AppDelegate.Swift compile error after updating to Swift 5-CodePudding

I recently updated a project after not touching it for a year or two, and now I'm having some issues.

Everything worked before and I even went thru each error to update the new syntax, but I'm stuck at one function in AppDelegate.Swift that's preventing me from running the program. It's this one here:

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = Bundle.mainBundle.url(forResource: "ProjectName", withExtension: "momd")
    return NSManagedObjectModel(contentsOfURL: modelURL ?? <#default value#>)!
}()

After I take the suggestions from Xcode and update the Syntax it looks like this:

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = Bundle.main.url(forResource: "ProjectName", withExtension: "momd")
    return NSManagedObjectModel(contentsOf: modelURL ?? <#default value#>)!
}()

I'm really confused as to what to put for the default value as I've never edited or touched AppDelegate before. What do I need to put here?

Thank you for any help you may provide!

CodePudding user response：

As the application doesn't work at all if the model is missing you can force unwrap the URL

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = Bundle.main.url(forResource: "ProjectName", withExtension: "momd")!
    return NSManagedObjectModel(contentsOf: modelURL)!
}()

Consider that since iOS 10, macOS 10.12 there is a more convenient way to initialize the Core Data stack with NSPersistentContainer