I am new to core data, can anyone let me know the difference between Versioning and Data migration. When we do versioning and when we Data Migration?
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I am new to core data, can anyone let me know the difference between Versioning and Data migration. When we do versioning and when we Data Migration?
Versioning is used just like versioning on apps to indicate different evolving variations of the same basic code except in Core Data the code evolving is the data model i.e. the entities, entity properties and relationships defined in the .xcdatamodel file.
Migration is what you perform on the end user’s existing data in the persistent store in order to format/structure the store to work with the new version of the data model.
It works like this:
You release version 1.0 of your app which as a data model with a version of 1.0 as well. End user then use your app and save their data in a persistent store formatted/structure using your data model 1.0.
Then you release version 2.0 of your app and you make changes to the data model in the process e.g. you change a property name, add a property or add an entity. You would version the data model as well to something like 2.0 (the actual version names are arbitrary.) You then provide for either automatic or manual migration such that the end user data in the 1.0 persistent store file can be reformatted to the data model 2.0 format.