Question

I am working on an App update and this version is completely built from scratch and has completely new coreData model schema. I need to write coreData migration from the older model. I have been looking at resources to write coreData migration but all of them need old model file. Since this version is completely new, I don’t have the old model schema.

Is there any way I can write the migration such that it dumps the old model when user updates the app?

Thanks in advance

Answer 1

If you have the old App, then you can recreate the model from the compiled model file which is contained in the App bundle:

• Sync the App to iTunes, if necessary.
• Ctrl-Click on the App in iTunes, and use “Show in Finder” to locate the “YourApp.ipa” file.
• Copy “YourApp.ipa” to a temporary directory, and use “unzip YourApp.ipa” on the command line to extract the archive.
• In the extracted “Payload/YourApp.app” folder there should be a “XXX.momd” folder containing a file “XXX.mom” (XXX is the name of the model). This is the compiled model file.
• In your Xcode project (or a temporary project), create a new “Data Model” file “XXX.xcdatamodeld”.
• Select this file and choose “Editor -> Import …” from the menu.
• In the import dialog, choose the “XXX.mom” file from above.