Loading saved context from AppDelegate to another ViewController - ios

Question

I'm trying to make an array from my Viewcontroller equal to, the objects my core data has saved. I'm using core data and created an entity named Pokemon which has 3 attributes name, id and generation. In the app delegate, I use the following function to get Pokemon from this API. This is what I do to parse the data and save the context:
typealias DownloadCompleted = () -> ()
var pokemonId: Int16 = 0
func fetchPokemon(url: String, completed: #escaping DownloadCompleted) {
let context = coreData.persistentContainer.viewContext
let url = URLRequest(url: URL(string: url)!)
let task = URLSession.shared.dataTask(with: url) { (data, repsonse, error) in
if error != nil {
print(error!)
}
do {
let jsonResult = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as! NSDictionary
let jsonArray = jsonResult.value(forKey: "results") as! [[String: Any]]
for pokemonData in jsonArray {
self.pokemonId += 1
if self.pokemonId > 721 {
self.coreData.saveContext()
return
}
guard let name = pokemonData["name"] as? String else {
return
}
let pokemon = Pokemon(context: context)
pokemon.name = name
pokemon.id = self.pokemonId
print("Name: \(pokemon.name) Id:\(self.pokemonId)")
if self.pokemonId <= 151 {
pokemon.generation = 1
} else if self.pokemonId <= 251 {
pokemon.generation = 2
} else if self.pokemonId <= 386 {
pokemon.generation = 3
} else if self.pokemonId <= 493 {
pokemon.generation = 4
} else if self.pokemonId <= 649 {
pokemon.generation = 5
} else if self.pokemonId <= 721 {
pokemon.generation = 6
}
}
guard let nextURL = jsonResult.value(forKey: "next") as? String else {
self.coreData.saveContext()
return
}
DispatchQueue.main.async {
self.fetchPokemon(url: nextURL, completed: {
self.coreData.saveContext()
})
completed()
}
} catch let err {
print(err.localizedDescription)
}
}
task.resume()
}
This is how I call it in the appDelegate. Really don't know what to do in the middle of the fetchPokemon or how to call it in another view controller. So I left it blank, not sure if this has something to do with the problem I'm having.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let context = self.coreData.persistentContainer.viewContext
let pokemonListVC = self.window?.rootViewController as! PokemonListVC
pokemonListVC.context = context
fetchPokemon(url: pokemonAPI) {
}
return true
}
Im using this SQL-Light read-only app from the app store. I check the data and all 721 pokemon are saving. Now, I don't know how I would be able to make the array in my view controller equal to all 721 Pokemon saved. I added this code into my viewController.
class PokemonListVC: UIViewController {
weak var context: NSManagedObjectContext! {
didSet {
return pokemon = Pokemon(context: context)
}
}
var pokemon: Pokemon? = nil
lazy var pokemons = [Pokemon]()
override func viewDidLoad() {
super.viewDidLoad()
loadData()
}
func loadData() {
pokemons = pokemon!.loadPokemon(generation: 1, context: context)
}
}
I've created an extension of my Pokemon entity and added a function loadPokemon that filters the Pokemon by generation. Here is the code.
extension Pokemon {
func loadPokemon(generation: Int16 = 0, context: NSManagedObjectContext) -> [Pokemon] {
let request: NSFetchRequest<Pokemon> = Pokemon.fetchRequest()
request.predicate = NSPredicate(format: "generation = %#", generation)
request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
do {
let pokemons = try context.fetch(request)
print("My Pokemon count: \(pokemons.count)")
return pokemons
} catch let err {
print(err.localizedDescription)
}
return []
}
}
When I call the loadData in my ViewController it crashes. The array count is 0 and so is the one in the hero extension. So I don't how to make my array equal the Pokemon saved from coreData.
Would really appreciate any help provided. :)
Here is my deleteRecords code, which is also in my appDelegate. This deletes all records when app launches. I call this method at the very beginning of didFinishLaunchingWithOption function before the fetchPokemons.
func deleteRecords() {
let context = coreData.persistentContainer.viewContext
let pokemonRequest: NSFetchRequest<Pokemon> = Pokemon.fetchRequest()
var deleteRequest: NSBatchDeleteRequest
var deleteResults: NSPersistentStoreResult
do {
deleteRequest = NSBatchDeleteRequest(fetchRequest: pokemonRequest as! NSFetchRequest<NSFetchRequestResult>)
deleteResults = try context.execute(deleteRequest)
} catch let err {
print(err.localizedDescription)
}
}

Answer 1

As you are saying that you have sure that all the pockemon records are stored correctly in your coredata you can simply fetch records from your codedata by providing fetch request. I have created demo for contact storing and I can get all the contact by this fetch request you can try this code in your ViewController where you want to fetch all the record.
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSManagedObject> (entityName: "Pokemon")
do {
arrPockemon = try managedContext.fetch(fetchRequest)
}catch let error as NSError {
showAlert(string: error.localizedDescription)
}
try to get all records first and if you get all then work for filtering extension and all. hope it will help you. you can learn from here https://code.tutsplus.com/tutorials/core-data-and-swift-core-data-stack--cms-25065
save flag on userDefault.
//check for first time when app is installed first time(first time flag is not present so)
let userDefault = UserDefaults.standard.dictionaryRepresentation()
if userDefault.keys.contains("isDataAvailable") {
//key is availebe so check it
if userDefault["isDataAvailable"] as! String == "1"{
//no need to call server for data
}else{
//fetch data from server
// once you get data from server make isDataAvailable flage as 1
UserDefaults.standard.setValue("1", forKey: "isDataAvailable")
UserDefaults.standard.synchronize()
}
}
else{
//flag is not avalable so call server for data
// once you get data from server make isDataAvailable flage as 1
UserDefaults.standard.setValue("1", forKey: "isDataAvailable")
UserDefaults.standard.synchronize()
}