I have a class that saves the state of something, in my case some variable of the ViewController, but sometimes it loads wrong or old data, but I can't figure out why.
Maybe somebody can have a look of my code and see if it makes sense.
class TopFlopState: Codable, PersistenceState {
var group: Groups = .large {
didSet {
save()
}
}
var base: Bases = .usd {
didSet {
save()
}
}
var valueOne: StatIntervalBaseModel = StatIntervalBaseModel(stat: "ppc", interval: "24h", base: "usd") {
didSet {
save()
}
}
init(){
let savedValues = load()
if savedValues != nil {
self.group = savedValues!.group
self.base = savedValues!.base
self.valueOne = savedValues!.valueOne
}
}
}
This is the PersistenceState protocol:
/**
Saves and Loads the class, enum etc. with UserDefaults.
Has to conform to Codable.
Uses as Key, the name of the class, enum etc.
*/
protocol PersistenceState {
}
extension PersistenceState where Self: Codable {
private var keyUserDefaults: String {
return String(describing: self)
}
func save() {
saveUserDefaults(withKey: keyUserDefaults, myType: self)
}
func load() -> Self? {
return loadUserDefaults(withKey: keyUserDefaults)
}
private func saveUserDefaults<T: Codable>(withKey key: String, myType: T){
do {
let data = try PropertyListEncoder().encode(myType)
UserDefaults.standard.set(data, forKey: key)
print("Saved for Key:", key)
} catch {
print("Save Failed")
}
}
private func loadUserDefaults<T: Codable>(withKey key: String) -> T? {
guard let data = UserDefaults.standard.object(forKey: key) as? Data else { return nil }
do {
let decoded = try PropertyListDecoder().decode(T.self, from: data)
return decoded
} catch {
print("Decoding failed for key", key)
return nil
}
}
}
If a value gets set to the value it should automatically save, but like I set sometimes it saves the right values but loads the wrong ones...
In my opinion, It return the cache. Because in Apple official documentation, it state
UserDefaults caches the information to avoid having to open the user’s defaults database each time you need a default value
Maybe you can change the flow, when to save the data. In your code show that you call save() 3 times in init().
Related
i have been trying to make that when a user adds a page to favorites or removes the page it saves it, so when a user closes the app it remembers it. I can't figure out how i can save the mushrooms table. I want to save it locally and is it done by using Prospects ?
class Favorites: ObservableObject {
public var mushrooms: Set<String>
public let saveKey = "Favorites"
init() {
mushrooms = []
}
func contains(_ mushroom: Mushroom) -> Bool {
mushrooms.contains(mushroom.id)
}
func add (_ mushroom: Mushroom) {
objectWillChange.send()
mushrooms.insert(mushroom.id)
save()
}
func remove(_ mushroom: Mushroom) {
objectWillChange.send()
mushrooms.remove(mushroom.id)
save()
}
func save() {
}
}
I was able to figure it out. Here is the code i did if someone else is struggling with this.
I added this to the save function
func save() {
let encoder = JSONEncoder()
if let encoded = try? encoder.encode(mushrooms) {
defaults.set(encoded, forKey: "Favorites")
}
}
And to the init() :
let decoder = JSONDecoder()
if let data = defaults.data(forKey: "Favorites") {
let mushroomData = try? decoder.decode(Set<String>.self, from: data)
self.mushrooms = mushroomData ?? []
} else {
self.mushrooms = []
}
EDIT:
and of course add the defaults
let defaults = UserDefaults.standard
Apologies for the stupid question, I'm still really new to the Swift language.
Following up on this answer by #matt, I want to combine these two statements into a single var
UserDefaults.standard.set(try? PropertyListEncoder().encode(songs), forKey:"songs")
if let data = UserDefaults.standard.value(forKey:"songs") as? Data {
let songs2 = try? PropertyListDecoder().decode(Array<Song>.self, from: data)
}
I've thought maybe using a var with didSet {} like something along the lines of
var test: Array = UserDefaults.standard. { // ??
didSet {
UserDefaults.standard.set(try? PropertyListEncoder().encode(test), forKey: "songs")
}
}
But I can't think of where to go from here.
