How to figure out what makes my iOS app crash (EXC_BREAKPOINT)? - ios

Question

How can I know where exactly did my app crash ?
I receive a lot of crash from my users but I can't reproduce the crash myself and the crash log does not indicate a specific line:
Thread : Crashed: com.apple.main-thread
0 myapp 0x22d1d4 specialized ItemType.init(coder : NSCoder) -> ItemType? (ItemType.swift)
1 myapp 0x22c72c #objc ItemType.init(coder : NSCoder) -> ItemType? (ItemType.swift)
2 EventKitUI 0x234734a5 (Missing)
3 EventKitUI 0x23479639 (Missing)
4 EventKitUI 0x234161db (Missing)
5 EventKitUI 0x234734a5 (Missing)
6 EventKitUI 0x234728d3 (Missing)
7 myapp 0x1e9df4 specialized Item.init(coder : NSCoder) -> Item? (Item.swift:162)
8 myapp 0x1db9b8 #objc Item.init(coder : NSCoder) -> Item? (Item.swift)
9 EventKitUI 0x234734a5 (Missing)
10 EventKitUI 0x234728d3 (Missing)
11 EventKitUI 0x23471bc7 (Missing)
12 myapp 0x26f370 savedSearchList.getLastItem() -> Item! (savedItemList.swift:71)
13 myapp 0x26c008 specialized MenuInitializerViewController.getSideMenuViewController() -> UIViewController (MenuInitializerViewController.swift:39)
14 myapp 0x18388c SharedAppDelegate.showMainInterface() -> () (SharedAppDelegate.swift:427)
15 myapp 0x18398c #objc SharedAppDelegate.showMainInterface() -> () (SharedAppDelegate.swift)
16 myapp 0x188a48 SharedAppDelegate.(retreiveFirstData(SharedAppDelegate) -> () -> ()).(closure #1) (SharedAppDelegate.swift:290)
17 myapp 0x2657a4 partial apply for UserAppData.(getFirstData(UserAppData) -> (() -> (), failure : (error : NSError) -> ()) -> ()).(closure #3) (UserAppData.swift:45)
18 myapp 0x263828 partial apply for thunk (UserAppData.swift)
19 myapp 0x268c28 UserAppData.(getDiffusionsGroup(UserAppData) -> (() -> (), failure : (error : NSError) -> ()) -> ()).(successBlock #1)(AFHTTPRequestOperation!, responseObject : AnyObject!)() (UserAppData.swift:788)
20 myapp 0x266684 partial apply for UserAppData.(getDiffusionsGroup(UserAppData) -> (() -> (), failure : (error : NSError) -> ()) -> ()).(successBlock #1)(AFHTTPRequestOperation!, responseObject : AnyObject!)() (UserAppData.swift)
21 libtzupdate.dylib 0x344ffe2f (Missing)
22 libtzupdate.dylib 0x344ffe1b (Missing)
23 libtzupdate.dylib 0x345046c9 (Missing)
24 CoreAudio 0x226dc535 (Missing)
25 CoreAudio 0x226daa2f (Missing)
26 CoreAudio 0x2262d0d9 (Missing)
27 CoreAudio 0x2262cecd (Missing)
28 GeoServices 0x2b9a2af9 (Missing)
29 UIKit 0x268b62dd UIApplicationMain + 144
30 myapp 0x10f2d4 main (AppDelegate.swift:16)
31 libtzupdate.dylib 0x34528873 (Missing)
I understand that it might come from ItemType unarchive initializer, but I don't see what could be wrong with it:
required convenience init?(coder aDecoder: NSCoder)
{
self.index = aDecoder.decodeIntegerForKey("index")
self.name = aDecoder.decodeObjectForKey("name") as! String
self.id = aDecoder.decodeObjectForKey("id") as! String
self.type = Type(rawValue: aDecoder.decodeIntegerForKey("type")) ?? .Default
}

Answer 1

Try adding a Exception breakpoint and/or Swift error breakpoint in
View->Navigator->Show Breakpoint Navigator
and then click the + icon on the bottom

Answer 2

I am not sure this is helping but these two lines are not very safe code
self.name = aDecoder.decodeObjectForKey("name") as! String
self.id = aDecoder.decodeObjectForKey("id") as! String
You are force casting the object as a String without checking if it has a value. ObjectsForKeys are nil by default until you set them the first time.
So these 2 lines can potentially cause a crash if you haven't set the object at least once. Try using the ?? nil coalescing operator to ensure this cannot happen.
self.name = aDecoder.decodeObjectForKey("name") as? String ?? self.name
self.id = aDecoder.decodeObjectForKey("id") as? String ?? self.id
Now you check if the object exits (as? String) and if it doesnt than it uses the default name/id (?? self.name)
I am not sure this is causing the crash but this should improve your code.
Your code to save the Enum seems alrite because you are using the ?? operator, so I dont think thats causing the issue.
You only need to do nil checks for ObjectsForKeys, because they are of type AnyObject and therefore dont know what object they actually are until set once, hence it could cause a nil crash.
Compare this to say BoolForKey where you dont have to do this because it knows you are dealing with boolean values and therefore it defaults to false automatically.
Also, you are doing the same thing I keep seeing here, which is not using constants for keys. This is just prone to typos.
Create a struct above your class
struct Key {
static let name = "Name"
static let id = "ID"
}
and than use the keys like so
...objectForKey(Key.name)
Hope this helps