获取核心数据字符串并放置在标签中(Swift4)

Question

我试图调用两个不同的核心数据字符串，并将它们分别放在不同的标签上。现在我收到错误。无法使用类型为"([NSManagedObject]("的参数列表调用类型为"init(_：("的初始值设定项。此错误来自j1.text=String(itemsName(。我添加了用于保存和显示的两个视图控制器。

import UIKit
import CoreData
class ViewController: UIViewController {
@IBOutlet var j1 : UITextField!
@IBOutlet var j2 : UITextField!

@IBAction func save(){
let appD = UIApplication.shared.delegate as! AppDelegate
let context = appD.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Team", in : context)!
let theTitle = NSManagedObject(entity: entity, insertInto: context)
theTitle.setValue(j1.text, forKey: "score")
theTitle.setValue(j2.text, forKey: "alba")

do {
try context.save()
}
catch {
print("Tom Corley")
}
}}
class twoVC: UIViewController {
@IBOutlet var j1 : UILabel!
@IBOutlet var j2 : UILabel!
var itemsName : [NSManagedObject] = []
var itemsName2 : [NSManagedObject] = []
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let appD = UIApplication.shared.delegate as! AppDelegate
let context = appD.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Team")
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "score", ascending: true)]

let fetchRequest2 = NSFetchRequest<NSManagedObject>(entityName: "Team")
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "alba", ascending: true)]


do {
itemsName = try context.fetch(fetchRequest)
itemsName2 = try context.fetch(fetchRequest2)
if let score = itemsName[0].value(forKey: "score") {
j1.text = (score as! String)
}
if let alba = itemsName2[0].value(forKey: "alba") {
j2.text = (alba as? String)
}

}catch {
print("Ashley Tisdale")
}
}}

Answer 1

对提取的结果进行循环，并将其附加到一个字符串中，该字符串随后用作标签的值，这将进入今天进行提取的do{...}中。请注意，我在这里只使用了一个获取请求。

itemsName = try context.fetch(fetchRequest)
var mergedScore: String = ""
var mergedAlba: String = ""
for item in itemsName {
if let score = item.value(forKey: "score") as? String {
mergedScore.append(score)
mergedScore.append(" ") //separator
}
if let alba = item.value(forKey: "alba") as? String {
mergedScore.append(alba)
mergedScore.append(" ") //separator
}
}
j1.text = mergedScore
j2.text = mergedAlba

Answer 2

试试这个吧，它对我来说很有用Swift 4我认为你需要将值存储为int，用作sortDDescriptor。

func FetchManagedObjectFromDatabaseForStoreData(Entity :NSEntityDescription) -> 
[NSManagedObject]
{
let fetchRequest = NSFetchRequest<NSFetchRequestResult>()
// Add Sort Descriptor
let sortDescriptor = NSSortDescriptor(key: "order", ascending: true)
let sortDescriptor1 = NSSortDescriptor(key: "is_favourite", ascending: false)
fetchRequest.sortDescriptors = [sortDescriptor,sortDescriptor1]
// Create Entity Description
fetchRequest.entity = Entity
let result : [NSManagedObject] = []
// Execute Fetch Request
do{
let result = try appDelegate.managedObjectContext.fetch(fetchRequest) as! [NSManagedObject]
if  result.count > 0
{
return result
}
else
{
// return result
}
}
catch{
let fetchError = error as NSError
print(fetchError)
}
return result
}

用于提取数据

// Create Entity Description
let entityDescription = NSEntityDescription.entity(forEntityName: "Your Entity Name Here", in: appDel.managedObjectContext)
let DataObject = FetchManagedObjectFromDatabaseForStoreData(Entity: entityDescription!)
//Convert  Array of NSManagedObject into array of [String:AnyObject]     
for item in DataObject{
let keys = Array(item.entity.attributesByName.keys)
// Here is your result
print((item.dictionaryWithValues(forKeys: keys) as NSDictionary).value(forKey: "id") as Any) // And so On Whatewer you Fetch
}