Thanks for the help in advance :))
The property should not be a stored property. It should be a computed property, with get and set accessors:
var songsFromUserDefaults: [Song]? {
get {
if let data = UserDefaults.standard.value(forKey:"songs") as? Data {
return try? PropertyListDecoder().decode(Array<Song>.self, from: data)
} else {
return nil
}
}
set {
if let val = newValue {
UserDefaults.standard.set(try? PropertyListEncoder().encode(val), forKey:"songs")
}
}
}
Notice that since the decoding can fail, the getter returns an optional. This forces the setter to accept an optional newValue, and I have decided to only update UserDefaults when the value is not nil. Another design is to use try! when decoding, or return an empty array when the decoding fails. This way the type of the property can be non-optional, and the nil-check in the setter can be removed.
While you can use computed properties like Sweeper suggested (+1), I might consider putting this logic in a property wrapper.
In SwiftUI you can use AppStorage. Or you can roll your own. Here is a simplified example:
#propertyWrapper public struct Saved<Value: Codable> {
private let key: String
public var wrappedValue: Value? {
get {
guard let data = UserDefaults.standard.data(forKey: key) else { return nil }
return (try? JSONDecoder().decode(Value.self, from: data))
}
set {
guard
let value = newValue,
let data = try? JSONEncoder().encode(value)
else {
UserDefaults.standard.removeObject(forKey: key)
return
}
UserDefaults.standard.set(data, forKey: key)
}
}
init(key: String) {
self.key = key
}
}
And then you can do things like:
#Saved(key: "username") var username: String?
Or
#Saved(key: "songs") var songs: [Song]?
In my app, in a few places I am loading data from Firebase Firestore database and showing the data. The problem is I am not adopting the DRY technique and I know I shouldn't, but I am reusing this same load function in different places in my app.
func loadData() {
let user = Auth.auth().currentUser
db.collection("users").document((user?.uid)!).collection("children").getDocuments() {
QuerySnapshot, error in
if let error = error {
print("\(error.localizedDescription)")
} else {
// get all children into an array
self.childArray = QuerySnapshot!.documents.flatMap({Child(dictionary: $0.data())})
DispatchQueue.main.async {
self.childrenTableView.reloadData()
}
}
}
}
The function simply grabs all the children from the database and adds them to my child array.
Is there some better way to do this or a central place I can put this function where it can be called as and when I need it in the app instead of repeatedly adding it in multiple view controllers?
I thought about a helper class, and just calling the function, but then not sure how to add the result to the childArray in the viewcontroller I needed it?
my Child model
import UIKit
import FirebaseFirestore
protocol DocumentSerializable {
init?(dictionary:[String:Any])
}
// Child Struct
struct Child {
var name: String
var age: Int
var timestamp: Date
var imageURL: String
var dictionary:[String:Any] {
return [
"name":name,
"age":age,
"timestamp":timestamp,
"imageURL":imageURL
]
}
}
//Child Extension
extension Child : DocumentSerializable {
init?(dictionary: [String : Any]) {
guard let name = dictionary["name"] as? String,
let age = dictionary["age"] as? Int,
let imageURL = dictionary["imageURL"] as? String,
let timestamp = dictionary["timestamp"] as? Date else {
return nil
}
self.init(name: name, age: age, timestamp: timestamp, imageURL: imageURL)
}
}
EDIT: I have updated to safely unwrap the optionals. You may still have to modify as I am not sure what your Firebase structure is, nor do I know your Child initializer.
