Within the earlier tutorial, I’ve walked you thru the fundamentals of SwiftData, a brand new framework launched in iOS 17 as a substitute for Core Information. You probably have adopted that tutorial, it is best to now be conversant in utilizing SwiftData to save lots of and handle knowledge in a database. The built-in @Mannequin macro and the @Question macro tremendously simplify the method of defining knowledge mannequin and retrieving data from the database, making it extraordinarily straightforward for builders to deal with persistent knowledge.
The Preview function in SwiftUI is very useful because it permits builders to immediately visualize the app’s consumer interface with out the necessity to launch the simulator. Nevertheless, utilizing SwiftData with SwiftUI Preview requires some extra steps. On this tutorial, we are going to discover easy methods to combine SwiftData with SwiftUI Preview successfully.
Observe: When you haven’t learn the SwiftData tutorial, I extremely suggest checking it out first, as this tutorial references a few of the supplies lined in that tutorial.
Revisiting the Information Mannequin and SwiftData
Within the earlier instance, we now have constructed a mannequin class for ToDoItem like this:
import Basis
import SwiftData
@Mannequin class ToDoItem: Identifiable {
var id: UUID
var identify: String
var isComplete: Bool
init(id: UUID = UUID(), identify: String = "", isComplete: Bool = false) {
self.id = id
self.identify = identify
self.isComplete = isComplete
}
}SwiftData simplifies the method of defining a schema utilizing code. You solely have to mark the mannequin class with the @Mannequin macro. SwiftData will then robotically allow persistence for the info class.
So as to drive the info operations (like replace, insert, learn, and delete), we additionally have to arrange the mannequin container. Within the ToDoDemoAppApp.swift, we now have hooked up the modelContainer modifier like beneath:
struct ToDoDemoAppApp: App {
var physique: some Scene {
WindowGroup {
ContentView()
}
.modelContainer(for: ToDoItem.self)
}
}This configuration is basically all you want earlier than beginning to work with SwiftData.
Preview with SwiftData and In-memory Container
Within the Todo app demo, we now have a ContentView that masses and shows the to-do merchandise within the record view. Right here is the pattern code:
struct ContentView: View {
@Atmosphere(.modelContext) non-public var modelContext
@Question var todoItems: [ToDoItem]
var physique: some View {
NavigationStack {
Checklist {
ForEach(todoItems) { todoItem in
HStack {
Textual content(todoItem.identify)
Spacer()
if todoItem.isComplete {
Picture(systemName: "checkmark")
}
}
}
}
.navigationTitle("To Do Checklist")
}
}
}You can also make the preview work by writing the preview code like this:
#Preview {
ContentView()
.modelContainer(for: ToDoItem.self)
}Nevertheless, on this case, the preview solely shows an empty Todo record as a result of the container doesn’t have any knowledge populated. When you need to have some pattern knowledge, you’ll be able to create a customized mannequin container particularly for the preview. Right here is an instance:
@MainActor
let previewContainer: ModelContainer = {
do {
let container = strive ModelContainer(for: ToDoItem.self,
configurations: .init(isStoredInMemoryOnly: true))
for _ in 1...10 {
container.mainContext.insert(generateRandomTodoItem())
}
return container
} catch {
fatalError("Didn't create container")
}
}()
func generateRandomTodoItem() -> ToDoItem {
let duties = [ "Buy groceries", "Finish homework", "Go for a run", "Practice Yoga", "Read a book", "Write a blog post", "Clean the house", "Walk the dog", "Attend a meeting" ]
let randomIndex = Int.random(in: 0..We instantiate a ModelContainer with an in-memory configuration and populate the container with 10 random to-do gadgets. To make use of this preview container, you merely modify the preview code and specify to make use of the previewContainer:
#Preview {
ContentView()
.modelContainer(previewContainer)
}When you made the modification, the preview pane ought to present you the Todo record view with 10 random gadgets.
Abstract
SwiftUI Preview is a useful function that enables builders to visualise their app’s consumer interface immediately, with out the necessity to launch the simulator. This tutorial supplies complete steering on successfully utilizing SwiftData with SwiftUI Preview. You must learn to create a customized container populated with pattern knowledge particularly for preview functions.
When you get pleasure from studying this tutorial and wish to be taught extra about SwiftUI, don’t overlook to take a look at our Mastering SwiftUI e book for iOS 17 and Xcode 15.
