脚本在VC中我通过导航项目上的左键调用。
问题：
你能帮助我解释一下原因：如果我使用var productToCheck = Product() func工作填充数组，但我得到了Failed to call designated initializer on NSManagedObject class消息。相反，如果我应用var productToCheck = NSEntityDescription.insertNewObject(forEntityName: self.kProductEntityName, into: managedContext) as! Product
错误消失但VC出现时，在控制台上第一次显示产品的名称，但如果我在根VC和此VC之间来回，则在控制台上显示比产品名称更“未知”。
thanx
// MARK: - async fetch request 1
var asyncFetchRequest: NSAsynchronousFetchRequest<Product>!
var asyncProductsArray : [NSManagedObject] = []
//MARK: - CoreData properties
var managedContext: NSManagedObjectContext!
let kProductEntityName = "Product"
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
makeAsyncFetch()
//end viewWillAppear
}
func makeAsyncFetch() {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
let managedContext = appDelegate.persistentContainer.viewContext
// MARK: - async fetch request 2
let productFetch = NSFetchRequest<Product>(entityName: kProductEntityName)
asyncFetchRequest = NSAsynchronousFetchRequest<Product>(fetchRequest: productFetch) {
[unowned self] (result: NSAsynchronousFetchResult) in
guard let AllProductResult = result.finalResult else {
return
}
self.asyncProductsArray = AllProductResult
//********************* issue start **************************
for singleProduct in self.asyncProductsArray {
//thisbelow causes "Failed to call designated initializer on NSManagedObject class" message, but no data repeated in console
//var productToCheck = Product()
//this below silcences "Failed to call designated initializer on NSManagedObject class" message but causes "repeating" issue
// var productToCheck = NSEntityDescription.insertNewObject(forEntityName: self.kProductEntityName, into: managedContext) as! Product
productToCheck = singleProduct as! Product
//since the second time this VC appears, "name" printed but also "unknown", each time once more than before
print(productToCheck.name ?? "unknown")
}
//********************* issue ends **************************
}
// MARK: - async fetch request 3
do {
try managedContext.execute(asyncFetchRequest)
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
}
UPADTE
这是我用来添加测试实体的脚本
//MARK: - reading csv
//I read and clear the rows
var data = readDataFromCSV(fileName: kCSVFileName, fileType: kCSVFileExtension)
data = cleanRows(file: data!)
let csvRows = csv(data: data!)
//with this I make more cler wich index I'm using
enum columnsProd : Int {
case productId = 0
case name = 1
case category = 2
case priceForCustomer = 3
case priceForRetail = 4
case quantity = 5
case total = 6
}
//with this FOR loop below, I can have an index number and the ENTIRE element at that index, in this case is another array I can search in
//I use dropFirst() in order to skip the first (n°) rows
for (_/*index*/, element) in csvRows.dropFirst(2).enumerated() {
//here I skip all the result that match the if:
if element[columnsProd.productId.rawValue] != "" && !element[columnsProd.name.rawValue].contains("ORDINE SEPARATO") && !element[columnsProd.name.rawValue].contains("Gift Card") {
var myFutureEntityInstance = myFutureEntity()
var productIdentification = element[columnsProd.productId.rawValue]
if productIdentification == "" {productIdentification = "unknown"; }
var nameFromSingleRow = element[columnsProd.name.rawValue]
if nameFromSingleRow == "" {nameFromSingleRow = "unknown"}
var elementCAtegory = element[columnsProd.category.rawValue] //was a date for differnt class
if elementCAtegory == "" {elementCAtegory = "unknown"}
var thePriceCustomer = element[columnsProd.priceForCustomer.rawValue]
if thePriceCustomer == "" {thePriceCustomer = "unknown"}
var thePriceRetailer = element[columnsProd.priceForRetail.rawValue]
if thePriceRetailer == "" {thePriceRetailer = "unknown"}
myFutureEntityInstance.productName = nameFromSingleRow
myFutureEntityInstance.productProdId = productIdentification
myFutureEntityInstance.productCategory = elementCAtegory
myFutureEntityInstance.productPriceCustomer = thePriceCustomer
myFutureEntityInstance.productPriceRetailer = thePriceRetailer
//here for avoid duplicates with same name
self.productNameArray.append(nameFromSingleRow)
// here only for a test in wich I
// if nameFromSingleRow == "Item Name" {
// addTheItemToCoreData(futureEntity: myFutureEntityInstance)
// print("added")
// }
//I fill an array with struct tha has the same structure of the future Entity
self.asyncTempItemArray.append(myFutureEntityInstance)
}
}
func起诉添加项目
func addTheItemToCoreData(futureEntity : myFutureEntity) {
//this func should be used to update the internal entitylist where only if a item is not present will be put to be shown in the list, tha0ts why each item is by default not present in collection
//CoreData : appDelegte + managedContext
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: self.kItemEntityName, in: managedContext)!
let itemToAdd = Item(entity: entity, insertInto: managedContext)
itemToAdd.product_id = futureEntity.itemProdId
itemToAdd.category = futureEntity.itemCategory
itemToAdd.name = futureEntity.itemName
itemToAdd.inMyCollection = false
itemToAdd.inWishlist = false
// itemToAdd.priceCustomer = Double(futureEntity.itemPriceCustomer!)!
// itemToAdd.priceRecommended = Double(futureEntity.itemPriceRetailer!)!
do {
try managedContext.save()
} catch let error as NSError {
print("could not save. \(error), \(error.userInfo)")
}
}