Core Data'dan SwiftData'ya Geçiş: Adım Adım Kılavuz 2026

// Migration assessment checklist

/*
 FEATURES SUPPORTED BY SWIFTDATA:
 ✅ Simple models with basic properties
 ✅ One-to-one and one-to-many relationships
 ✅ Optional properties and default values
 ✅ Transformable attributes (via Codable)
 ✅ CloudKit synchronization (basic)
 ✅ Automatic lightweight migrations
 ✅ Class inheritance (iOS 26+)

 FEATURES REQUIRING ATTENTION:
 ⚠️ NSFetchedResultsController → @Query + manual observation
 ⚠️ NSCompoundPredicate → #Predicate with combined logic
 ⚠️ Dynamic predicates → Workarounds required

 UNSUPPORTED FEATURES:
 ❌ Advanced CloudKit Sharing
 ❌ Derived attributes
 ❌ Fetched properties
*/

// Example of typical Core Data model to migrate
import CoreData

// Existing Core Data entity
class CDTask: NSManagedObject {
    @NSManaged var id: UUID
    @NSManaged var title: String
    @NSManaged var isCompleted: Bool
    @NSManaged var createdAt: Date
    @NSManaged var priority: Int16
    @NSManaged var category: CDCategory?
}

class CDCategory: NSManagedObject {
    @NSManaged var id: UUID
    @NSManaged var name: String
    @NSManaged var color: String
    @NSManaged var tasks: NSSet?
}

import SwiftData

// SwiftData equivalent of CDTask
@Model
final class Task {
    // Properties with default values
    var id: UUID = UUID()
    var title: String = ""
    var isCompleted: Bool = false
    var createdAt: Date = Date()
    var priority: Int = 0

    // Optional relationship to Category
    var category: Category?

    // Explicit initializer recommended
    init(
        id: UUID = UUID(),
        title: String,
        isCompleted: Bool = false,
        createdAt: Date = Date(),
        priority: Int = 0,
        category: Category? = nil
    ) {
        self.id = id
        self.title = title
        self.isCompleted = isCompleted
        self.createdAt = createdAt
        self.priority = priority
        self.category = category
    }
}

import SwiftData

@Model
final class Category {
    var id: UUID = UUID()
    var name: String = ""
    var color: String = "blue"

    // Inverse relationship with delete rule
    @Relationship(deleteRule: .cascade, inverse: \Task.category)
    var tasks: [Task] = []

    init(id: UUID = UUID(), name: String, color: String = "blue") {
        self.id = id
        self.name = name
        self.color = color
    }
}

import SwiftData
import SwiftUI

@main
struct TaskManagerApp: App {
    // SwiftData container configuration
    var sharedModelContainer: ModelContainer = {
        // Schema including all models
        let schema = Schema([
            Task.self,
            Category.self
        ])

        // Configuration with storage options
        let modelConfiguration = ModelConfiguration(
            schema: schema,
            isStoredInMemoryOnly: false,
            // Use the same store as Core Data
            url: URL.applicationSupportDirectory
                .appending(path: "TaskManager.sqlite")
        )

        do {
            return try ModelContainer(
                for: schema,
                configurations: [modelConfiguration]
            )
        } catch {
            fatalError("Could not create ModelContainer: \(error)")
        }
    }()

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .modelContainer(sharedModelContainer)
    }
}

import CoreData
import SwiftData

// Configuration for coexistence
class PersistenceController {
    static let shared = PersistenceController()

    // Shared store between Core Data and SwiftData
    private let storeURL: URL = {
        let appSupport = FileManager.default
            .urls(for: .applicationSupportDirectory, in: .userDomainMask)
            .first!
        return appSupport.appending(path: "TaskManager.sqlite")
    }()

    // MARK: - Core Data Stack (existing)

    lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "TaskManager")

