SwiftUI Preview canvas and Core Data

Question

Preview canvas is is crashing but in simulator everything working fine. I assuming it related to @ObservedObject and @Fetchrequest...

tried solution for here Preview

Answer 1

So, if you put some code in an onAppear handler in the preview, it will run on boot. It even live updates as you type!

struct TemplateEditor_Previews: PreviewProvider {
  static var previews: some View {
    TemplateEditor().environment(\.managedObjectContext, AppDelegate.viewContext).onAppear {
      let entity = GlobalPlaceholders(context: AppDelegate.viewContext)
      entity.name = "abc123"

      // Or create more, if you need more example data

      try! AppDelegate.viewContext.save()
    }
  }
}

Note that I've wrapped up my viewContext in a static method on AppDelegate to make access a tiny bit less verbose and easier to remember:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  static var persistentContainer: NSPersistentContainer {
    return (UIApplication.shared.delegate as! AppDelegate).persistentContainer
  }

  static var viewContext: NSManagedObjectContext {
    return persistentContainer.viewContext
  }