在 EKCalendar 中检查 nil

Question

我正在开发一个从特定 iOS 日历获取事件的应用程序。但是，当该日历为空时，我当然会收到致命的 nil 错误。

let calendar = calendarWithTitle("Personal Trainer's Tool",
            type: EKCalendarTypeCalDAV,
            source: icloudSource!,
            eventType: EKEntityTypeEvent)

/* Create the predicate that we can later pass to the event store in order to fetch the events */
        let searchPredicate = eventStore.predicateForEventsWithStartDate(
            startDate,
            endDate: endDate,
            calendars: [calendar!])

/* Fetch all the events that fall between the starting and the ending dates */
        events = eventStore.eventsMatchingPredicate(searchPredicate) as [EKEvent] //Error on this line


if events.count == 0 {
                println("No events could be found")
            } else {

                // Go through all the events and print them to the console
                for event in events{
                    println("Event title = \(event.title)")
                    println("Event start date = \(event.startDate)")
                    println("Event end date = \(event.endDate)")
                }
            }

我的 searchPredicate 中的 'calendar' 应该是一个 EKCalendar，但我不知道如何在允许 searchPredicate 执行之前检查它是否为空以避免致命错误。有人知道如何解决这个问题吗？

谢谢

Answer 1

您可以使用可选绑定：

let calendar = calendarWithTitle("Personal Trainer's Tool",
    type: EKCalendarTypeCalDAV,
    source: icloudSource!,
    eventType: EKEntityTypeEvent)

/* Create the predicate that we can later pass to the event store in order to fetch the events */
let searchPredicate = eventStore.predicateForEventsWithStartDate(
    startDate,
    endDate: endDate,
    calendars: [calendar!])

/* Fetch all the events that fall between the starting and the ending dates */
if let events = eventStore.eventsMatchingPredicate(searchPredicate) as? [EKEvent] {


    if events.count == 0 {
        println("No events could be found")
    } else {

        // Go through all the events and print them to the console
        for event in events{
            println("Event title = \(event.title)")
            println("Event start date = \(event.startDate)")
            println("Event end date = \(event.endDate)")
        }
    }
}

在 EKCalendar 中检查 nil

Checking for nil in an EKCalendar

ios

eventkit

ekeventstore

swift

ios8