How to create a app specific Calendar in Swift 3

I tried to create a calendar from my app. It does not work on an iPhone 6, the app crashed.

Here is my code:

do {
    let calender = EKCalendar(for: .event, eventStore: eventStore)
    calender.title = "MyApp"
    calender.source = eventStore.defaultCalendarForNewEvents.source
    try eventStore.saveCalendar(calender, commit: true)
    userDefaults.set(calender.calendarIdentifier, forKey: calendarIdentifierKey)
    userDefaults.synchronize()
} catch  {
    print("Error occurred while creating calendar ")
}

Update

1. In the phone the default calendar is set as xxx.gmail.com

2. And the following error is thrown

   Error occurred while creating calendar 
   

I finally found the answer.

do {
        let calender = EKCalendar(for: .event, eventStore: eventStore)
        calender.title = "MyApp"
        let sourcesInEventStore = eventStore.sources
        let filteredEventStores = sourcesInEventStore.filter{
            (source: EKSource) -> Bool in
            source.sourceType.rawValue == EKSourceType.local.rawValue || source.title.equalsIgnoreCase("iCloud")
        }
        if filteredEventStores.count > 0 {
            calender.source = filteredEventStores.first!
        } else {
            calender.source = sourcesInEventStore.filter{
                (source: EKSource) -> Bool in
                source.sourceType.rawValue == EKSourceType.subscribed.rawValue
                }.first!
        }
        try eventStore.saveCalendar(calender, commit: true)
        userDefaults.set(calender.calendarIdentifier, forKey: calendarIdentifierKey)
        userDefaults.synchronize()
    } catch  {
        print("Error occurred while creating calendar ")
    }