UserDefaultPropertyWrapper for Playground

UserDefaultPropertyWrapper_Playground.swift

import UIKit

// UserDefaults

extension UserDefaults {
    public func value<Value : UserDefaultCompatible>(type: Value.Type = Value.self, forKey key: String, default defaultValue: Value) -> Value {
        guard let object = object(forKey: key) else { return defaultValue }
        return Value(userDefaultObject: object) ?? defaultValue
    }
    public func setValue<Value : UserDefaultCompatible>(_ value: Value, forKey key: String) {
        set(value.toUserDefaultObject(), forKey: key)
    }
}

// UserDefaultsに保存可能な値

public protocol UserDefaultCompatible {
    init?(userDefaultObject: Any)
    func toUserDefaultObject() -> Any?
}

extension UserDefaultCompatible where Self : Codable {
    public init?(userDefaultObject: Any) {
        guard let data = userDefaultObject as? Data else { return nil }
        do {
            self = try JSONDecoder().decode(Self.self, from: data)
        } catch {
            return nil
        }
    }
    public func toUserDefaultObject() -> Any? {
        try? JSONEncoder().encode(self)
    }
}

extension UserDefaultCompatible where Self : NSObject, Self : NSCoding {
    public init?(userDefaultObject: Any) {
        guard let data = userDefaultObject as? Data else { return nil }
        if let value = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? Self {
            self = value
        } else {
            return nil
        }
    }
    public func toUserDefaultObject() -> Any? {
        if let object = try? NSKeyedArchiver.archivedData(withRootObject: self, requiringSecureCoding: false) {
            return object
        } else {
            return nil
        }
    }
}

extension Array : UserDefaultCompatible where Element : UserDefaultCompatible {
    private struct UserDefaultCompatibleError : Error {}
    public init?(userDefaultObject: Any) {
        guard let objects = userDefaultObject as? [Any] else { return nil }
        do {
            let values = try objects.map { (object: Any) -> Element in
                if let element = Element(userDefaultObject: object) {
                    return element
                } else {
                    throw UserDefaultCompatibleError()
                }
            }
            self = values
        } catch {
            return nil
        }
    }
    public func toUserDefaultObject() -> Any? {
        map { $0.toUserDefaultObject() }
    }
}

extension Dictionary : UserDefaultCompatible where Key == String, Value : UserDefaultCompatible {
    private struct UserDefaultCompatibleError : Swift.Error {}
    public init?(userDefaultObject: Any) {
        guard let objects = userDefaultObject as? [String: Any] else { return nil }
        do {
            let values = try objects.mapValues { object -> Value in
                if let value = Value(userDefaultObject: object) {
                    return value
                } else {
                    throw UserDefaultCompatibleError()
                }
            }
            self = values
        } catch {
            return nil
        }
    }

    public func toUserDefaultObject() -> Any? {
        mapValues { $0.toUserDefaultObject() }
    }
}

extension Optional : UserDefaultCompatible where Wrapped : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        self = Wrapped(userDefaultObject: userDefaultObject)
    }
    public func toUserDefaultObject() -> Any? {
        flatMap { $0.toUserDefaultObject() }
    }
}

extension Int : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension Double : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension Float : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension Bool : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension String : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension URL : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Data else { return nil }
        guard let url = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(userDefaultObject) as? URL else { return nil }
        self = url
    }
    public func toUserDefaultObject() -> Any? {
        try? NSKeyedArchiver.archivedData(withRootObject: self, requiringSecureCoding: false)
    }
}

extension Date : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

extension Data : UserDefaultCompatible {
    public init?(userDefaultObject: Any) {
        guard let userDefaultObject = userDefaultObject as? Self else { return nil }
        self = userDefaultObject
    }
    public func toUserDefaultObject() -> Any? {
        self
    }
}

// Property Wrapper

@propertyWrapper
public struct UserDefault<Value : UserDefaultCompatible> {
    private let key: String
    private let defaultValue: Value

    public init(_ key: String, default defaultValue: Value) {
        self.key = key
        self.defaultValue = defaultValue
    }

    public var wrappedValue: Value {
        get {
            UserDefaults.standard.value(type: Value.self, forKey: key, default: defaultValue)
        }
        set {
            UserDefaults.standard.setValue(newValue, forKey: key)
        }
    }
}

// Test Code

struct User : Codable, UserDefaultCompatible {
    var name: String
}

class Record : NSObject, NSCoding, UserDefaultCompatible {
    var name: String? = "abc"

    init(name: String?) {
        self.name = name
    }
    required init?(coder: NSCoder) {
        name = coder.decodeObject(forKey: "name") as? String
    }

    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
    }
}

struct Settings {

    @UserDefault("user", default: User(name: "abc"))
    var user: User

    @UserDefault("userOptional", default: nil)
    var userOptional: User?