        // Configure to use shared store
        let description = NSPersistentStoreDescription(url: storeURL)
        description.setOption(
            true as NSNumber,
            forKey: NSPersistentHistoryTrackingKey
        )
        container.persistentStoreDescriptions = [description]

        container.loadPersistentStores { _, error in
            if let error = error as NSError? {
                fatalError("Core Data error: \(error)")
            }
        }

        return container
    }()

    // MARK: - SwiftData Stack (new)

    lazy var swiftDataContainer: ModelContainer = {
        let schema = Schema([Task.self, Category.self])

        let config = ModelConfiguration(
            schema: schema,
            url: storeURL,
            // Disable automatic migrations in coexistence
            allowsSave: true
        )

        do {
            return try ModelContainer(for: schema, configurations: [config])
        } catch {
            fatalError("SwiftData error: \(error)")
        }
    }()
}

import SwiftUI
import SwiftData

// ❌ Old pattern with Core Data
struct OldTaskListView: View {
    @FetchRequest(
        sortDescriptors: [
            NSSortDescriptor(keyPath: \CDTask.createdAt, ascending: false)
        ],
        predicate: NSPredicate(format: "isCompleted == NO")
    )
    private var tasks: FetchedResults<CDTask>

    var body: some View {
        List(tasks) { task in
            Text(task.title)
        }
    }
}

// ✅ New pattern with SwiftData
struct NewTaskListView: View {
    // @Query with built-in sorting and filtering
    @Query(
        filter: #Predicate<Task> { !$0.isCompleted },
        sort: \Task.createdAt,
        order: .reverse
    )
    private var tasks: [Task]

    var body: some View {
        List(tasks) { task in
            TaskRowView(task: task)
        }
    }
}

struct TaskRowView: View {
    let task: Task

    var body: some View {
        HStack {
            // Priority indicator
            Circle()
                .fill(priorityColor)
                .frame(width: 8, height: 8)

            VStack(alignment: .leading) {
                Text(task.title)
                    .font(.headline)

                if let category = task.category {
                    Text(category.name)
                        .font(.caption)
                        .foregroundStyle(.secondary)
                }
            }

            Spacer()

            // Date badge
            Text(task.createdAt, style: .date)
                .font(.caption2)
                .foregroundStyle(.tertiary)
        }
    }

    private var priorityColor: Color {
        switch task.priority {
        case 3: return .red
        case 2: return .orange
        case 1: return .yellow
        default: return .gray
        }
    }
}

import SwiftUI
import SwiftData

// Solution 1: Use @Query with custom init
struct FilteredTasksView: View {
    @Query private var tasks: [Task]

    // Create view with specific filter
    init(showCompleted: Bool, categoryId: UUID?) {
        // Build predicate based on parameters
        var predicates: [Predicate<Task>] = []

        if !showCompleted {
            predicates.append(#Predicate { !$0.isCompleted })
        }

        if let categoryId {
            predicates.append(#Predicate { task in
                task.category?.id == categoryId
            })
        }

        // Combine predicates
        let combinedPredicate: Predicate<Task>?
        if predicates.isEmpty {
            combinedPredicate = nil
        } else if predicates.count == 1 {
            combinedPredicate = predicates[0]
        } else {
            // Manually combine for AND logic
            combinedPredicate = #Predicate<Task> { task in
                !task.isCompleted && task.category?.id == categoryId
            }
        }

        _tasks = Query(
            filter: combinedPredicate,
            sort: \Task.createdAt,
            order: .reverse
        )
    }

    var body: some View {
        List(tasks) { task in
            TaskRowView(task: task)
        }
    }
}

// Solution 2: View-side filtering with all results
struct SmartTaskListView: View {
    // Fetch all tasks
    @Query(sort: \Task.createdAt, order: .reverse)
    private var allTasks: [Task]

    // Filter state
    @State private var searchText = ""
    @State private var showCompleted = false
    @State private var selectedCategory: Category?

