问题

How can I use UserDefaults to save/retrieve strings, booleans and other data in Swift?

回答1:

ref: NSUserdefault objectTypes

Swift 3 and above

Store

UserDefaults.standard.set(true, forKey: "Key") //Bool
UserDefaults.standard.set(1, forKey: "Key")  //Integer
UserDefaults.standard.set("TEST", forKey: "Key") //setObject

Retrieve

 UserDefaults.standard.bool(forKey: "Key")
 UserDefaults.standard.integer(forKey: "Key")
 UserDefaults.standard.string(forKey: "Key")

Remove

 UserDefaults.standard.removeObject(forKey: "Key")

Remove all Keys

 if let appDomain = Bundle.main.bundleIdentifier {
UserDefaults.standard.removePersistentDomain(forName: appDomain)
 }

Swift 2 and below

Store

NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "yourkey")
NSUserDefaults.standardUserDefaults().synchronize()

Retrieve

  var returnValue: [NSString]? = NSUserDefaults.standardUserDefaults().objectForKey("yourkey") as? [NSString]

Remove

 NSUserDefaults.standardUserDefaults().removeObjectForKey("yourkey")

Register

registerDefaults: adds the registrationDictionary to the last item in every search list. This means that after NSUserDefaults has looked for a value in every other valid location, it will look in registered defaults, making them useful as a "fallback" value. Registered defaults are never stored between runs of an application, and are visible only to the application that registers them.

Default values from Defaults Configuration Files will automatically be registered.

for example detect the app from launch , create the struct for save launch

struct DetectLaunch {
static let keyforLaunch = "validateFirstlunch"
static var isFirst: Bool {
    get {
        return UserDefaults.standard.bool(forKey: keyforLaunch)
    }
    set {
        UserDefaults.standard.set(newValue, forKey: keyforLaunch)
    }
}
}

UserDefaults.standard.register(defaults: [
        DetectLaunch.isFirst: true
    ])

remove the value on app termination:

func applicationWillTerminate(_ application: UIApplication) {
    DetectLaunch.isFirst = false

}

and check the condition as

if DetectLaunch.isFirst {
  // app launched from first
}

UserDefaults suite name

another one property suite name, mostly its used for App Groups concept, the example scenario I taken from here :

The use case is that I want to separate my UserDefaults (different business logic may require Userdefaults to be grouped separately) by an identifier just like Android's SharedPreferences. For example, when a user in my app clicks on logout button, I would want to clear his account related defaults but not location of the the device.

let user = UserDefaults(suiteName:"User")

use of userDefaults synchronize, the detail info has added in the duplicate answer.

回答2:

Best way to use UserDefaults

Steps

Create extension of UserDefaults
Create enum with required Keys to store in local
Store and retrieve the local data wherever you want

Sample

extension UserDefaults{

    //MARK: Check Login
    func setLoggedIn(value: Bool) {
        set(value, forKey: UserDefaultsKeys.isLoggedIn.rawValue)
        //synchronize()
    }

    func isLoggedIn()-> Bool {
        return bool(forKey: UserDefaultsKeys.isLoggedIn.rawValue)
    }

    //MARK: Save User Data
    func setUserID(value: Int){
        set(value, forKey: UserDefaultsKeys.userID.rawValue)
        //synchronize()
    }

    //MARK: Retrieve User Data
    func getUserID() -> Int{
        return integer(forKey: UserDefaultsKeys.userID.rawValue)
    }
}

enum for Keys used to store data

enum UserDefaultsKeys : String {
    case isLoggedIn
    case userID
}

Save in UserDefaults where you want

UserDefaults.standard.setLoggedIn(value: true)          // String
UserDefaults.standard.setUserID(value: result.User.id!) // String

Retrieve data anywhere in app

print("ID : \(UserDefaults.standard.getUserID())")
UserDefaults.standard.getUserID()

Remove Values

UserDefaults.standard.removeObject(forKey: UserDefaultsKeys.userID)

This way you can store primitive data in best

Update You need no use synchronize() to store the values. As @Moritz pointed out the it unnecessary and given the article about it.Check comments for more detail

回答3:

Swift 4 :

Store

    UserDefaults.standard.set(object/value, forKey: "key_name")

Retrive

    var returnValue: [datatype]? = UserDefaults.standard.object(forKey: "key_name") as? [datatype]

Remove

    UserDefaults.standard.removeObject(forKey:"key_name")

回答4:

//Save
NSUserDefaults.standardUserDefaults().setObject("yourString", forKey: "YourStringKey")

//retrive
let yourStr : AnyObject? = NSUserDefaults.standardUserDefaults().objectForKey("YourStringKey")

回答5:

You can use NSUserDefaults in swift this way,

@IBAction func writeButton(sender: UIButton)
{
    let defaults = NSUserDefaults.standardUserDefaults()
    defaults.setObject("defaultvalue", forKey: "userNameKey")

}

@IBAction func readButton(sender: UIButton)
{
    let defaults = NSUserDefaults.standardUserDefaults()
    let name = defaults.stringForKey("userNameKey")
    println(name) //Prints defaultvalue in console
}

回答6:

Swift 5 and above:

let defaults = UserDefaults.standard

defaults.set(25, forKey: "Age")
let savedInteger = defaults.integer(forKey: "Age")

defaults.set(true, forKey: "UseFaceID")
let savedBoolean = defaults.bool(forKey: "UseFaceID")

defaults.set(CGFloat.pi, forKey: "Pi")
defaults.set("Your Name", forKey: "Name")
defaults.set(Date(), forKey: "LastRun")


let array = ["Hello", "World"]
defaults.set(array, forKey: "SavedArray")


let savedArray = defaults.object(forKey: "SavedArray") as? [String] ?? [String()

let dict = ["Name": "Your", "Country": "YourCountry"]
defaults.set(dict, forKey: "SavedDict")

let savedDictionary = defaults.object(forKey: "SavedDictionary") as? [String: String] ?? [String: String]()

