UserDefaults+Key.swift

import Foundation


extension UserDefaults {
	struct Key {
		typealias RawValue = String
		let rawValue: RawValue
		init(_ string: String) {
			self.rawValue = string
		}
	}

	func value<Value>(forKey key: Key) -> Value? {
		value(forKey: key.rawValue) as? Value
	}

	func set<Value>(value: Value, forKey key: Key) {
		set(value, forKey: key.rawValue)
	}

	// One could also add overloads for the standard types...
	func bool(forKey key: Key) -> Bool {
		bool(forKey: key.rawValue)
	}
}

extension UserDefaults.Key: ExpressibleByStringLiteral {
	init(stringLiteral: String) {
		self.init(stringLiteral)
	}
}

extension UserDefaults.Key {
	static let isFooEnabledKey: Self = "isFooEnabledKey"
}

let defaults = UserDefaults.standard
var value = defaults.bool(forKey: .isFooEnabledKey)
print("initialvalue: \(value)")
defaults.set(value: true, forKey: .isFooEnabledKey)
value = defaults.bool(forKey: .isFooEnabledKey)
print("currentValue: \(value)")
defaults.set(value: false, forKey: .isFooEnabledKey)
value = defaults.bool(forKey: .isFooEnabledKey)
print("currentValue: \(value)")