
Availability

Available in iOS 4.0 and later.

See Also

– URLForKey:

Removing Defaults

removeObjectForKey(_:) - removeObjectForKey:

Removes the value of the specified default key in the standard application domain.

Declaration

Swift

func removeObjectForKey(_ defaultName: String)

Objective-C

- (void)removeObjectForKey:(NSString *)defaultName

Parameters

defaultName

The key whose value you want to remove.

Discussion

Removing a default has no effect on the value returned by the objectForKey: method if the same key exists in a domain that precedes the standard application domain in the search list.

Availability

Available in iOS 2.0 and later.

See Also

– setObject:forKey:

Maintaining Persistent Domains

synchronize() - synchronize

Writes any modifications to the persistent domains to disk and updates all unmodified persistent domains to what is on disk.

Declaration

Swift

func synchronize() -> Bool

Objective-C

- (BOOL)synchronize

Return Value

YEStrue if the data was saved successfully to disk, otherwise NOfalse.

Discussion

Because this method is automatically invoked at periodic intervals, use this method only if you cannot wait for the automatic synchronization (for example, if your application is about to exit) or if you want to update the user defaults to what is on disk even though you have not made any changes.

Availability

Available in iOS 2.0 and later.

See Also

– persistentDomainForName:
– removePersistentDomainForName:
– setPersistentDomain:forName:
persistentDomainForName(_:) - persistentDomainForName:

Returns a dictionary containing the keys and values in the specified persistent domain.

Declaration

Swift

func persistentDomainForName(_ domainName: String) -> [String : AnyObject]?

Objective-C

- (NSDictionary<NSString *,id> *)persistentDomainForName:(NSString *)domainName

Parameters

domainName

The domain whose keys and values you want.

Return Value

A dictionary containing the keys. The keys are names of defaults and the value corresponding to each key is a property list object (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary).

Availability

Available in iOS 2.0 and later.

See Also

– removePersistentDomainForName:
– setPersistentDomain:forName:
- persistentDomainNames (iOS 7.0)

Returns an array of the current persistent domain names.

Deprecation Statement

Instead of using this method, you should track the domains you add if you want to later retrieve them with persistentDomainForName:.

Declaration

Objective-C

- (NSArray *)persistentDomainNames

Return Value

An array of NSString objects containing the domain names.

Discussion

You can get the keys and values for each domain by passing the returned domain names to the persistentDomainForName: method.

Availability

Available in iOS 2.0 and later.

Deprecated in iOS 7.0.

See Also

– removePersistentDomainForName:
– setPersistentDomain:forName:
removePersistentDomainForName(_:) - removePersistentDomainForName:

Removes the contents of the specified persistent domain from the user’s defaults.

Declaration

Swift

func removePersistentDomainForName(_ domainName: String)

Objective-C

- (void)removePersistentDomainForName:(NSString *)domainName

Parameters

domainName

The domain whose keys and values you want.

Discussion

When a persistent domain is changed, an NSUserDefaultsDidChangeNotification is posted.

Availability

Available in iOS 2.0 and later.

See Also

– setPersistentDomain:forName:
– persistentDomainNames


    
      
           setPersistentDomain(_:forName:)
      
      
           - setPersistentDomain:forName:

Sets the dictionary for the specified persistent domain.

Declaration

Swift

func setPersistentDomain(_ domain: [String : AnyObject], forName domainName: String)

Objective-C

- (void)setPersistentDomain:(NSDictionary<NSString *,id> *)domain forName:(NSString *)domainName

Parameters

`domain`	The dictionary of keys and values you want to assign to the domain.
`domainName`	The domain whose keys and values you want to set. This value should be equal to your application's bundle identifier.

Discussion

When a persistent domain is changed, an NSUserDefaultsDidChangeNotification is posted.

Availability

Available in iOS 2.0 and later.

Accessing Managed Environment Keys

objectIsForcedForKey(_:) - objectIsForcedForKey:

Returns a Boolean value indicating whether the specified key is managed by an administrator.

Declaration

Swift

func objectIsForcedForKey(_ key: String) -> Bool

Objective-C

- (BOOL)objectIsForcedForKey:(NSString *)key

Parameters

key

The key whose status you want to check.

