【发布时间】：2016-06-02 09:10:59
【问题描述】：
我在使用private managedObjectContext在后台保存数据时遇到问题。我是 CoreData 的新手。我正在为NSManagedObjectContext 使用父子方法，但面临几个问题。
多次点击重新加载按钮时出现错误
错误：
'NSGenericException'，原因：集合 <__nscfset:> 在枚举时发生了变异
有时：在这里崩溃
try managedObjectContext.save()有时键值编码兼容错误
我的 ViewController 类
class ViewController: UIViewController {
var jsonObj:NSDictionary?
var values = [AnyObject]()
@IBOutlet weak var tableView:UITableView!
override func viewDidLoad() {
super.viewDidLoad()
getData()
saveInBD()
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.saved(_:)), name: "kContextSavedNotification", object: nil)
}
//Loding json data from a json file
func getData(){
if let path = NSBundle.mainBundle().pathForResource("countries", ofType: "json") {
do {
let data = try NSData(contentsOfURL: NSURL(fileURLWithPath: path), options: NSDataReadingOptions.DataReadingMappedIfSafe)
do {
jsonObj = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as? NSDictionary
} catch {
jsonObj = nil;
}
} catch let error as NSError {
print(error.localizedDescription)
}
} else {
print("Invalid filename/path.")
}
}
**Notification reciever**
func saved(not:NSNotification){
dispatch_async(dispatch_get_main_queue()) {
if let data = DatabaseManager.sharedInstance.getAllNews(){
self.values = data
print(data.count)
self.tableView.reloadData()
}
}
}
func saveInBD(){
if jsonObj != nil {
guard let nameArray = jsonObj?["data#"] as? NSArray else{return}
DatabaseManager.sharedInstance.addNewsInBackGround(nameArray)
}
}
//UIButton for re-saving data again
@IBAction func reloadAxn(sender: UIButton) {
saveInBD()
}
}
**Database Manager Class**
public class DatabaseManager{
static let sharedInstance = DatabaseManager()
let managedObjectContext = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
private init() {
}
func addNewsInBackGround(arr:NSArray) {
let jsonArray = arr
let moc = managedObjectContext
let privateMOC = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
privateMOC.parentContext = moc
privateMOC.performBlock {
for jsonObject in jsonArray {
let entity = NSEntityDescription.entityForName("Country",
inManagedObjectContext:privateMOC)
let managedObject = NSManagedObject(entity: entity!,
insertIntoManagedObjectContext: privateMOC) as! Country
managedObject.name = jsonObject.objectForKey("name")as? String
}
do {
try privateMOC.save()
self.saveMainContext()
NSNotificationCenter.defaultCenter().postNotificationName("kContextSavedNotification", object: nil)
} catch {
fatalError("Failure to save context: \(error)")
}
}
}
func getAllNews()->([AnyObject]?){
let fetchRequest = NSFetchRequest(entityName: "Country")
fetchRequest.resultType = NSFetchRequestResultType.DictionaryResultType
do {
let results =
try managedObjectContext.executeFetchRequest(fetchRequest)
results as? [NSDictionary]
if results.count > 0
{
return results
}else
{
return nil
}
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
return nil
}
}
func saveMainContext () {
if managedObjectContext.hasChanges {
do {
try managedObjectContext.save()
} catch {
let nserror = error as NSError
print("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}
}
【问题讨论】：
标签： ios swift core-data concurrency nsmanagedobjectcontext