    // Computed filtering
    private var filteredTasks: [Task] {
        allTasks.filter { task in
            // Text filter
            let matchesSearch = searchText.isEmpty ||
                task.title.localizedCaseInsensitiveContains(searchText)

            // Status filter
            let matchesStatus = showCompleted || !task.isCompleted

            // Category filter
            let matchesCategory = selectedCategory == nil ||
                task.category?.id == selectedCategory?.id

            return matchesSearch && matchesStatus && matchesCategory
        }
    }

    var body: some View {
        NavigationStack {
            List(filteredTasks) { task in
                TaskRowView(task: task)
            }
            .searchable(text: $searchText)
            .toolbar {
                FilterMenu(
                    showCompleted: $showCompleted,
                    selectedCategory: $selectedCategory
                )
            }
        }
    }
}

import SwiftData

// Version 1: Initial schema
enum TaskSchemaV1: VersionedSchema {
    static var versionIdentifier = Schema.Version(1, 0, 0)

    static var models: [any PersistentModel.Type] {
        [Task.self, Category.self]
    }

    @Model
    final class Task {
        var id: UUID = UUID()
        var title: String = ""
        var isCompleted: Bool = false
        var createdAt: Date = Date()
        var category: Category?

        init(title: String) {
            self.title = title
        }
    }

    @Model
    final class Category {
        var id: UUID = UUID()
        var name: String = ""

        @Relationship(deleteRule: .cascade, inverse: \Task.category)
        var tasks: [Task] = []

        init(name: String) {
            self.name = name
        }
    }
}

// Version 2: Added priority and notes fields
enum TaskSchemaV2: VersionedSchema {
    static var versionIdentifier = Schema.Version(2, 0, 0)

    static var models: [any PersistentModel.Type] {
        [Task.self, Category.self]
    }

    @Model
    final class Task {
        var id: UUID = UUID()
        var title: String = ""
        var isCompleted: Bool = false
        var createdAt: Date = Date()
        // New properties with default values
        var priority: Int = 0
        var notes: String = ""
        var category: Category?

        init(title: String, priority: Int = 0) {
            self.title = title
            self.priority = priority
        }
    }

    @Model
    final class Category {
        var id: UUID = UUID()
        var name: String = ""
        // New property
        var color: String = "blue"

        @Relationship(deleteRule: .cascade, inverse: \Task.category)
        var tasks: [Task] = []

        init(name: String, color: String = "blue") {
            self.name = name
            self.color = color
        }
    }
}

import SwiftData

enum TaskMigrationPlan: SchemaMigrationPlan {
    // Chronological order of schemas
    static var schemas: [any VersionedSchema.Type] {
        [TaskSchemaV1.self, TaskSchemaV2.self]
    }

    // Migration stages
    static var stages: [MigrationStage] {
        [migrateV1toV2]
    }

    // V1 → V2 migration: lightweight (properties with defaults)
    static let migrateV1toV2 = MigrationStage.lightweight(
        fromVersion: TaskSchemaV1.self,
        toVersion: TaskSchemaV2.self
    )
}

// Container configuration with migration
@main
struct TaskManagerApp: App {
    var sharedModelContainer: ModelContainer = {
        do {
            return try ModelContainer(
                for: TaskSchemaV2.Task.self, TaskSchemaV2.Category.self,
                migrationPlan: TaskMigrationPlan.self
            )
        } catch {
            fatalError("Migration failed: \(error)")
        }
    }()

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .modelContainer(sharedModelContainer)
    }
}

import SwiftUI
import SwiftData

struct SectionedTaskListView: View {
    @Query(sort: \Task.createdAt, order: .reverse)
    private var tasks: [Task]

