Property cannot be marked @objc because its type cannot be represented in Objective-C

You can create a class that represents your tuple.

Code:

class Time: NSObject {
    let hours: Int
    let minutes: Int
    let seconds: Int

    init(hours: Int, minutes: Int, seconds: Int) {
        self.hours = hours
        self.minutes = minutes
        self.seconds = seconds
    }
}

@objc open var remainingTime: Time?