21、Core Data Relationships and GUI Enhancement

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于 2025-11-12 16:01:54 发布

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分类专栏：解密Cocoa编程精髓文章标签： Core Data Data Migration GUI Enhancement

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Core Data Relationships and GUI Enhancement

1. Data Migration

When dealing with data migration, it will attempt a lightweight migration by inferring the mapping. If the mapping can’t be inferred, the process stops, and the method returns nil with an error. In such a case, the code [[NSApplication sharedApplication] presentError:error] will make the application show an error saying “The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store.”

However, in this situation, there are two models available, and the mapping can be inferred. So, the lightweight migration is done automatically, with the old data file backed up first in case of issues.