    // Grouping by category
    private var tasksByCategory: [(Category?, [Task])] {
        Dictionary(grouping: tasks) { $0.category }
            .map { ($0.key, $0.value) }
            .sorted { first, second in
                // Tasks without category last
                guard let firstName = first.0?.name else { return false }
                guard let secondName = second.0?.name else { return true }
                return firstName < secondName
            }
    }

    var body: some View {
        List {
            ForEach(tasksByCategory, id: \.0?.id) { category, categoryTasks in
                Section(header: SectionHeader(category: category)) {
                    ForEach(categoryTasks) { task in
                        TaskRowView(task: task)
                    }
                }
            }
        }
    }
}

struct SectionHeader: View {
    let category: Category?

    var body: some View {
        HStack {
            if let category {
                Circle()
                    .fill(Color(category.color))
                    .frame(width: 12, height: 12)
                Text(category.name)
            } else {
                Text("Uncategorized")
                    .foregroundStyle(.secondary)
            }
        }
    }
}

// Alternative: Grouping by date
struct DateGroupedTasksView: View {
    @Query(sort: \Task.createdAt, order: .reverse)
    private var tasks: [Task]

    private var tasksByDate: [(Date, [Task])] {
        let calendar = Calendar.current

        let grouped = Dictionary(grouping: tasks) { task in
            calendar.startOfDay(for: task.createdAt)
        }

        return grouped
            .map { ($0.key, $0.value) }
            .sorted { $0.0 > $1.0 }
    }

    var body: some View {
        List {
            ForEach(tasksByDate, id: \.0) { date, dateTasks in
                Section(header: Text(date, style: .date)) {
                    ForEach(dateTasks) { task in
                        TaskRowView(task: task)
                    }
                }
            }
        }
    }
}

import SwiftUI
import SwiftData

struct TaskManagementView: View {
    @Environment(\.modelContext) private var modelContext
    @Query private var tasks: [Task]
    @Query private var categories: [Category]

    @State private var newTaskTitle = ""
    @State private var selectedCategory: Category?

    var body: some View {
        NavigationStack {
            VStack {
                // Add form
                AddTaskForm(
                    title: $newTaskTitle,
                    category: $selectedCategory,
                    categories: categories,
                    onAdd: addTask
                )

                // Task list
                List {
                    ForEach(tasks) { task in
                        TaskRowView(task: task)
                            .swipeActions(edge: .trailing) {
                                Button(role: .destructive) {
                                    deleteTask(task)
                                } label: {
                                    Label("Delete", systemImage: "trash")
                                }
                            }
                            .swipeActions(edge: .leading) {
                                Button {
                                    toggleCompletion(task)
                                } label: {
                                    Label(
                                        task.isCompleted ? "Todo" : "Done",
                                        systemImage: task.isCompleted ? "circle" : "checkmark"
                                    )
                                }
                                .tint(task.isCompleted ? .orange : .green)
                            }
                    }
                }
            }
            .navigationTitle("Tasks")
        }
    }

    // CREATE
    private func addTask() {
        guard !newTaskTitle.isEmpty else { return }

        let task = Task(
            title: newTaskTitle,
            category: selectedCategory
        )

        // Insert into context
        modelContext.insert(task)

        // Explicit save (optional - autosave enabled by default)
        do {
            try modelContext.save()
        } catch {
            print("Save error: \(error)")
        }

        // Reset form
        newTaskTitle = ""
        selectedCategory = nil
    }

    // UPDATE
    private func toggleCompletion(_ task: Task) {
        // Direct modification - SwiftData tracks automatically
        task.isCompleted.toggle()

        // Automatic save handles persistence
    }

    // DELETE
    private func deleteTask(_ task: Task) {
        modelContext.delete(task)
    }
}

struct AddTaskForm: View {
    @Binding var title: String
    @Binding var category: Category?
    let categories: [Category]
    let onAdd: () -> Void

    var body: some View {
        VStack(spacing: 12) {
            TextField("New task...", text: $title)
                .textFieldStyle(.roundedBorder)

            HStack {
                Picker("Category", selection: $category) {
                    Text("None").tag(nil as Category?)
                    ForEach(categories) { cat in
                        Text(cat.name).tag(cat as Category?)
                    }
                }
                .pickerStyle(.menu)

                Button("Add", action: onAdd)
                    .buttonStyle(.borderedProminent)
                    .disabled(title.isEmpty)
            }
        }
        .padding()
    }
}

import XCTest
import SwiftData
@testable import TaskManager

final class TaskModelTests: XCTestCase {
    var container: ModelContainer!
    var context: ModelContext!

    override func setUpWithError() throws {
        // In-memory container for tests
        let config = ModelConfiguration(isStoredInMemoryOnly: true)
        container = try ModelContainer(
            for: Task.self, Category.self,
            configurations: config
        )
        context = ModelContext(container)
    }

    override func tearDownWithError() throws {
        container = nil
        context = nil
    }

    func testCreateTask() throws {
        // Given
        let task = Task(title: "Test Task")

        // When
        context.insert(task)
        try context.save()

        // Then
        let descriptor = FetchDescriptor<Task>()
        let tasks = try context.fetch(descriptor)

        XCTAssertEqual(tasks.count, 1)
        XCTAssertEqual(tasks.first?.title, "Test Task")
    }

    func testTaskCategoryRelationship() throws {
        // Given
        let category = Category(name: "Work", color: "blue")
        let task = Task(title: "Meeting", category: category)

        // When
        context.insert(category)
        context.insert(task)
        try context.save()

        // Then
        XCTAssertEqual(task.category?.name, "Work")
        XCTAssertTrue(category.tasks.contains(task))
    }

    func testDeleteCategoryCascade() throws {
        // Given
        let category = Category(name: "Personal")
        let task1 = Task(title: "Task 1", category: category)
        let task2 = Task(title: "Task 2", category: category)

        context.insert(category)
        context.insert(task1)
        context.insert(task2)
        try context.save()

        // When
        context.delete(category)
        try context.save()

        // Then - cascade delete should remove tasks
        let descriptor = FetchDescriptor<Task>()
        let remainingTasks = try context.fetch(descriptor)

        XCTAssertEqual(remainingTasks.count, 0)
    }

    func testFilteredFetch() throws {
        // Given
        let task1 = Task(title: "Completed", isCompleted: true)
        let task2 = Task(title: "Pending", isCompleted: false)
        let task3 = Task(title: "Also Pending", isCompleted: false)

        [task1, task2, task3].forEach { context.insert($0) }
        try context.save()

        // When
        var descriptor = FetchDescriptor<Task>(
            predicate: #Predicate { !$0.isCompleted }
        )
        let pendingTasks = try context.fetch(descriptor)

        // Then
        XCTAssertEqual(pendingTasks.count, 2)
    }
}

/*
 PHASE 1: PREPARATION
 □ Audit Core Data features in use
 □ Identify features not supported by SwiftData
 □ Create dedicated migration branch
 □ Back up test data

 PHASE 2: MODEL CONVERSION
 □ Convert NSManagedObject entities to @Model
 □ Adapt relationships with @Relationship
 □ Configure appropriate delete rules
 □ Add required default values

 PHASE 3: CONFIGURATION
 □ Create ModelContainer with existing store URL
 □ Configure versioned schema if needed
 □ Define migration plan
 □ Test in coexistence mode if applicable

 PHASE 4: CODE MIGRATION
 □ Replace @FetchRequest with @Query
 □ Adapt predicates to #Predicate
 □ Migrate NSFetchedResultsController to manual grouping
 □ Convert CRUD operations to ModelContext

 PHASE 5: VALIDATION
 □ Run all unit tests
 □ Test migration with real data
 □ Verify performance with Instruments
 □ Validate CloudKit sync (if applicable)

 PHASE 6: DEPLOYMENT
 □ Document breaking changes
 □ Prepare rollback plan
 □ Deploy to TestFlight
 □ Monitor post-deployment crashes
*/