在通知标题中显示功能的结果（Swift 3，iOS10）

我正在ios10中从我的Swift 3应用程序触发本地通知，虽然我可以使通知正常运行，但我正在尝试将变量（恰好是从函数返回的值）传递为通知的标题。与其显示该变量的内容，不如将其显示为“（功能）”。

我在应用程序本身中使用了与标签文本相同的变量，没有任何问题。

我创建了以下类和类函数来安排通知：

class notificationController {

class func scheduleNotification(at date: Date, header: String, body: String) {

    let calendar = Calendar(identifier: .gregorian)
    let components = calendar.dateComponents(in: .current, from: date)
    let newComponents = DateComponents(calendar: calendar, timeZone: .current, month: components.month, day: components.day, hour: components.hour, minute: components.minute)

    let trigger = UNCalendarNotificationTrigger(dateMatching: newComponents, repeats: false)

    let content = UNMutableNotificationContent()
    content.title = NSString.localizedUserNotificationString(forKey: header, arguments: nil)
    content.body = body
    content.sound = UNNotificationSound.default()

    let request = UNNotificationRequest(identifier: "textNotification", content: content, trigger: trigger)

    UNUserNotificationCenter.current().removeAllPendingNotificationRequests()
    UNUserNotificationCenter.current().add(request) {(error) in
        if let error = error {
            print("error: \(error)")
        }
    }


}

然后viewdidload()，在与主屏幕关联的视图控制器的函数中定义要传递给此函数的变量，然后调用该scheduleNotification函数：

        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "dd/MM/yyyy HH:mm:ss"
        let strDate = "25/01/2017 21:21:00"
        let notificationDate = dateFormatter.date(from: strDate)
        let dayNumber = String(describing: (playerArray[0]?.calculateDays)!)
        let header = "Welcome to day \(dayNumber) of your life"
        var body : String = ""

    if(infoArray.count > 0) {
        body = (infoArray[0]?.text)!
   } else {body = "Doesn't it feel great to be alive?"}

        notificationController.scheduleNotification(at: notificationDate!, header: header, body: body)

PlayerArray是一个包含一个Player CoreData对象的数组。我在Player类中创建了以下函数，以计算出播放器的寿命：

public class Player: NSManagedObject {

func calculateDays() -> Int {

    let currentCalendar = Calendar.current
    guard let dob = currentCalendar.ordinality(of: .day, in: .era, for: self.dob as! Date) else {
        return 0
    }
    guard let today = currentCalendar.ordinality(of: .day, in: .era, for: Date()) else {
        return 0
    }
    let days = today - dob

    return days
}

}

dayNumber变量不显示的任何原因？我觉得我很想念这件事。任何想法都是魔术。