PacBag
LiveAn iOS app that tracks what’s in each bag and weighs it against the airline limit before you leave the house.
Free, no account, no server. You own all your data.
Building the data model in code
CoreDataManager constructs the entire Core Data model at runtime in 428 lines of Swift rather than loading a .xcdatamodeld file: 5 entities, 38 attributes, 12 relationships, handed to an NSPersistentCloudKitContainer.
CloudKit refuses a model that doesn’t meet its constraints, and it refuses at launch rather than at compile time. Every attribute must be optional or carry a default, and every relationship must declare an inverse. Doing that by hand means 38 of 38 attributes set optionality explicitly, 29 carry defaults, and all 12 relationships name their inverse. Getting one wrong is a crash on first run, on a stranger’s phone.
What it doesn’t have
Almost no tests. The unit-test target is still the Xcode template. The UI-test target has two tests of the weight arithmetic, plus the screenshot test that produces the App Store images.