Adopting SwiftData for a Core Data app

At a glance

Project structure

Source bundle/
├── Trips-Coexistence/
│   ├── Trips/
│   │   ├── TripsApp.swift
│   │   └── BucketListView.swift
│   └── TripsWidget/
│       └── TripsWidgetBundle.swift
├── Trips-CoreData/
│   └── Trips/
│       ├── TripsApp.swift
│       └── BucketListView.swift
└── Trips-SwiftData/
    ├── Trips/
    │   ├── TripsApp.swift
    │   ├── ContentView.swift
    │   ├── LocationSearchView.swift
    │   └── BucketListView.swift
    ├── TripsWidget/
    │   └── TripsWidgetBundle.swift
    └── Shared/
        ├── DataModel.swift
        └── Trip.swift

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 17 project/configuration file(s) and 77 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["Trips-Coexistence"]
    V2["Trips-CoreData"]
    V3["Trips-SwiftData"]
    Boundary["CoreData APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary
    Bundle --> V3
    V3 --> Boundary

Reference code

Trips-Coexistence/Trips/TripsApp.swift:10 — architecture anchor

@main
struct TripsApp: App {
    let persistenceController = PersistenceController.shared

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(\.managedObjectContext,
                              persistenceController.container.viewContext)
        }
    }
}

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    BucketListView o-- CDTrip : trip
    BucketListView o-- FetchedResults : bucketList
    BucketListView o-- Bucketlist : _bucketList
    BucketListItemToggle o-- CDBucketListItem : item

Ownership evidence

Trips-Coexistence/Trips/BucketListView.swift:12 — stored dependency or nearest verified ownership anchor

struct BucketListView: View {
    var trip: CDTrip
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

Trips-Coexistence/TripsWidget/PreviewSampleData.swift:14 — representative execution boundary

actor PreviewSampleData {
    // ...
        let schema = Schema([Trip.self, BucketListItem.self, LivingAccommodation.self])
    // ...
}

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

Trips-Coexistence/Trips/TripsApp.swift:11 — representative type boundary

@main
struct TripsApp: App {
    let persistenceController = PersistenceController.shared
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

Trips-Coexistence/Trips/AddBucketListItemView.swift:13 — representative boundary

struct AddBucketListItemView: View {
    // ...
    @Environment(\.dismiss) private var dismiss
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: App: TripsApp; Controller: MapCameraController, PersistenceController; Model: DataModel; Provider: Provider; View: AddBucketListItemView, AddTripView, BucketListItemView, BucketListView, ContentView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: completerDidUpdateResults, completer, selectCompletion, deleteItems, saveContext.
• Files: Trips-Coexistence/Trips/TripsApp.swift, Trips-CoreData/Trips/TripsApp.swift, Trips-SwiftData/Trips/TripsApp.swift, Trips-Coexistence/TripsWidget/TripsWidgetBundle.swift, Trips-SwiftData/TripsWidget/TripsWidgetBundle.swift, Trips-SwiftData/Trips/ContentView.swift.

Architecture takeaways

• TripsApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, SwiftData, WidgetKit, CoreData through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation