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I get this error in the debugger everytime core data is used (so if I make 3 calls I get the warning 3 times).

CoreData: annotation: Failed to load optimized model at path '/var/containers/Bundle/Application/0B6C2326-D8D5-47B3-8C68-7693C16A0806/liveDemo.app/liveDemo.momd/liveDemo.omo'

It does not cause any instant problem, but whilst they add up, it gradually slows down the app until it crashes with a NSException (it's irrelevant what the user does at the time, it will just lag more and more then come to a crash at whatever point in the app).

I have tested the app on 3 devices (iPhone 7+ - iOS 11, iPhone 7 - iOS 11, iPad Aid - iOS 10.3) and it ONLY occurs on the iPad. However when I started the project one of the phones had a version of iOS 10 installed and it did not cause any issues so although I can't fully exclude it, it seems unlikely it's the OS version to blame.

Steps tried

  1. Uninstall and install app, so the device clears core data file, also tried restarting with and without the app installed - FAILED

  2. Remove and rewrite the Scheme in Xcode - FAILED

  3. Recreate the NSManagedObjectSubclass of the datamodel - FAILED

Has anyone encountered anything similar with recent versions of Xcode and managed to fix it? This is a 2 year old similar problem, but none of the answers have helped.

Alex Ioja-Yang
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  • I have the same issue here https://stackoverflow.com/questions/46876580/ios-9-10-coredata-failed-to-load-optimized-model-at-path – DJ-Glock Oct 23 '17 at 19:21

1 Answers1

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So, after a few days I have managed to solve it. I'm not familiar enough with the insides of Xcode, but all I had to do was rewrite the CoreData Model. Best to make a back up before trying this!

  1. Take a screenshot of current attributes and delete the CoreDataModel ( .xcdatamodeld file)
  2. Add a new file to project (Data Model template)
  3. Write old attributes
  4. Recompile and build

My assumption would be that the problem was caused after migrating a project started in Xcode 8 (written in Swift 3) to Xcode 9 (upgraded to Swift 4). It had no problem with devices running iOS 11 (same upgrade level as Xcode 9), but found it to consistently cause lag and eventually crashes in older iOS versions.

I don't understand why simply modifying file properties did not fix it, but I'm happy to have fixed it and move on.

Alex Ioja-Yang
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  • Worked with my app in test phase. But what if it is already in App Store, and it has more model versions due to lightweight migration? You can't just delete one version from Xcode, only the whole .xcdatamodeld file. When you delete and replace it, you risk that user's app will crash, specially if you only re-add the last version. Or should we re-add the old versions too, and make the current selected? – Gergely Kovacs Dec 13 '19 at 22:34