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Core Data in Swift by Marcus S. Zarra

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Some Maintenance Before We Migrate

Before we actually release a new version of our application that migrates the data, we need to first complete a minor “maintenance” update for our users. Normally, we’d add this code to the very first version of our application, but just in case we wrote that first release before versioning was a consideration, we need to go back to our old version and add a small amount of code to help our users.

Some users will download the new version of an application to just “try it out” and see if it’s worth the upgrade price and the hassle. Normally this isn’t an issue—until we upgrade the data underneath our users. Then things go sideways. What we do not want to happen is the error message shown here.

Note that this ...

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