Question

我使用dispatch_group编写了一个方法：

class func loadNewEvents(inContext context:NSManagedObjectContext, completion:(() -> Void)?=nil) {
    DDLogDebug("Loading New Events")
    let context = CoreDataManager.backgroundContext()
    let events = CoreDataManager.fetch(Event.self, inContext: context)
    var earliestEvent = events.sort({$0.initialTimestamp.integerValue > $1.initialTimestamp.integerValue}).first

    let group = dispatch_group_create()
    var loadedEvents:[Event]?
    var failure = false
    while (loadedEvents == nil || loadedEvents!.count != 0) && !failure {
        dispatch_group_enter(group);
        if let earliestTimeStamp = earliestEvent?.initialTimestamp.longLongValue {
            let url = afterUrl(earliestTimeStamp)
            getEvents(url: url,
                success: { events in
                    loadedEvents = events
                    earliestEvent = events.last
                    dispatch_group_leave(group)
                },
                failure: {
                    failure = true
                    dispatch_group_leave(group)
                }
            )
        } else {
            break
        }
        dispatch_group_wait(group, DISPATCH_TIME_FOREVER)
    }
    DDLogDebug("Loaded new events")
}

它在iOS9模拟器和带有iOS9的iPhone5S上运行良好。但是在带有iOS8的iPhone 4S上，方法的最后会发生崩溃：

EXC_BREAKPOINT (code=EXC_ARM_BREAKPOINT, subcode=0xdefe)

中的

_dispatch_semaphore_dispose

知道会导致这种情况的原因以及如何解决这个问题？

Answer 1

我终于找到了问题：我没有让小组离开break。

要解决此问题，我在dispatch_group_enter(group)内拨打了if let，因为当我没有进行异步通话时不需要它。

iPhone 4s / iOS 8上的Dispatch_Group崩溃

1 个答案: