Extended sample program to demonstrate how CoreData can be used with SwiftUI. This sample has been sort of a play ground to try to duplicate or reinvent some familiar UIKit patterns using SwiftUI that are common with some Core Data based Apps.
This project currently compiles and runs on Xcode Version 11.2.1 (11B500) Current development testing has mostly been on iPhone devices. It does run on iPad and macOS with a few size class issues (not a priority for me here.)
The key component of this sample is the class CoreDataDataSource which encapsulates much of the functionality of an NSFetchedResultsController for use with SwiftUI. This version of CoreDataDataSource has several custom initializers for extended capabilities.
This project is still a work in progress. Several more changes will be made in the near future.
The App uses a Tab View that displays and edits the same CoreData database several ways.
Tab 1: Typical "drill-down" view with Lists and Detail view editing
Tab 2: Two side-by-side instances of the same view as in Tab 1. This is helpful to see that the Core-data changes are observed by all views properly.
Tab 3: Has a Data Source set up to support a nested SwiftUI Grouped List with correct implementations of move and delete within a group.
Tab 4: Demonstrates Selecting rows within a List It uses a generic ListSelectionManager to allow specific actions (e.g. updating database) at the time on the selection or deselection, in addition to inserting and deleting from the selection Set. It also demonstrates how to create a custom ToggleStyle to use instead of the Default Switch ToggleStyle. Selecting Items is only allowed in Edit mode, which also exposes several commands when active.
Tab 5: Demonstrates how to use a SearchBar with the CoreDataDataSource Added a new method to load the data source using an NSPredicate to supply data to a ForEach List. Created a UIViewRepresentable SearchBar that accepts the search text and returns a new NSPredicate back to the SwiftUI view after each keystroke.
- Thanks to @kontiki for insight on how to correctly use the editMode environment var. https://stackoverflow.com/questions/57496453/swiftui-how-do-i-make-edit-rows-in-a-list
https://github.com/Whiffer/SwiftUI-Core-Data-Test/issues/1 There is a weird issue when reordering rows in a list. This only happens when dragging a row up, and only when dragged one position up.
There were occasional crashes due to having used NavigationLink's as navigationBarItems. This used to work fine, but now seems to crash. This problem was fixed by adding the HiddenNavigationLink() and ActivateButton() helper views.