You could just write this as a static function and then reuse it everywhere. I assume you might have some class related to whatever "children" is, and that'd be the best place to implement. You could pass the results (as an option array of Child) in a completion handler so that you can do whatever you need with those results. It'd look something like this:
static func loadData(_ completion: (_ children: [Child]?)->()) {
guard let user = Auth.auth().currentUser else { completion(nil); return }
Firestore.firestore().collection("users").document(user.uid).collection("children").getDocuments() {
querySnapshot, error in
if let error = error {
print("\(error.localizedDescription)")
completion(nil)
} else {
guard let snapshot = querySnapshot else { completion(nil); return }
// get all children into an array
let children = snapshot.documents.flatMap({Child(dictionary: $0.data())})
completion(children)
}
}
}
Assuming you have this implemented in your Child class you would use it like this:
Child.loadData { (children) in
DispatchQueue.main.async {
if let loadedChildren = children {
//Do whatever you need with the children
self.childArray = loadedChildren
}
}
}
I'm designing a data manager for my Core Data model and I'd like to create a generic function to fetch relatives of a class.
I’ve created a protocol allowing to build managers for each data type. In this protocol I already defined two associated types T and K and several simple functions. Now I’m stuck with a class relatives fetching method — I need to indicate somehow that T has K relatives. I’ve tried in vain to create some protocol indicating this relationship thru mutual properties, so both classes could conform to this protocol. Any idea, is it even possible?
import Foundation
import CoreData
protocol DataManager {
associatedtype T: NSManagedObject, NSFetchRequestResult
associatedtype K: NSManagedObject, NSFetchRequestResult // Relative
static var sharedInstance: Self { get }
static func getAll(sorted: [NSSortDescriptor]?, context: NSManagedObjectContext) -> [T]?
static func insert(item: T)
static func update(item: T)
static func clean()
static func deleteById(id: String)
// Relatives
static func getRelatives(by: T) -> [K]?
static func get(byRelative: K) -> [T]?
}
extension DataManager {
static func getAll(sorted: [NSSortDescriptor]?, context: NSManagedObjectContext) -> [T]? {
guard let fetchRequest: NSFetchRequest<T> = T.fetchRequest() as? NSFetchRequest<T> else { return nil }
fetchRequest.sortDescriptors = sorted
var results: [T]? = nil
do {
results = try context.fetch(fetchRequest)
} catch {
assert(false, error.localizedDescription)
} //TODO: Handle Errors
return results
}
}
protocol Identifiable {
typealias Identity = String
var id: Identity? { get }
}
extension DataManager where Self.T: Identifiable {
static func get(by id: T.Identity, context: NSManagedObjectContext) -> T? {
guard let fetchRequest: NSFetchRequest<T> = T.fetchRequest() as? NSFetchRequest<T> else { return nil }
fetchRequest.predicate = NSPredicate(format: "%K == %#", "id", id)
var rawResults: [T]? = nil
do {
rawResults = try context.fetch(fetchRequest)
} catch {
assert(false, error.localizedDescription)
} //TODO: Handle Errors
if let result = rawResults?.first {
return result }
else { return nil }
}
}
Well, I've created one solution.
We can identify all relations with a particular class:
let relationships = T.entity().relationships(forDestination: K.entity())
It allows us to find all IDs of an item for each relationship (we can have many relationships for the same relative Entity):
let relativesIDs = item.objectIDs(forRelationshipNamed: relationship.name)
So, we can use these IDs to fetch records from another class.
