optional_chaining.swift

class TransportStorage {
    
    var output: NSObject!
    
    let database: Any // <----- Constant
    var token: String?
    
    init(database: Any) {
        self.database = database
    }
    
}

let storage = TransportStorage(database: UserDefaults.standard)

// Optional with case .none -> nil
storage.token?.description

// this triggers a runtime error
storage.token!.description

storage.token = UUID().uuidString

// Optional with case .some -> String
storage.token?.description

// *** Crash!!! The output in currently nil ***
// this triggers a runtime error
//  storage.output.description

storage.output = NSObject()

// Output have with value. All work good
storage.output.description