    @UserDefault("users", default: [])
    var users: [User]

    @UserDefault("userArrayOptional", default: nil)
    var userArrayOptional: [User]?

    @UserDefault("userDictionary", default: [:])
    var userDictionary: [String: User]

    @UserDefault("userDictionaryOptional", default: nil)
    var userDictionaryOptional: [String: User]?

    @UserDefault("int", default: 5)
    var int: Int

    @UserDefault("intOptional", default: nil)
    var intOptional: Int?

    @UserDefault("doubleValue", default: 23.56)
    var doubleValue: Double

    @UserDefault("doubleValueOptional", default: nil)
    var doubleValueOptional: Double?

    @UserDefault("floatValue", default: 1.23)
    var floatValue: Float

    @UserDefault("floatValueOptional", default: nil)
    var floatValueOptional: Float?

    @UserDefault("bool", default: true)
    var bool: Bool

    @UserDefault("boolOptional", default: nil)
    var boolOptional: Bool?

    @UserDefault("string", default: "defaultString")
    var string: String

    @UserDefault("stringOptional", default: nil)
    var stringOptional: String?

    @UserDefault("url", default: URL(string: "https://google.com")!)
    var url: URL

    @UserDefault("urlOptional", default: nil)
    var urlOptional: URL?

    @UserDefault("date", default: Date(timeIntervalSinceReferenceDate: 0))
    var date: Date

    @UserDefault("dateOptional", default: nil)
    var dateOptional: Date?

    @UserDefault("data", default: Data())
    var data: Data

    @UserDefault("dataOptional", default: nil)
    var dataOptional: Data?

    @UserDefault("record", default: Record(name: "default record name"))
    var record: Record

    @UserDefault("recordOptional", default: nil)
    var recordOptional: Record?

}

let keys = UserDefaults.standard.dictionaryRepresentation().keys
keys.forEach(UserDefaults.standard.removeObject(forKey:))

var settings = Settings()

settings.user
settings.user = User(name: "change name")
settings.user
settings.userOptional
settings.userOptional = User(name: "optional user")
settings.userOptional
settings.users
settings.users = [User(name: "change name")]
settings.users
settings.userArrayOptional
settings.userArrayOptional = [User(name: "change name")]
settings.userArrayOptional
settings.userDictionary
settings.userDictionary = ["key": User(name: "change name")]
settings.userDictionary
settings.userDictionaryOptional
settings.userDictionaryOptional = ["key": User(name: "change name")]
settings.userDictionaryOptional
settings.int
settings.int = 432
settings.int
settings.intOptional
settings.intOptional = 543
settings.intOptional
settings.doubleValue
settings.doubleValue = 5.68
settings.doubleValue
settings.doubleValueOptional
settings.doubleValueOptional = 111.3
settings.doubleValueOptional
settings.floatValue
settings.floatValue = 99.99
settings.floatValue
settings.floatValueOptional
settings.floatValueOptional = -32
settings.floatValueOptional
settings.bool
settings.bool = false
settings.bool
settings.boolOptional
settings.boolOptional = true
settings.boolOptional
settings.string
settings.string = "string"
settings.string
settings.stringOptional
settings.stringOptional = "optional string"
settings.stringOptional
settings.url
settings.url = URL(string: "https://yahoo.co.jp")!
settings.url
settings.urlOptional
settings.urlOptional = URL(string: "https://yahoo.co.jp")
settings.urlOptional
settings.date
settings.date = Date(timeIntervalSinceReferenceDate: 3600)
settings.date
settings.dateOptional
settings.dateOptional = Date(timeIntervalSinceReferenceDate: 7200)
settings.dateOptional
settings.data
settings.data = Data(base64Encoded: "1234")!
settings.data
settings.dataOptional
settings.dataOptional = Data(base64Encoded: "1234")!
settings.dataOptional
settings.record
settings.record = Record(name: "change name")
settings.record
settings.recordOptional
settings.recordOptional = Record(name: "change name")
settings.recordOptional