Contents

mesqueeb/swiftdatasugar

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Sample Project: SwiftDataTodoList

A point of reference on how to implement CRUD via SwiftData on all Apple platforms.

Features of this proof of concept:

  1. Writing uses a background thread (uses the @ModelActor macro)
  2. Reading uses MainActor thread (uses SwiftUI's @Query macro)
  3. Migration setup with unit testing
  4. Full Multi-platform support

1. Writing data

  • Writing data to the SwiftData models is done on a background thread
  • An actor that conforms to ModelActor has been set up with CRUD-like methods to easily write data to the model
  • This actor is called DbCollection
  • Instantiating DbCollection must be done on @MainActor to prevent an issue where writing data isn't reactive in SwiftUI. (see detailed explanation at A New Issue: The View Does Not Refresh After Data Update, an issue I've reported to Fatbobman and prompted him to write an article on)
  • DbCollection can be used for multiple models
  • in this app the usage of DbCollection is showcased for a Todo model
// example instantiating multiple collections in the `@main` swift file
@MainActor public let dbTodos = DbCollection<TodoItem>(modelContainer: modelContainer)
@MainActor public let dbUsers = DbCollection<User>(modelContainer: modelContainer)

2. Reading data

  • Reading data from the SwiftData models is done on the MainActor thread
  • SwiftUI's @Query can be used for simple views that need to query data without dynamic requirements
  • The usage of @Query is wrapped in new view called DbQuery where you can pass a dynamic predicate and sortBy instances that queries data
  • in this app the usage of DbQuery is showcased for a list that can be filtered and sorted dynamically
DbQuery(predicate: activePredicate, sortBy: activeSort) { items in
  ForEach(items, id: \.id) { item in
    TodoListItemView(item: item)
      .id(item.id) // Use ID for List reordering and animations
    }
  }
}

3. Migration setup with unit testing

  • Custom Migrations in SwiftData, which are hard to get right, are showcased in this app with 3 versions and 2 migrations
  • The latest schema has all of its structs and models type aliased for easier use throughout the codebase
  • Only data crucial to migrations is scoped inside of the versioned schema, other usefull methods and convenience initialisers are extended only on the latest schema
  • Actual migration logic neatly organised per-version: it bundles just the logic to upgrade to the relevant version in the same file as that version's schema
  • The final combined migration plan combines each migration step per version
  • Full unit testing in place of each migration phase (with modern Swift Testing) to give confidence a latest migration will not crash your user's apps on launch
  • The unit testing showcases exaclty how to test migrations in SwiftData

4. Multi-Platform Support

  • All code used in this proof of concept is compatible with all Apple platforms

Package Metadata

Repository: mesqueeb/swiftdatasugar

Default branch: main

README: README.md