CODEWITHSUNDEEP
swiftcore-dataios-simulator
Jim
Jim

Reputation: 1470

Why does my app run in the simulator but crash trying to launch on my iPhone?

I'm writing an app in Swift 3 using Xcode 8.3.2. My app runs fine in the Simulator but I get an ugly error message when I try to run it on my iPhone (iOS 10.3.1):

   libswiftCore.dylib`function signature specialization <preserving fragile attribute, Arg[2] = Dead, Arg[3] = Dead> of Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, file : Swift.StaticString, line : Swift.UInt, flags : Swift.UInt32) -> Swift.Never:
    0x1005203d0 <+0>:   stp    x26, x25, [sp, #-0x50]!
    0x1005203d4 <+4>:   stp    x24, x23, [sp, #0x10]
    0x1005203d8 <+8>:   stp    x22, x21, [sp, #0x20]
    0x1005203dc <+12>:  stp    x20, x19, [sp, #0x30]
    0x1005203e0 <+16>:  stp    x29, x30, [sp, #0x40]
    0x1005203e4 <+20>:  add    x29, sp, #0x40            ; =0x40 
    0x1005203e8 <+24>:  mov    x19, x6
    0x1005203ec <+28>:  mov    x20, x5
    0x1005203f0 <+32>:  mov    x21, x4
    0x1005203f4 <+36>:  mov    x22, x3
    0x1005203f8 <+40>:  mov    x23, x2
    0x1005203fc <+44>:  mov    x24, x1
    0x100520400 <+48>:  mov    x25, x0
    0x100520404 <+52>:  adr    x8, #0xf11fc              ; protocol descriptor for Swift._DefaultCustomPlaygroundQuickLookable + 136
    0x100520408 <+56>:  nop    
    0x10052040c <+60>:  add    x0, x8, #0x10             ; =0x10 
    0x100520410 <+64>:  mov    w1, #0x28
    0x100520414 <+68>:  orr    w2, wzr, #0x7
    0x100520418 <+72>:  bl     0x100520750               ; swift_rt_swift_allocObject
    0x10052041c <+76>:  mov    x8, x0
    0x100520420 <+80>:  stp    x22, x21, [x8, #0x10]
    0x100520424 <+84>:  strb   w20, [x8, #0x20]
    0x100520428 <+88>:  str    w19, [x8, #0x24]
    0x10052042c <+92>:  adr    x3, #0x40440              ; partial apply forwarder for Swift.(_fatalErrorMessage (Swift.StaticString, Swift.StaticString, file : Swift.StaticString, line : Swift.UInt, flags : Swift.UInt32) -> Swift.Never).(closure #2)
    0x100520430 <+96>:  nop    
    0x100520434 <+100>: mov    x0, x25
    0x100520438 <+104>: mov    x1, x24
    0x10052043c <+108>: mov    x2, x23
    0x100520440 <+112>: mov    x4, x8
    0x100520444 <+116>: bl     0x1004014dc               ; function signature specialization <preserving fragile attribute, Arg[1] = [Closure Propagated : reabstraction thunk helper from @callee_owned (@unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> () to @callee_owned (@unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> (@out ()), Argument Types : [@callee_owned (@unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> ()]> of generic specialization <preserving fragile attribute, ()> of Swift.StaticString.withUTF8Buffer <A> ((Swift.UnsafeBufferPointer<Swift.UInt8>) -> A) -> A
->  0x100520448 <+120>: brk    #0x1

I set an exception breakpoint that led me to this bit of code:

    if let defaultFormula = dataManager.fetchDefaultFormula(moc) {
        self.formula = defaultFormula.first! <<< Unexpectedly found nil...
    }

and here is the function it's calling:

  func fetchDefaultFormula(_ moc: NSManagedObjectContext) -> [Formula]? {
        let defaultFormulaID = UserDefaults.formula()
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Formula")
        let filterPredicate = NSPredicate(format: "uuid = [c] %@", defaultFormulaID)
        fetchRequest.predicate = filterPredicate

        do {
            return try moc.fetch(fetchRequest) as? [Formula]
        } catch {
            fatalError("There was an error fetching the lifts")
        }
        return nil
    }

The fetch request is returning 0 values so it's clear why I get the exception when I force unwrap it. However, the object property 'formula' must have a value. The first thing the app does is check to see if the default data (like the available formulas) exists in the persistent store and if it doesn't, it adds it. I've reset the Simulator and it dutifully adds them but it seems that this isn't happening on the iPhone. If there's a way for me to determine whether or not the records are being added to the store when running it on the iPhone, please enlighten me.

I've found a few SO threads in which others have experienced this cryptic error (the big, ugly one, not the unexpected nil) and I've tried all of the remedies suggested:

I don't know where to go from here having exhausted all of the suggestions I've been able to find.

Any suggestions are greatly appreciated.

Upvotes: 1

Views: 329

Answers (1)

Jim
Jim

Reputation: 1470

Well, I guess there was one thing I didn't try - uninstalling the app from my phone first, then build and run it on the phone.

So I don't really know what the root cause was, but at least this resolved the problem.

Upvotes: 2

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