How to save local data in a Swift app

Question

I m currently working on a iOS app developed in Swift and I need to store some user-created content on the device but I can t seem to find a simple and quick way to store receive the users content on the device    Could someone explain how to store and access local storage   The idea is to store the data when the user executes an action and receive it when the app starts

User · Accepted Answer

The simplest solution if you are just storing two strings is NSUserDefaults, in Swift 3 this class has been renamed to just UserDefaults.

It's best to store your keys somewhere globally so that you can reuse them elsewhere in your code.

struct defaultsKeys {
    static let keyOne = "firstStringKey"
    static let keyTwo = "secondStringKey"
}

Swift 3.0, 4.0 & 5.0

// Setting

let defaults = UserDefaults.standard
defaults.set("Some String Value", forKey: defaultsKeys.keyOne)
defaults.set("Another String Value", forKey: defaultsKeys.keyTwo)

// Getting

let defaults = UserDefaults.standard
if let stringOne = defaults.string(forKey: defaultsKeys.keyOne) {
    print(stringOne) // Some String Value
}
if let stringTwo = defaults.string(forKey: defaultsKeys.keyTwo) {
    print(stringTwo) // Another String Value
}

Swift 2.0

// Setting

let defaults = NSUserDefaults.standardUserDefaults()
defaults.setObject("Some String Value", forKey: defaultsKeys.keyOne)
defaults.setObject("Another String Value", forKey: defaultsKeys.keyTwo)

// Getting

let defaults = NSUserDefaults.standardUserDefaults()
if let stringOne = defaults.stringForKey(defaultsKeys.keyOne) {
    print(stringOne) // Some String Value
}
if let stringTwo = defaults.stringForKey(defaultsKeys.keyTwo) {
    print(stringTwo) // Another String Value
}

For anything more serious than minor config, flags or base strings you should use some sort of persistent store - A popular option at the moment is Realm but you can also use SQLite or Apples very own CoreData.

User · Answer

For Swift 3  UserDefaults standard setValue token  forKey   user auth token   print    UserDefaults standard value forKey   user auth token

User · Answer

Using NSCoding and NSKeyedArchiver is another great option for data that s too complex for NSUserDefaults  but for which CoreData would be overkill   It also gives you the opportunity to manage the file structure more explicitly  which is great if you want to use encryption

User · Answer

Swift 5   None of the answers really cover in detail the default built in local storage capabilities   It can do far more than just strings   You have the following options straight from the apple documentation for  getting  data from the defaults   func object forKey  String  - gt  Any    Returns the object associated with the specified key   func url forKey  String  - gt  URL    Returns the URL associated with the specified key   func array forKey  String  - gt   Any     Returns the array associated with the specified key   func dictionary forKey  String  - gt   String   Any     Returns the dictionary object associated with the specified key   func string forKey  String  - gt  String    Returns the string associated with the specified key   func stringArray forKey  String  - gt   String     Returns the array of strings associated with the specified key   func data forKey  String  - gt  Data    Returns the data object associated with the specified key   func bool forKey  String  - gt  Bool   Returns the Boolean value associated with the specified key   func integer forKey  String  - gt  Int   Returns the integer value associated with the specified key   func float forKey  String  - gt  Float   Returns the float value associated with the specified key   func double forKey  String  - gt  Double   Returns the double value associated with the specified key   func dictionaryRepresentation   - gt   String   Any    Returns a dictionary that contains a union of all key-value pairs in the domains in the search list    Here are the options for  setting   func set Any   forKey  String    Sets the value of the specified default key   func set Float  forKey  String    Sets the value of the specified default key to the specified float value   func set Double  forKey  String    Sets the value of the specified default key to the double value   func set Int  forKey  String    Sets the value of the specified default key to the specified integer value   func set Bool  forKey  String    Sets the value of the specified default key to the specified Boolean value   func set URL   forKey  String    Sets the value of the specified default key to the specified URL    If are storing things like preferences and not a large data set these are perfectly fine options   Double Example   Setting   let defaults   UserDefaults standard var someDouble Double   0 5 defaults set someDouble  forKey   someDouble     Getting   let defaults   UserDefaults standard var someDouble Double   0 0 someDouble   defaults double forKey   someDouble     What is interesting about one of the getters is dictionaryRepresentation  this handy getter will take all your data types regardless what they are and put them into a nice dictionary that you can access by it s string name and give the correct corresponding data type when you ask for it back since it s of type  any    You can store your own classes and objects also using the func set Any   forKey  String  and func object forKey  String  - gt  Any  setter and getter accordingly   Hope this clarifies more the power of the UserDefaults class for storing local data   On the note of how much you should store and how often  Hardy Germany gave a good answer on that on this post  here is a quote from it     As many already mentioned  I m not aware of any SIZE limitation    except physical memory  to store data in a  plist  e g    UserDefaults   So it s not a question of HOW MUCH       The real question should be HOW OFTEN you write new   changed   values    And this is related to the battery drain this writes will   cause       IOS has no chance to avoid a physical write to  disk  if a single   value changed  just to keep data integrity  Regarding UserDefaults   this cause the whole file rewritten to disk       This powers up the  disk  and keep it powered up for a longer time and   prevent IOS to go to low power state    Something else to note as mentioned by user Mohammad Reza Farahani from this post is the asynchronous and synchronous nature of userDefaults      When you set a default value  it   s changed synchronously within your   process  and asynchronously to persistent storage and other processes    For example if you save and quickly close the program you may notice it does not save the results  this is because it s persisting asynchronously   You might not notice this all the time so if you plan on saving before quitting the program you may want to account for this by giving it some time to finish     Maybe someone has some nice solutions for this they can share in the comments

