I have 2 functions, one which should save the string to a CoreData attribute and another to fetch it. And this was written by copying working code from elsewhere in the project, so I can't figure out why when I print the contents of 'currentSetting' I get nil.
The save function is called from didSelectRowAtIndexPath and it sends in indexPath.row as the parameter and this fetches a String from an array.
func getImageSetting() {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Settings")
do {
let fetcher = try context.fetch(fetchRequest)
let data = fetcher as? [NSManagedObject]
if let results = data {
let settingResult = results[0]
currentSetting = settingResult.value(forKey: "imageQuality") as? String
print(currentSetting as Any)
} else { print ("error") }
}
catch let error as NSError {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
}
func saveSetting(selection: Int) {
let coreSelection = choices[selection]
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let itemEntity = NSEntityDescription.entity(forEntityName: "Settings", in: managedContext)!
let item = NSManagedObject(entity: itemEntity, insertInto: managedContext)
item.setValue(coreSelection, forKey: "imageQuality")
do {
try managedContext.save()
} catch let error as NSError {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
}
Related
I would like to remove all data from a selected Core Data Entity. I'm using the below code but getting the following error:
Unresolved identifier managedObjectContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserAccountTbl")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try managedObjectContext.executeRequest(batchDeleteRequest)
} catch {
// Error Handling
}
First of all – as already mentioned in the other answers – you have to get the NSManagedObjectContext from AppDelegate
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedObjectContext = appDelegate.persistentContainer.viewContext
Force unwrapping is perfectly fine, the application wouldn't even launch if AppDelegate was missing.
But there is a caveat:
If you call execute on the managed object context you have to merge the changes into the context because the execute operation doesn't modify the content of the context.
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserAccountTbl")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
batchDeleteRequest.resultType = .resultTypeObjectIDs
do {
let result = try managedObjectContext.execute(batchDeleteRequest) as! NSBatchDeleteResult
let changes = [NSDeletedObjectsKey : result.result as! [NSManagedObjectID]]
NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [managedObjectContext])
} catch {
print(error)
}
However you can avoid the merge step if you call execute on the persistent store coordinator
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserAccountTbl")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
let persistentStoreCoordinator = managedObjectContext.persistentStoreCoordinator!
try persistentStoreCoordinator.execute(batchDeleteRequest, with: managedObjectContext)
} catch {
print(error)
}
Seems like you haven't declared your managedObjectCotext and trying to access it. Try this:
let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserAccountTbl")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try managedObjectContext.executeRequest(batchDeleteRequest)
} catch {
// Error Handling
}
As from your error, you have not declare context from container which is in appDelegate. You can try with following code:
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
//We need to create a context from this container
let managedObjectContext = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "UserAccountTbl")
let batchDeleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try managedObjectContext.executeRequest(batchDeleteRequest)
} catch {
// Error Handling
}
My function below when called is not saving whatever is on the textfield to core data. When appearing in the debugg area what appears is "". THis code when used in the view did load function it does work but when I call it it does not work.
func timTebow(){
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Item", in: context)
let newUser = NSManagedObject(entity: entity!, insertInto: context)
newUser.setValue(playName.text, forKey: "atBATS")
do {
try context.save()
} catch {
print("Failed saving")
}
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Item")
request.returnsObjectsAsFaults = false
do {
let result = try context.fetch(request)
for data in result as! [NSManagedObject] {
print(data.value(forKey: "atBATS") as? String)
}
} catch {
print("Failed")
}
}
When I save to Core Data and then try to read from it, only the most recently saved value is retained.
The rest are nil when I try to print them out.
In my .xcdatamodeld, my entity is named CD_Cookbook and it has an attribute of name.
I'm not sure what I'm doing wrong.
func newCookbook(cookbook: String) {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "CD_Cookbook", in: managedContext)!
let item = NSManagedObject(entity: entity, insertInto: managedContext)
item.setValue(cookbook, forKey: "name")
do {
try managedContext.save()
}
catch {
print("did not save cookbook name to core data", error)
}
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "CD_Cookbook")
do {
let cd = try managedContext.fetch(fetchRequest)
print(cd)
}
catch {
print("Failed to fetch cookbook names from Core Data", error)
}
}
Instead of:
let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "CD_Cookbook")
Do this instead:
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "CD_Cookbook")
So I have this code which works fine, but I want a much better one.
func deleteCoreDataObjects() {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
//where groupData is an Array of an Entity
for i in 0..<self.groupData.count {
context.delete(groupData[i])
}
(UIApplication.shared.delegate as! AppDelegate).saveContext()
}
Currently I'm deleting the objects one by one via for loop.
