Mapping Model created for models that contain a derived attribute don't match entity version hashes
Originator: | me | ||
Number: | rdar://FB9044112 | Date Originated: | 2020-03-15 |
Status: | Open | Resolved: | |
Product: | Xcode | Product Version: | Version 12.4 (12D4e) |
Classification: | Reproducible: | Always |
Xcode create invalid mapping models for Core Data models that have a date derived attribute which derivation expression is `now()`. For those entities `sourceEntityVersionHash` and `destinationEntityVersionHash` for the mapping doesn’t match the version hash in the source and destination models. For automatic migrations the mapping model isn’t used because the hashes don’t match. So I created a sample project with a manual migration which the mapping model is loaded from a specific file or inferred. When migrating from the mapping model `Persistence.migrationModel = .migrationModel` the migration fails with error: "Mismatch between mapping and source/destination models" When migrating with inferred model `Persistence.migrationModel = .infered` the migration don’t fail but it isn’t possible to customize it. As a workaround I create the option `Persistence.migrationModel = .fixedMigrationModel`, which will check if the version hashes don’t match and force them to be equal if the entity have a derived attribute of `Date` type and with derivation expression is `now()`. The sample project can be found at https://github.com/diogot/CoreDataModelMigrationBug
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The problem also occurs with derived attributes whose derivation expressions are different from now() (i.e. @count)