Progressive Data Migration (An Academic Exercise)
We’re going to wrap up this chapter with a final section that’s primarily a mental and academic exercise, one that demonstrates the flexibility available when working with Core Data migrations. Since it’s possible to insert custom code at nearly every point in a migration, we can do some very interesting things. Let’s take a look at an example.
What happens when our application is at version 5 of its data model and a user at version 1 decides to upgrade? Normally, we’d need to provide a mapping model for every combination of source and destination object models. For the first couple of versions, this isn’t an issue. However, as we get further away from version 1, it becomes increasingly difficult. ...
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