回答7:

I saved NSDictionary normally and able to get it correctly.

 dictForaddress = placemark.addressDictionary! as NSDictionary
        let userDefaults = UserDefaults.standard
        userDefaults.set(dictForaddress, forKey:Constants.kAddressOfUser)

// For getting data from NSDictionary.

let userDefaults = UserDefaults.standard
    let dictAddress = userDefaults.object(forKey: Constants.kAddressOfUser) as! NSDictionary

回答8:

In class A, set value for key:

let text = "hai"  
UserDefaults.standard.setValue(text, forKey: "textValue")

In class B, get the value for the text using the key which declared in class A and assign it to respective variable which you need:

var valueOfText  = UserDefaults.value(forKey: "textValue")

回答9:

Swift 4, I have used Enum for handling UserDefaults.

This is just a sample code. You can customize it as per your requirements.

For Storing, Retrieving, Removing. In this way just add a key for your UserDefaults key to the enum. Handle values while getting and storing according to dataType and your requirements.

enum UserDefaultsConstant : String {
    case AuthToken, FcmToken

    static let defaults = UserDefaults.standard


   //Store
    func setValue(value : Any) {
        switch self {
        case .AuthToken,.FcmToken:
            if let _ = value as? String {
                UserDefaults.standard.set(value, forKey: self.rawValue)
            }
            break
        }

        UserDefaults.standard.synchronize()
    }

   //Retrieve
    func getValue() -> Any? {
        switch self {
        case .AuthToken:
            if(UserDefaults.standard.value(forKey: UserDefaultsConstant.AuthToken.rawValue) != nil) {

                return "Bearer "+(UserDefaults.standard.value(forKey: UserDefaultsConstant.AuthToken.rawValue) as! String)
            }
            else {
                return ""
            }

        case .FcmToken:

            if(UserDefaults.standard.value(forKey: UserDefaultsConstant.FcmToken.rawValue) != nil) {
                print(UserDefaults.standard.value(forKey: UserDefaultsConstant.FcmToken.rawValue))
                return (UserDefaults.standard.value(forKey: UserDefaultsConstant.FcmToken.rawValue) as! String)
            }
            else {
                return ""
            }
        }
    }

    //Remove
    func removeValue() {
        UserDefaults.standard.removeObject(forKey: self.rawValue)
        UserDefaults.standard.synchronize()
    }
}

For storing a value in userdefaults,

if let authToken = resp.data?.token {
     UserDefaultsConstant.AuthToken.setValue(value: authToken)
    }

For retrieving a value from userdefaults,

//As AuthToken value is a string
    (UserDefaultsConstant.AuthToken.getValue() as! String)

回答10:

class UserDefaults_WorstPresidentName {
    static let key = "appname.worstPresidentName"

    static var value: String? {
        get {
            return UserDefaults.standard.string(forKey: key)
        }
        set {
            if newValue != nil {
                UserDefaults.standard.set(newValue, forKey: key)
            } else {
                UserDefaults.standard.removeObject(forKey: key)
            }
        }
    }
}

回答11:

I would say Anbu's answer perfectly fine but I had to add guard while fetching preferences to make my program doesn't fail

Here is the updated code snip in Swift 5

Storing data in Preferences

@IBAction func savePreferenceData(_ sender: Any) {
        print("Storing data..")
        UserDefaults.standard.set("RDC", forKey: "UserName") //String
        UserDefaults.standard.set("TestPass", forKey: "Passowrd")  //String
        UserDefaults.standard.set(21, forKey: "Age")  //Integer

    }

Fetching data from Preferences

    @IBAction func fetchPreferenceData(_ sender: Any) {
        print("Fetching data..")

        //added guard
        guard let uName = UserDefaults.standard.string(forKey: "UserName") else { return }
        print("User Name is :"+uName)
        print(UserDefaults.standard.integer(forKey: "Age"))
    }

回答12:

UserDefault+Helper.swift

import UIKit

private enum Defaults: String {
   case countryCode = "countryCode"
   case userloginId   = "userloginid"
}

final class UserDefaultHelper {

static var countryCode: String? {
    set{
        _set(value: newValue, key: .countryCode)
    } get {
        return _get(valueForKay: .countryCode) as? String ?? ""
    }
}

static var userloginId: String? {
    set{
        _set(value: newValue, key: .userloginId)
    } get {
        return _get(valueForKay: .userloginId) as? String ?? ""
    }
}

private static func _set(value: Any?, key: Defaults) {
    UserDefaults.standard.set(value, forKey: key.rawValue)
}

private static func _get(valueForKay key: Defaults)-> Any? {
    return UserDefaults.standard.value(forKey: key.rawValue)
}

static func deleteCountryCode() {
    UserDefaults.standard.removeObject(forKey: Defaults.countryCode.rawValue)
 }

static func deleteUserLoginId() {
    UserDefaults.standard.removeObject(forKey: Defaults.userloginId.rawValue)
 }
}

Usage:

Save Value:

UserDefaultHelper.userloginId = data["user_id"] as? String

Fetch Value:

let userloginid = UserDefaultHelper.userloginId

Delete Value:

UserDefaultHelper.deleteUserLoginId()

来源：https://stackoverflow.com/questions/31203241/how-can-i-use-userdefaults-in-swift

标签

ios

swift

nsuserdefaults

userdefaults

How can I use UserDefaults in Swift?

问题

回答1:

Swift 3 and above

Swift 2 and below

UserDefaults suite name

回答2:

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回答4:

回答5:

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回答11:

回答12: