限定Bundle.main.url使用核心数据为iOS9和上述夫特4

Question

I'm just learning Core Data and I need to implement Core Data for both iOS 9 and iOS 10 as my only iPad test device is an iPad3 running iOS 9.3.5 . I'm trying to follow this solution https://charleswilson.blog/2016/09/09/out-of-context-using-core-data-on-ios-9-3-and-10-0/ ( not sure I could paste the whole code from the link ) as I failed with implementing other solutions from stack overflow. I'm not sure If I got this one thing right: Inside the lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator there is this let modelURL = Bundle.main.url(forResource: modelName, withExtension: modelExtension)! that I see in other solutions here in stack overflow and they're all declared as with different String values for forResource parameter, but all with the same "momd" value for withExtension: parameter. I actually thought the since I'm using an .xcdatamodeld I should put in my data model name for forResource parameter and "xcdatamodeld" for withExtension: parameter, resulting in my case as :

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
        let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
        let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        let url = self.applicationDocumentsDirectory.appendingPathComponent("fix_it_shop").appendingPathExtension("xcdatamodeld")

        do {
            try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
        } catch {
            let dict : [String : Any] = [NSLocalizedDescriptionKey        : "Failed to initialize the application's saved data" as NSString,
                                         NSLocalizedFailureReasonErrorKey : "There was an error creating or loading the application's saved data." as NSString,
                                         NSUnderlyingErrorKey             : error as NSError]

            let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
            fatalError("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        }

        return coordinator
    }()

Is it so or withExtension: parameter is unrelated to my xcdatamodeld file extension and I should use "momd" instead? Similar questions I found point me in both directions. Many thanks for any explanation you could give about it.

Answer 1

You should use “momd” as the file extension for the model. During the Xcode compilation process, your .xcdatamodeld file gets compiled into a .momd file, which is what actually gets included in the bundle.

However, the url variable in the persistentStoreCoordinator definition refers to the NSPersistentStore file, which for a sqlite store will have the extension “.sqlite”.