You can try this:
func deleteAllData(entity: String)
{
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: entity)
fetchRequest.returnsObjectsAsFaults = false
do
{
let results = try managedContext.executeFetchRequest(fetchRequest)
for managedObject in results
{
let managedObjectData:NSManagedObject = managedObject as! NSManagedObject
managedContext.deleteObject(managedObjectData)
}
} catch let error as NSError {
print("Detele all data in \(entity) error : \(error) \(error.userInfo)")
}
}
Usage:
self.deleteAllData("your_entityName")
Already seen in: https://stackoverflow.com/a/33931528/2894160
Best is delete the persistence storage and then add new one instead of looping each entity (if you want to delete all entities from coredata).
func deletePersistentStoreCoordinator () {
do {
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("YourDatabaseName.sqlite")
try self.persistentStoreCoordinator.destroyPersistentStoreAtURL(url, withType: NSSQLiteStoreType, options: nil)
try self.persistentStoreCoordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
}
catch{
}
}
Here is the code for deleting records from Core Data :
//Delete user info from local db
func deleteUserInfo() {
let context = appdelegate.managedObjectContext
let coord = appdelegate.persistentStoreCoordinator
let fetchRequest = NSFetchRequest(entityName: "User")
if #available(iOS 9.0, *) {
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
//let predicate = NSPredicate(format: "id == %#", key)
//fetchRequest.predicate = predicate
do {
try coord.executeRequest(deleteRequest, withContext: context)
}
catch let error as NSError {
//Error handling
}
catch {}
} else {
// Fallback on earlier versions
do {
let users: NSArray = try appdelegate.managedObjectContext.executeFetchRequest(fetchRequest)
for user in users {
appdelegate.managedObjectContext.delete(user)
}
try appdelegate.managedObjectContext.save()
} catch let error as NSError {
//Error handling
}
catch {}
}
}
I have a list of categories that my user can choose. Since I am planning to add new categories without having to send a new update, I would like to load the new categories from my server every time a user launch the app. I came up with this code but every time it runs it keeps adding the same categories.
func loadDealCategory(){
let myUrl = NSURL(string: "\(ipAddress)/v1.0/dealCategory.php")
let request = NSMutableURLRequest(URL: myUrl!)
let task = NSURLSession.sharedSession().dataTaskWithRequest(request)
{ data, response, error in
if error != nil {
print("error\(error)")
}else{
do{
let json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) as! NSArray
let appDelegate =
UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
for jsonDictionary in json {
// listing of columns in JSON seed file
let categoryDescription = jsonDictionary.valueForKey("category_description") as! String
print(categoryDescription)
let newCategory = NSEntityDescription.insertNewObjectForEntityForName("Categories", inManagedObjectContext: managedContext)
newCategory.setValue(categoryDescription, forKey: "category_description")
// I tried also format: "category_description = %#"
let fetchRequest = NSFetchRequest(entityName: "Categories")
fetchRequest.predicate = NSPredicate(format: "category_description LIKE %#", categoryDescription)
do {
let fetchResults = try managedContext.executeFetchRequest(fetchRequest)
print(fetchResults)
if fetchResults.count == 0{
do {
try managedContext.save()
//5
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}
}else{
print("\(categoryDescription) already exist!")
}
} catch let error as NSError {
// failure
print("Fetch failed: \(error.localizedDescription)")
}
}
} catch{
print("something went wrong loading json")
}
}
}
task.resume()
}
is it ok , loading it in func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
Found the problem, I was inserting the object before checking if it was already in the entity.
if fetchResults.count == 0{
let newCategory = NSEntityDescription.insertNewObjectForEntityForName("Categories", inManagedObjectContext: managedContext)
newCategory.setValue(categoryDescription, forKey: "category_description")
}else{
print("Could not save \(error), \(error.userInfo)")
}
and only then save
do {
try managedContext.save()
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}