Preload database with CoreData, Swift 4 - ios

Question

I try to preload my database in my app (.sqlite, .sqlite-wal and .sqlite-shm), but I can't.
I try this:
func preloadDBData()
{
let sqlitePath = Bundle.main.path(forResource: "leksikonPreload", ofType: "sqlite")
let sqlitePath_shm = Bundle.main.path(forResource: "leksikonPreload", ofType: "sqlite-shm")
let sqlitePath_wal = Bundle.main.path(forResource: "leksikonPreload", ofType: "sqlite-wal")
let URL1 = URL(fileURLWithPath: sqlitePath!)
let URL2 = URL(fileURLWithPath: sqlitePath_shm!)
let URL3 = URL(fileURLWithPath: sqlitePath_wal!)
let URL4 = URL(fileURLWithPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/leksikonPreload.sqlite")
let URL5 = URL(fileURLWithPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/leksikonPreload.sqlite-shm")
let URL6 = URL(fileURLWithPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/leksikonPreload.sqlite-wal")
if !FileManager.default.fileExists(atPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/leksikonPreload.sqlite") {
// Copy 3 files
do {
try FileManager.default.copyItem(at: URL1, to: URL4)
try FileManager.default.copyItem(at: URL2, to: URL5)
try FileManager.default.copyItem(at: URL3, to: URL6)
print("=======================")
print("FILES COPIED")
print("=======================")
} catch {
print("=======================")
print("ERROR IN COPY OPERATION")
print("=======================")
}
} else {
print("=======================")
print("FILES EXIST")
print("=======================")
}
}
and call preloadDBData() in my appDelegate didFinishLaunchingWithOptions method. Name of my Core Data model: "leksikon", name of my preload data: "leksikonPreload". This func work fine and really write when "FILES COPYED" and "FILES EXIST", but when I try print my data - my array contain 0 elements, but I am sure, that leksikonPreload contains 12 values.
My code of print:
func printData() {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let fetchRequest: NSFetchRequest<Word> = Word.fetchRequest()
do
{
let arr = try context.fetch(fetchRequest)
for obj in arr {
print(obj.engValue)
print(obj.rusValue)
print(obj.was)
}
}
catch
{
print(error.localizedDescription)
}
}

Answer 1

I am having the same problem.
I have a preloadedDataBase called: BenedictusCoreData.sqlite
I added it to my project. And modified the AppDelegate:
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "BenedictusCoreData")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
// MARK: - Preload data from my sqlite file.
func preloadDBData() {
let sqlitePath = Bundle.main.path(forResource: "BenedictusCoreData", ofType: "sqlite")
let originURL = URL(fileURLWithPath: sqlitePath!)
let destinationURL = URL(fileURLWithPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/BenedictusCoreData.sqlite")
if !FileManager.default.fileExists(atPath: NSPersistentContainer.defaultDirectoryURL().relativePath + "/BenedictusCoreData.sqlite") {
// Copy file
do {
try FileManager.default.copyItem(at: originURL, to: destinationURL)
print("=======================")
print("FILE COPIED")
print("=======================")
} catch {
print("=======================")
print("ERROR IN COPY OPERATION")
print("=======================")
}
} else {
print("=======================")
print("FILE EXIST")
print("=======================")
}
}
I copied only the sqlite file because I have no wal and shm files and because I just want to copy the file the first time it is launched and only for reading purposes.
The preloadDBData() function is called in AppDelegate didFinishLaunchingWithOptions. And when launched for the first time says "FILE COPIED". And after it, when launched said "FILE EXIST". So it seems that the file is copied.
The model file in the project is called BenedictusCoreData.xcdatamodeld and the project name is BenedictusCoreData
And in the ViewController I wrote the following:
var encyclicalsArray = [Encyclicals]()
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
loadItems()
}
func loadItems() {
let request: NSFetchRequest<Encyclicals> = Encyclicals.fetchRequest()
do {
try encyclicalsArray = context.fetch(request)
for encyclical in encyclicalsArray {
print(encyclical.titulo_es!)
print(encyclical.date!)
print(encyclical.idURL!)
}
} catch {
print("Error fetching encyclicals: \(error)")
}
}
And it prints nothing. However, my sqlite preloaded file has three entries within this table.