gist.swift

class UDvars {
    
    var AppLaunch: Int = UserDefaults.standard.object(forKey: "AppLaunch") as? Int ?? 0 {
        didSet {
            UserDefaults.standard.set(AppLaunch, forKey: "AppLaunch")
        }
    }
    
    var Bool: Bool = UserDefaults.standard.object(forKey: "Bool") as? Bool ?? false {
        didSet {
            UserDefaults.standard.set(Bool, forKey: "Bool")
        }
    }
    
    var String: String = UserDefaults.standard.object(forKey: "String") as? String ?? "" {
        didSet {
            UserDefaults.standard.set(String, forKey: "String")
        }
    }
    
}

let GlobalVars = UDvars()

synchronize is not necessary now. See release notes and header, that mentions that.