User · Answer

NsUserDefaults saves only small variable sizes  If you want to save many objects you can use CoreData as a native solution  or I created a library that helps you save objects as easy as  save   function  It   s based on SQLite   SundeedQLite  Check it out and tell me your comments

User · Answer

For someone who d not prefer to handle UserDefaults for some reasons  there s another option - NSKeyedArchiver  amp  NSKeyedUnarchiver  It helps save objects into a file using archiver  and load archived file to original objects      To archive object  let mutableData  NSMutableData   NSMutableData   let archiver  NSKeyedArchiver   NSKeyedArchiver forWritingWith  mutableData  archiver encode object  forKey  key  archiver finishEncoding   return mutableData write toFile  path  atomically  true      To unarchive objects  if let data   try  Data contentsOf  URL fileURLWithPath  path         let unarchiver   NSKeyedUnarchiver forReadingWith  data      let object   unarchiver decodeObject forKey  key      I ve write an simple utility to save load objects in local storage  used sample codes above  You might want to see this  https   github com DragonCherry LocalStorage

User · Answer

Okey so thanks to  bploat and the link to http   www codingexplorer com nsuserdefaults-a-swift-introduction   I ve found that the answer is quite simple for some basic string storage   let defaults   NSUserDefaults standardUserDefaults       Store defaults setObject  theGreatestName   forKey   username       Receive if let name   defaults stringForKey  username         print name         Will output  theGreatestName      I ve summarized it here http   ridewing se blog save-local-data-in-swift

User · Answer

For Swift 4 0  this got easier   let defaults   UserDefaults standard   Set defaults set passwordTextField text  forKey   Password     Get let myPassword   defaults string forKey   Password

User · Answer

Swift 3 0  Setter  Local Storage   let authtoken    12345         Userdefaults helps to store session data locally   let defaults   UserDefaults standard                                            defaults set authtoken  forKey   authtoken     defaults synchronize     Getter Local Storage   if UserDefaults standard string forKey   authtoken      nil      perform your task on success

User · Answer

They Say Use NSUserDefaults  When I was implementing long term  after app close  data storage for the first time  everything I read online pointed me towards NSUserDefaults  However  I wanted to store a dictionary and  although possible  it was proving to be a pain  I spent hours trying to get type-errors to go away   NSUserDefaults is Also Limited in Function  Further reading revealed how the read write of NSUserDefaults really forces the app to read write everything or nothing  all at once  so it isn t efficient  Then I learned that retrieving an array isn t straight forward  I realized that if you re storing more than a few strings or booleans  NSUserDefaults really isn t ideal    It s also not scalable  If you re learning how to code  learn the scalable way  Only use NSUserDefaults for storing simple strings or booleans related to preferences  Store arrays and other data using Core Data  it s not as hard as they say  Just start small   Update  Also  if you add Apple Watch support  there s another potential consideration  Your app s NSUserDefaults is now automatically sent to the Watch Extension    Using Core Data  So I ignored the warnings about Core Data being a more difficult solution and started reading  Within three hours I had it working  I had my table array being saved in Core Data and reloading the data upon opening the app back up  The tutorial code was easy enough to adapt and I was able to have it store both title and detail arrays with only a little extra experimenting    So for anyone reading this post who s struggling with NSUserDefault type issues or whose need is more than storing strings  consider spending an hour or two playing with core data   Here s the tutorial I read   http   www raywenderlich com 85578 first-core-data-app-using-swift  If you didn t check  Core Data    If you didn t check  Core Data when you created your app  you can add it after and it only takes five minutes   http   craig24 com 2014 12 how-to-add-core-data-to-an-existing-swift-project-in-xcode   http   blog zeityer com post 119012600864 adding-core-data-to-an-existing-swift-project  How to Delete from Core Data Lists  Delete Data from Coredata Swift

[ios] How to save local data in a Swift app?

Swift 3.0, 4.0 & 5.0

Swift 2.0

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