Swift crash reports don't make sense to me - ios

Question

This is the crash log I got from Crashlytics:
Thread : Crashed: com.apple.main-thread
0 Trenìt! 0x1000b93e4 SearchHistoryProvider.getMostRecentStations(Int) -> [String] (SearchHistoryProvider.swift)
1 Trenìt! 0x10007985c specialized MasterViewController.onTouchedTextField(UITextField) -> () (MasterViewController.swift:265)
2 Trenìt! 0x100075414 #objc MasterViewController.onTouchedTextField(UITextField) -> () (MasterViewController.swift)
3 UIKit 0x186fa0ad0 -[UIApplication sendAction:to:from:forEvent:] + 100
4 UIKit 0x186fa0a4c -[UIControl sendAction:to:forEvent:] + 80
5 UIKit 0x186f88740 -[UIControl _sendActionsForEvents:withEvent:] + 436
6 UIKit 0x186fa9248 -[UIControl touchesBegan:withEvent:] + 400
7 UIKit 0x186f9fdc0 -[UIWindow _sendTouchesForEvent:] + 376
8 UIKit 0x186f98b08 -[UIWindow sendEvent:] + 784
9 UIKit 0x186f68f4c -[UIApplication sendEvent:] + 248
10 UIKit 0x186f67528 _UIApplicationHandleEventQueue + 6568
11 CoreFoundation 0x181dd5124 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
12 CoreFoundation 0x181dd4bb8 __CFRunLoopDoSources0 + 540
13 CoreFoundation 0x181dd28b8 __CFRunLoopRun + 724
14 CoreFoundation 0x181cfcd10 CFRunLoopRunSpecific + 384
15 GraphicsServices 0x1835e4088 GSEventRunModal + 180
16 UIKit 0x186fd1f70 UIApplicationMain + 204
17 Trenìt! 0x10009b2fc main (AppDelegate.swift:14)```
(edited)
and this is my code:
MasterViewController.swift:
263 func showRecentStations(textField: UITextField) {
264 textField.text = ""
265 suggestionStations = masterContainerManager!.homeController?.searchHistoryProvider?.getMostRecentStations(10)
266 updateStationsTable(textField)
267 }
SearchHistoryProvider.swift
func getMostRecentStations (maxSize : Int) -> [String] {
let stationsByOldestArray = getRecentStationsByOldest()
let stations = NSMutableOrderedSet()
for i in (0...(stationsByOldestArray.count-1)).reverse() {
stations.addObject(stationsByOldestArray[i].depStation)
if stations.count==maxSize {
return stations.array as! [String]
}
stations.addObject(stationsByOldestArray[i].arrStation)
if stations.count==maxSize {
return stations.array as! [String]
}
}
return stations.array as! [String]
}
Can anyone understand what's the crash about?

Answer 1

I found the bug:
in case stationsByOldestArray.count was 0
the for loop would have been
for i in (0...-1).reverse()
I fixed it by rewriting the loop as
for i in (0..<stationsByOldestArray.count).reverse()
However I think the Swift crash reports are often hopelessly unhelpful!