Return Value

YEStrue if the value of the specified key is managed by an administrator, otherwise NOfalse.

Discussion

This method assumes that the key is a preference associated with the current user and application. For managed keys, the application should disable any user interface that allows the user to modify the value of key.

Availability

Available in iOS 2.0 and later.

See Also

– objectIsForcedForKey:inDomain:
objectIsForcedForKey(_:inDomain:) - objectIsForcedForKey:inDomain:

Returns a Boolean value indicating whether the key in the specified domain is managed by an administrator.

Declaration

Swift

func objectIsForcedForKey(_ key: String, inDomain domain: String) -> Bool

Objective-C

- (BOOL)objectIsForcedForKey:(NSString *)key inDomain:(NSString *)domain

Parameters

key

The key whose status you want to check.

domain

The domain of the key.

Return Value

YEStrue if the key is managed by an administrator in the specified domain, otherwise NOfalse.

Discussion

This method assumes that the key is a preference associated with the current user. For managed keys, the application should disable any user interface that allows the user to modify the value of key.

Availability

Available in iOS 2.0 and later.

See Also

– objectIsForcedForKey:

Managing the Search List

dictionaryRepresentation() - dictionaryRepresentation

Returns a dictionary that contains a union of all key-value pairs in the domains in the search list.

Declaration

Swift

func dictionaryRepresentation() -> [String : AnyObject]

Objective-C

- (NSDictionary<NSString *,id> *)dictionaryRepresentation

Return Value

A dictionary containing the keys. The keys are names of defaults and the value corresponding to each key is a property list object (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary).

Discussion

As with objectForKey:, key-value pairs in domains that are earlier in the search list take precedence. The combined result does not preserve information about which domain each entry came from.

Availability

Available in iOS 2.0 and later.

Maintaining Volatile Domains

removeVolatileDomainForName(_:) - removeVolatileDomainForName:

Removes the specified volatile domain from the user’s defaults.

Declaration

Swift

func removeVolatileDomainForName(_ domainName: String)

Objective-C

- (void)removeVolatileDomainForName:(NSString *)domainName

Parameters

domainName

The volatile domain you want to remove.

Availability

Available in iOS 2.0 and later.

See Also

– setVolatileDomain:forName:
setVolatileDomain(_:forName:) - setVolatileDomain:forName:

Sets the dictionary for the specified volatile domain.

Declaration

Swift

func setVolatileDomain(_ domain: [String : AnyObject], forName domainName: String)

Objective-C

- (void)setVolatileDomain:(NSDictionary<NSString *,id> *)domain forName:(NSString *)domainName

Parameters

domain

The dictionary of keys and values you want to assign to the domain.

domainName

The domain whose keys and values you want to set.

Discussion

This method raises an NSInvalidArgumentException if a volatile domain with the specified name already exists.

Availability

Available in iOS 2.0 and later.

See Also

– volatileDomainForName:
– volatileDomainNames
volatileDomainForName(_:) - volatileDomainForName:

Returns the dictionary for the specified volatile domain.

Declaration

Swift

func volatileDomainForName(_ domainName: String) -> [String : AnyObject]

Objective-C

- (NSDictionary<NSString *,id> *)volatileDomainForName:(NSString *)domainName

Parameters

domainName

The domain whose keys and values you want.

Return Value

The dictionary of keys and values belonging to the domain. The keys in the dictionary are names of defaults, and the value corresponding to each key is a property list object (NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary).

Availability

Available in iOS 2.0 and later.

See Also

– removeVolatileDomainForName:
– setVolatileDomain:forName:
volatileDomainNames volatileDomainNames Property

The current volatile domain names. (read-only)

Declaration

Swift

var volatileDomainNames: [String] { get }

Objective-C

@property(readonly, copy) NSArray <NSString *> *volatileDomainNames

Discussion

The domain names are represented as strings. You can get the contents of each domain by passing the returned domain names to the volatileDomainForName: method.

Availability

Available in iOS 2.0 and later.

See Also

– removeVolatileDomainForName:
– setVolatileDomain:forName:

Maintaining Suites

addSuiteNamed(_:) - addSuiteNamed:

Inserts the specified domain name into the receiver’s search list.

