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I have the following model:

Model Version 1

parent is a to-one relationship (optional, no minimum, maximum=1). children is the inverse to-many relationship (optional, no minimum, no maximum).

I added a new model version, where only the Entity Room is renamed to Classroom, all other entities are unchanged:

Model Version 2

I also created a mapping model for the migration, but the migration fails with the error message

reason = "Can't find mapping model for migration";

The strange thing is that if the parent relationship is created with minimum=1 (instead of no minimum) then the migration works without problems.

The persistent store is opened with the options

NSDictionary *options = @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@NO};
Christoph R
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1 Answers1

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Why do you need a mapping model? You should avoid these complexities and simply use Lightweight Migration as explained in Apple's Lightweight Migration Documentation.

Mundi
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  • The model is a reduced example of my actual model, which is more complicated and has more changes which don't work with lightweight migration. I just tried to reduce the problem as far as possible – Christoph R Mar 29 '13 at 12:42
  • Then your info about the model change is misleading. Please post the change that you need custom migration for. – Mundi Mar 29 '13 at 12:57