Reputation: 133
I am trying to create a simple task to-do application with swiftui and core-data however, I am running into some problems when adding views. I have a TaskView
view that will be used to show some info about the task within the list (title, date, etc.). However, when trying to create a preview for the view with a demo Task
object the preview crashes (running app still works).
Sorry if this is a trivial question, new to swift and programming in general.
TaskView.swift
import SwiftUI
struct TaskView: View {
@Environment(\.managedObjectContext) var managedObjectContext
var task: Task
var body: some View {
HStack {
Image(systemName: task.checked == true ? "circle" : "checkmark.circle.fill")
VStack {
Text(task.name ?? "unknown name")
Text(String(task.streak))
}
}
}
}
struct TaskView_Previews: PreviewProvider {
static var previews: some View {
let task = Task()
task.name = "Washing up"
task.desc = "Wash the dishes"
task.checked = false
task.streak = 2
return TaskView(task: task)
.previewLayout(.fixed(width: 375, height: 60))
}
}
ContentView.swift
import SwiftUI
struct ContentView: View {
@Environment(\.managedObjectContext) var managedObjectContext
@FetchRequest(entity: Task.entity(), sortDescriptors: [
NSSortDescriptor(keyPath: \Task.checked, ascending: false),
NSSortDescriptor(keyPath: \Task.name, ascending: true)
]) var tasks: FetchedResults<Task>
var body: some View {
NavigationView {
List {
ForEach(tasks, id: \.self) { task in
TaskView(task: task).environment(\.managedObjectContext, self.managedObjectContext)
}
.onDelete(perform: deleteTask)
}
.navigationBarTitle("Today")
}
}
func deleteTask(at indexSet: IndexSet) {
indexSet.forEach { TaskUtils.delete(task: tasks[$0], using: self.managedObjectContext)}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
Upvotes: 1
Views: 119
Reputation: 166
I fixed your TaskView by adding first setting a context constant and then using init in initialising the task constant that you are using in the preview
import SwiftUI
struct TaskView: View {
@Environment(\.managedObjectContext) var managedObjectContext
var task: Task
var body: some View {
HStack {
Image(systemName: task.checked == true ? "circle" : "checkmark.circle.fill")
VStack {
Text(task.name ?? "unknown name")
Text(String(task.streak))
}
}
}
}
struct TaskView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext // IMPORTANT
let task = Task.init(context: context) // IMPORTANT
task.name = "Washing up"
task.desc = "Wash the dishes"
task.checked = false
task.streak = 2
return TaskView(task: task).environment(\.managedObjectContext, context)
.previewLayout(.fixed(width: 375, height: 60))
}
}
As for your ContentView, I made minor changes to get it working- added a button to add objects to the CoreData model.
import SwiftUI
struct ContentView: View {
@Environment(\.managedObjectContext) var managedObjectContext
@FetchRequest(entity: Task.entity(), sortDescriptors: [
NSSortDescriptor(keyPath: \Task.checked, ascending: false),
NSSortDescriptor(keyPath: \Task.name, ascending: true)
]) var tasks: FetchedResults<Task>
var body: some View {
NavigationView {
List {
ForEach(tasks, id: \.self) { task in
TaskView(task: task).environment(\.managedObjectContext, self.managedObjectContext)
}
//.onDelete(perform: deleteTask)
}
.navigationBarTitle("Today")
.navigationBarItems(trailing:
Button("Add") {
let task = Task(context: self.managedObjectContext)
task.name = "Washing up"
task.desc = "Wash the dishes"
task.checked = false
task.streak = Int32(Int.random(in: 0...10))
try? self.managedObjectContext.save()
}
)
}
}
// func deleteTask(at indexSet: IndexSet) {
// indexSet.forEach { TaskUtils.delete(task: tasks[$0], using: self.managedObjectContext)}
// }
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return ContentView().environment(\.managedObjectContext, context)
}
}
Upvotes: 1