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xcodecore-datacore-data-migrationxcdatamodel

Do multiple versions of xcdatamodel mean that we need multiple xcmappingmodel files?

I have multiple versions of xcdatamodel files:

app1.0.xcdatamodel
app1.1.xcdatamodel
app1.2.xcdatamodel (current)

Does this mean I need multiple combinations of xcmappingmodel files to cover all upgrade scenarios?

app1.0_to_app1.1.xcmappingmodel (had this already)
app1.1_to_app1.2.xcmappingmodel (is it iterative?)
app1.0_to_app1.2.xcmappingmodel (too much?)

Thanks!

Solution

  • Core Data requires that you create a mapping model to go from the current version of the data store to the latest version of the data store. This means that you will need to make one that goes from v1 -> v2 and v2 -> v3 and v1 -> v3.

    From Core Data Versioning and Migration Guide

    Tries to find a mapping model that maps from the managed object model for the existing store to that in use by the persistent store coordinator. Core Data searches through your application’s resources for available mapping models and tests each in turn. If it cannot find a suitable mapping, Core Data returns NO and a suitable error.

    Note that you must have created a suitable mapping model in order for this phase to succeed.

    As discussed in this Apple Document Core Data Mapping