static func getRelatives(of item: T, context:NSManagedObjectContext) -> [K]? {
guard let fetchRequest: NSFetchRequest<K> = K.fetchRequest() as? NSFetchRequest<K> else { return nil }
fetchRequest.fetchBatchSize = 100
var results: [K]? = nil
var resultSet: Set<K> = [] // doesn't allow duplicates
let relationships = T.entity().relationships(forDestination: K.entity())
for relationship in relationships {
let relativesIDs = item.objectIDs(forRelationshipNamed: relationship.name)
let predicate = NSPredicate(format: "self IN %#", relativesIDs)
fetchRequest.predicate = predicate
var batchResults: [K] = []
do {
batchResults = try context.fetch(fetchRequest)
} catch {
assert(false, error.localizedDescription)
} //TODO: Handle Errors
if batchResults.count > 0 { resultSet = resultSet.union(Set(batchResults)) }
}
if resultSet.count > 0 { results = Array(resultSet) }
return results
}
I'm not sure that this is the most elegant solution, but it works :-)
I have an enum like this:
enum Environment {
case Production
case Staging
case Dev
}
And I'd like to save an instance in NSUserDefaults like this:
func saveEnvironment(environment : Environment){
NSUserDefaults.standardUserDefaults().setObject(environment, forKey: kSavedEnvironmentDefaultsKey)
}
I understand that a Swift enum isn't an NSObject, and that makes it difficult to save, but I'm unsure what the best way is to convert it to something storable.
Using rawValue for the enum is one way of using types that can be stored in NSUserDefaults, define your enum to use a rawValue. Raw values can be strings, characters, or any of the integer or floating-point number types :
enum Environment: String {
case Production = "Prod"
case Staging = "Stg"
case Dev = "Dev"
}
You can also create an enum instance directly using the rawValue (which could come from NSUserDefaults) like:
let env = Environment(rawValue: "Dev")
You can extract the rawValue (String) from the enum object like this and then store it in NSUserDefaults if needed:
if let myEnv = env {
println(myEnv.rawValue)
}
func saveEnvironment(environment : Environment){
NSUserDefaults.standardUserDefaults().setObject(environment.rawValue, forKey: kSavedEnvironmentDefaultsKey)
}
If you would like to save/read data from UserDefaults and separate some logic, you can do it in following way (Swift 3):
enum Environment: String {
case Production
case Staging
case Dev
}
class UserDefaultsManager {
static let shared = UserDefaultsManager()
var environment: Environment? {
get {
guard let environment = UserDefaults.standard.value(forKey: kSavedEnvironmentDefaultsKey) as? String else {
return nil
}
return Environment(rawValue: environment)
}
set(environment) {
UserDefaults.standard.set(environment?.rawValue, forKey: kSavedEnvironmentDefaultsKey)
}
}
}
So saving data in UserDefaults will look this way:
UserDefaultsManager.shared.environment = Environment.Production
And reading data, saved in UserDefaults in this way:
if let environment = UserDefaultsManager.shared.environment {
//you can do some magic with this variable
} else {
print("environment data not saved in UserDefaults")
}
Using Codable protocol
Extent Environment enum that conforms to Codable protocol to encode and decode values as Data.
enum Environment: String, Codable {
case Production
case Staging
case Dev
}
A wrapper for UserDefaults:
struct UserDefaultsManager {
static var userDefaults: UserDefaults = .standard
static func set<T>(_ value: T, forKey: String) where T: Encodable {
if let encoded = try? JSONEncoder().encode(value) {
userDefaults.set(encoded, forKey: forKey)
}
}
static func get<T>(forKey: String) -> T? where T: Decodable {
guard let data = userDefaults.value(forKey: forKey) as? Data,
let decodedData = try? JSONDecoder().decode(T.self, from: data)
else { return nil }
return decodedData
}
}
Usage
// Set
let environment: Environment = .Production
UserDefaultsManager.set(environment, forKey: "environment")
// Get
let environment: Environment? = UserDefaultsManager.get(forKey: "environment")
Here is another alternative that can be be easily used with enums based on types (like String, Int etc) that can be stored by NSUserDefaults.
