我有这个功能从我的Parse服务器检索视频：
func downloadVideo(marker: GMSMarker)
{
print("printing")
print(markerLat)
print(markerLong)
print("A")
let query = PFQuery(className:"UploadedVideoCurrent")
print("b")
//query.whereKey("GPS", equalTo: PFGeoPoint(latitude: markerLat, longitude: markerLong))
query.findObjectsInBackgroundWithBlock { (objects, error) in
print("c")
if(error == nil)
{
print("d")
for object in objects!
{
print("made it")
self.file = (object.objectForKey("VideoFile") as! PFFile)
//self.thumbnail = (object.objectForKey("Thumbnail") as! PFFile)
self.userofVideo = object.objectForKey("User")
self.hour = object.objectForKey("Hour")
self.minutes = object.objectForKey("minutes")
self.street = object.objectForKey("Location")
print(self.file!.url)
self.downloadedurl = self.file!.url
var tempLat = object.objectForKey("GPS")!.latitude as Double
var tempLong = object.objectForKey("GPS")!.longitude as Double
//print(tempLong)
//print(tempLat)
print(tempLat.roundToPlaces(3))
print(self.markerLat.roundToPlaces(3))
print(tempLong.roundToPlaces(3))
print(self.markerLong.roundToPlaces(3))
if(tempLat.roundToPlaces(3) == self.markerLat.roundToPlaces(3) && tempLong.roundToPlaces(3) == self.markerLong.roundToPlaces(3)){
print("success")
self.postsLat = tempLat
self.postsLong = tempLong
}
//print(self.postsLong)
//print(self.postsLat)
//var coordinates = [postsLat, postsLong, x]
}
}
else
{
print("didn't make it")
print(error)
}
}
}
然而，它仅适用于我调用它的某些情况，而我似乎无法理解为什么。在viewdidload和一个IBAction中，我点击downloadvideo运行良好：
@IBAction func snapNext(sender: AnyObject) {
if self.z != 1{
x = x! + 1
var count = markers.count
print("This is the markers count: \(markers.count)")
print(x)
if x < markers.count {
self.viewMap.camera = GMSCameraPosition.cameraWithTarget(self.markers[x!], zoom: 16.9)
} else {
self.viewMap.camera = self.camera!
x = 0
}
//viewMap.camera = marker.userData[0]
}else{
self.viewMap.camera = self.camera!
}
var count = 0
if markers.count > 3 {
while count < 3 {
self.marker = GMSMarker(position: markers[x!])
print(self.marker)
print(markers[x!])
downloadVideo(marker)
count = count + 1
}
}else if markers.count == 3 {
self.marker = GMSMarker(position: markers[2])
print(self.marker)
print(markers[2])
downloadVideo(marker)
self.marker = GMSMarker(position: markers[1])
print(self.marker)
print(markers[1])
downloadVideo(marker)
self.marker = GMSMarker(position: markers[0])
print(self.marker)
print(markers[0])
downloadVideo(marker)
}else if markers.count == 2{
self.marker = GMSMarker(position: markers[1])
print(self.marker)
print(markers[1])
downloadVideo(marker)
self.marker = GMSMarker(position: markers[0])
print(self.marker)
print(markers[0])
downloadVideo(marker)
}else if markers.count == 1 {
self.marker = GMSMarker(position: markers[0])
print(self.marker)
print(markers[0])
downloadVideo(marker)
}else {
}
}
然而，当我通过点击GMSmarker来调用它时，只是在打印B作为控制台的下一个输出的行之后崩溃或跳过查询是致命错误：在运行以下代码后意外地发现nil：
func mapView(mapView: GMSMapView, didTapMarker marker: GMSMarker) -> Bool {
if z == 0 {
let lat = marker.position.latitude as Double
let long = marker.position.longitude as Double
markerLat = lat.roundToPlaces(6)
markerLong = long.roundToPlaces(6)
//self.marker = GMSMarker(position: markers[2])
x = 1
downloadVideo(marker)
if(self.postsLat!.roundToPlaces(3) == self.markerLat.roundToPlaces(3) && self.postsLong!.roundToPlaces(3) == self.markerLong.roundToPlaces(3))
{
self.performSegueWithIdentifier("playerSegue", sender: nil)
print("a")
file!.getDataInBackgroundWithBlock({ (data, error) in
if error == nil
{
self.mp4 = data
print(data)
print(self.mp4)
print("a")
}
})
}else{
print("not playing")
print(self.postsLat!.roundToPlaces(3))
print(self.markerLat.roundToPlaces(3))
print(self.postsLong!.roundToPlaces(3))
print(self.markerLong.roundToPlaces(3))
}
}else{
}
return true
}
考虑到查询不使用甚至被调用的变量而且c永远不会被打印出来，我甚至不知道这是怎么回事。