Declaration

Swift

func addSuiteNamed(_ suiteName: String)

Objective-C

- (void)addSuiteNamed:(NSString *)suiteName

Parameters

suiteName

The domain name to insert. This domain is inserted after the application domain.

Discussion

The suiteName domain is similar to a bundle identifier string, but is not necessarily tied to a particular application or bundle. A suite can be used to hold preferences that are shared between multiple applications.

Searches of preferences tied to a suite follow the normal pattern, searching first for current user, current host, then

Availability

Available in iOS 2.0 and later.

See Also

+ standardUserDefaults
– removeSuiteNamed:
removeSuiteNamed(_:) - removeSuiteNamed:

Removes the specified domain name from the receiver’s search list.

Declaration

Swift

func removeSuiteNamed(_ suiteName: String)

Objective-C

- (void)removeSuiteNamed:(NSString *)suiteName

Parameters

suiteName

The domain name to remove.

Availability

Available in iOS 2.0 and later.

See Also

– addSuiteNamed:

Constants

NSUserDefaults Domains
These constants specify various user defaults domains.

Declaration

Swift

let NSGlobalDomain: String let NSArgumentDomain: String let NSRegistrationDomain: String

Objective-C

extern NSString *NSGlobalDomain; extern NSString *NSArgumentDomain; extern NSString *NSRegistrationDomain;

Constants
- NSGlobalDomain
  
  NSGlobalDomain
  
  The domain consisting of defaults meant to be seen by all applications.
  
  Available in iOS 2.0 and later.
- NSArgumentDomain
  
  NSArgumentDomain
  
  The domain consisting of defaults parsed from the application’s arguments. These are one or more pairs of the form -default value included in the command-line invocation of the application.
  
  Available in iOS 2.0 and later.
- NSRegistrationDomain
  
  NSRegistrationDomain
  
  The domain consisting of a set of temporary defaults whose values can be set by the application to ensure that searches will always be successful.
  
  Available in iOS 2.0 and later.

Notifications

NSUserDefaultsDidChangeNotification NSUserDefaultsDidChangeNotification

This notification is posted when a change is made to defaults in a persistent domain.
The notification object is the NSUserDefaults object. This notification does not contain a userInfo dictionary.

Declaration

Swift

let NSUserDefaultsDidChangeNotification: String

Import Statement

Objective-C

@import Foundation;

Swift

import Foundation

Availability

Available in iOS 2.0 and later.

`value`	The Boolean value to store in the defaults database.
`defaultName`	The key with which to associate with the value.

`value`	The floating-point value to store in the defaults database.
`defaultName`	The key with which to associate with the value.

`value`	The integer value to store in the defaults database.
`defaultName`	The key with which to associate with the value.

`value`	The object to store in the defaults database.
`defaultName`	The key with which to associate with the value.

`value`	The double value.
`defaultName`	The key with which to associate with the value.

`url`	The `NSURL` to store in the defaults database.
`defaultName`	The key with which to associate with the value.

`key`	The key whose status you want to check.
`domain`	The domain of the key.

NSUserDefaults

Persistence of NSURL and file reference URLs

Sandbox Considerations

Getting the Shared NSUserDefaults Instance

Declaration

Return Value

Discussion

Availability

Declaration

Discussion

Availability

Initializing an NSUserDefaults Object

Declaration

Return Value

Discussion

Availability

See Also

Deprecation Statement

Declaration

Parameters

Return Value

Discussion

Special Considerations

Availability

See Also

Declaration

Parameters

Return Value

Discussion

Availability

Registering Defaults

Declaration

Parameters

Discussion

Availability

Getting Default Values

Declaration

Parameters

Return Value

Special Considerations

Availability

See Also

Declaration

Parameters

Return Value

Availability

See Also

Declaration

Parameters

Return Value

Special Considerations

Availability

See Also

Declaration

Parameters

Return Value

Special Considerations

Availability

See Also

Declaration

Parameters

Return Value

Availability

See Also

Declaration

Parameters

Return Value

Availability

See Also

Declaration

Parameters

Return Value

Discussion

Special Considerations

Availability

See Also

Declaration

Parameters

Return Value

Special Considerations