A short walkthrough of migrating persisted app data in a Swift app after changing a Codable struct: I copy the old struct under a versioned name, and init() attempts to decode saved JSON with the new model first, falling back to the old one and converting items across. I note the migration code is deliberately messy and temporary, since the app only exists on my phone and a couple of simulators...
Progress on my SwiftUI habit tracking app built for the 100 Days challenge, covering UI refinements like a fading checkmark and the shift from simulator testing to daily use on a real iPhone. Persistence uses Swift’s built-in JSON encoding with UserDefaults, which works well until the struct changes — I discuss the resulting decode failures and the lack of a simple way to decode missing properties using default values...