#propertyWrapper
struct StoredProperty<T: RawRepresentable> {
let key: String
let defaultValue: T
init(_ key: String, defaultValue: T) {
self.key = key
self.defaultValue = defaultValue
}
var wrappedValue: T {
get {
guard let rawValue = UserDefaults.standard.object(forKey: key) as? T.RawValue, let value = T(rawValue: rawValue) else {
return defaultValue
}
return value
}
set {
UserDefaults.standard.set(newValue.rawValue, forKey: key)
}
}
}
Example usage:
enum Environment: String {
case Production
case Staging
case Dev
}
#StoredProperty("Environment", defaultValue: .Dev)
var storedProperty: Environment
Swift 5.1 You can create a generic property wrapper, using Codable to transform values in and out the UserDefaults
extension UserDefaults {
// let value: Value already set somewhere
// UserDefaults.standard.set(newValue, forKey: "foo")
//
func set<T>(_ value: T, forKey: String) where T: Encodable {
if let encoded = try? JSONEncoder().encode(value) {
setValue(encoded, forKey: forKey)
}
}
// let value: Value? = UserDefaults.standard.get(forKey: "foo")
//
func get<T>(forKey: String) -> T? where T: Decodable {
guard let data = value(forKey: forKey) as? Data,
let decodedData = try? JSONDecoder().decode(T.self, from: data)
else { return nil }
return decodedData
}
}
#propertyWrapper
public struct UserDefaultsBacked<Value>: Equatable where Value: Equatable, Value: Codable {
let key: String
let defaultValue: Value
var storage: UserDefaults = .standard
public init(key: String, defaultValue: Value) {
self.key = key
self.defaultValue = defaultValue
}
// if the value is nil return defaultValue
// if the value empty return defaultValue
// otherwise return the value
//
public var wrappedValue: Value {
get {
let value: Value? = storage.get(forKey: key)
if let stringValue = value as? String, stringValue.isEmpty {
// for string values we want to equate nil with empty string as well
return defaultValue
}
return value ?? defaultValue
}
set {
storage.set(newValue, forKey: key)
storage.synchronize()
}
}
}
// use it
struct AppState: Equatable {
enum TabItem: String, Codable {
case home
case book
case trips
case account
}
var isAppReady = false
#UserDefaultsBacked(key: "selectedTab", defaultValue: TabItem.home)
var selectedTab
// default value will be TabItem.home
#UserDefaultsBacked(key: "selectedIndex", defaultValue: 33)
var selectedIndex
// default value will be 33
}
I am using like this type staging. Can you please try this it will help you.
enum Environment: String {
case Production = "Production URL"
case Testing = "Testing URl"
case Development = "Development URL"
}
//your button actions
// MARK: set Development api
#IBAction func didTapDevelopmentAction(_ sender: Any) {
let env = Environment.Development.rawValue
print(env)
UserDefaults.standard.set(env, forKey:Key.UserDefaults.stagingURL)
}
// MARK: set Production api
#IBAction func didTapProductionAction(_ sender: Any) {
let env = Environment.Production.rawValue
print(env)
UserDefaults.standard.set(env, forKey:Key.UserDefaults.stagingURL)
}
// MARK: set Testing api
#IBAction func didTapTestingAction(_ sender: Any) {
let env = Environment.Testing.rawValue
print(env)
UserDefaults.standard.set(env, forKey:Key.UserDefaults.stagingURL)
}
//Based on selection act
print("\(UserDefaults.standard.object(forKey: "stagingURL") ?? "")")
Swift 5.1
You can create property wrapper for this
#propertyWrapper final class UserDefaultsLanguageValue {
var defaultValue: LanguageType
var key: UserDefaultsKey
init(key: UserDefaultsKey, defaultValue: LanguageType) {
self.key = key
self.defaultValue = defaultValue
}
var wrappedValue: LanguageType {
get { LanguageType(rawValue: UserDefaults.standard.object(forKey: key.rawValue) as? String ?? defaultValue.rawValue) ?? .en }
set { UserDefaults.standard.set(newValue.rawValue, forKey: key.rawValue) }
}
}
enum UserDefaultsKey: String {
case language
}
enum LanguageType: String {
case en
case ar
}
And use it just like that
#UserDefaultsLanguageValue(key: .language, defaultValue: LanguageType.en) var language