Core data updating model
Otherwise the mapping model will not be applied when updating from that release.
That is where custom mapping models come into play. EXAMPLE SCENARIO Let us assume we have a view controller that shows comments. Furthermore, the server delivering the data sends the creation date in a custom format that requires further processing.
We released our app to the App Store, just to realize afterwards that it would have been more efficient to store the transformed timestamp in our entity instead of doing the transformation whenever we access this attribute.
Resetting the simulator or reinstalling your app will do the trick.
But if your app was already released on the App Store you want to guarantee your customers a smooth update process.
Thus, let us add a new model version, update the type of the timestamp attribute from and set this model version to be the current version.Since Core Data will not be able to infer the mapping model on its own, let us create a custom mapping model. CUSTOM MAPPING MODELS To create a custom Core Data mapping model: IMPORTANT NOTE: If your Core Data model evolved over several versions since your last App Store release, you have to choose the version used in your App Store release as the source in the mapping model!