properties.swift

class Properties{
    static let sharedInstance = Properties()
    private let userDefaults:UserDefaults = UserDefaults()

    var fontSize:Double = 10.0{
        didSet{
            userDefaults.setValue(fontSize, forKey: "FONT_SIZE")
            userDefaults.synchronize()
            print("Font Size Saved")
        }
    }
}

let properties = Properties.sharedInstance