I want to load more cells when user in the last cell. I use CoreData and I get data from it. I use this answer to do what I want, but it didn't work. What problem can be there? Also I have one more question. I don't know why working only first implementation.
First implementation
var fetchedResultsController: NSFetchedResultsController {
let moc = DatabaseController.sharedInstance.managedObjectContext
let fetchRequest = NSFetchRequest()
let entity = NSEntityDescription.entityForName("Coctail", inManagedObjectContext: moc)
fetchRequest.entity = entity
fetchRequest.fetchLimit = 10
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,
managedObjectContext: moc,
sectionNameKeyPath: nil,
cacheName: nil)
aFetchedResultsController.delegate = self
do {
try aFetchedResultsController.performFetch()
} catch {
fatalError("\(error)")
}
return aFetchedResultsController
}
Second Implementation
func initilizeFetchedResultsController() {
let moc = DatabaseController.sharedInstance.managedObjectContext
let fetchRequest = NSFetchRequest()
let entity = NSEntityDescription.entityForName("Coctail", inManagedObjectContext: moc)
fetchRequest.entity = entity
fetchRequest.fetchLimit = 10
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest,
managedObjectContext: moc,
sectionNameKeyPath: nil,
cacheName: nil)
aFetchedResultsController.delegate = self
do {
try aFetchedResultsController.performFetch()
} catch {
fatalError("\(error)")
}
fetchedResultsController = aFetchedResultsController
}
Hard to tell why the first solution but the second doesn't without seeing the other code that would have used the fetchedResultsController or called initilizeFetchedResultsController().
The reason you're not getting more data is that you've hardcoded your fetchLimit to 10. No matter what you do, you'll only ever get 10 results.
You'll need to change the fetchLimit to get more data. Check out this answer -- it is similar to what you'll need to do: https://stackoverflow.com/a/6786931/5605379
Related
No matter what I put as the value in sectionNameKeyPath: "value", the fetched objects get returned in the order in which they were saved in the database. The number of sections is correct, but whether I view the fetched objects by section fetchedResultsController.sections or fetchedResultsController.object(at: indexPath) I get the same results.
This is in the UITableViewController
lazy var fetchedResultsController: NSFetchedResultsController<Dice> = {
let fetchRequest: NSFetchRequest<Dice> = Dice.fetchRequest()
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "createdAt", ascending: false)]
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let context = appDelegate.persistentContainer.viewContext
// Doesn't matter what I set in the "sectionNameKeyPath" value
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: "set.identifier", cacheName: nil)
fetchedResultsController.delegate = self
return fetchedResultsController
}()
Has anyone else seen this?
I was using a lazy var in table view controller to get the data from CoreData. It was working good in swift2. But When I upgraded to Swift3, Its showing an error as below. Kindly help me to change for Swift3
Error : Cannot convert value of type 'Error' to specified type 'NSFetchedResultsController'
lazy var fetchedResultsController: NSfetchedResultsController =
{
let fetchRequest = NSFetchRequest(entityName: "EvtIvtTbl")
let sortDescriptor = NSSortDescriptor(key: "bym_kol", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
let fetchedResultsController = NSfetchedResultsController(fetchRequest: fetchRequest,
managedObjectContext: self.managedObjectContext,
sectionNameKeyPath: nil,
cacheName: nil)
fetchedResultsController.delegate = self
return fetchedResultsController
}()
In Swift 3.0, NSFetchedResultsController and NSFetchRequest want type parameters. Assuming that EvtIvtTbl is your NSManagedObject subclass, your code should look like this:
lazy var fetchedResultsController: NSFetchedResultsController<EvtIvtTbl> = {
let fetchRequest = NSFetchRequest<EvtIvtTbl>(entityName: "EvtIvtTbl")
let sortDescriptor = NSSortDescriptor(key: "bym_kol", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
let fetchedResultsController = NSFetchedResultsController<EvtIvtTbl>(fetchRequest: fetchRequest,
managedObjectContext: self.managedObjectContext,
sectionNameKeyPath: nil,
cacheName: nil)
fetchedResultsController.delegate = self
return fetchedResultsController
}()
how can I convert my NSFetchedResultsController to swift 3.0, i can't get it to work.... I tried apple's auto conversion but it's not working??
I had this:
lazy var fetchedResultsControler: NSFetchedResultsController = {
let fetchRequest = NSFetchRequest(entityName: "Mesages")
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "timestamp", ascending: true)]
fetchRequest.predicate = NSPredicate(format: "user.id = %#", self.friend!.id!)
let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
let frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)
frc.delegate = self
return frc
}()
automatically converted to this:
lazy var fetchedResultsControler: NSFetchedResultsController = { () -> <<error type>> in
let fetchRequest = NSFetchRequest(entityName: "Mesages")
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "timestamp", ascending: true)]
fetchRequest.predicate = NSPredicate(format: "user.id = %#", self.friend!.id!)
let moc = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
let frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)
frc.delegate = self
return frc
}()
but It's not working, it's asking me to put semi colons in random places
It is needed to set up NSFetchRequestResult inside brackets <>.
For swift 3.0:
lazy var fetchedResultsControler: NSFetchedResultsController<NSFetchRequestResult> = {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Mesages")
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "timestamp", ascending: true)]
fetchRequest.predicate = NSPredicate(format: "user.id = %#", self.friend!.id!)
let moc = (UIApplication.shared.delegate as! AppDelegate).managedObjectContext
let frc = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: moc, sectionNameKeyPath: nil, cacheName: nil)
frc.delegate = self
return frc
}()
I want automatic updates on tableview..For that i have used NSFetchedResultsControlleras
lazy var fetchedResultsController: NSFetchedResultsController = {
// Initialize Fetch Request
let fetchRequest = NSFetchRequest(entityName: "Student")
// Add Sort Descriptors
let sortDescriptor = NSSortDescriptor(key: "grade", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Initialize Fetched Results Controller
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
// Configure Fetched Results Controller
fetchedResultsController.delegate = self
return fetchedResultsController
}()
But i have to filter the results after loading as of user selection as..
#IBAction func onSegmentValueChanged(sender: UISegmentedControl)
{
if sender.selectedSegmentIndex == 0{
//filter by grade
let fetchRequest = NSFetchRequest(entityName: "Student")
let sortDescriptor = NSSortDescriptor(key: "grade", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
let filterfetchResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
let predicate = NSPredicate(format: "address = %#","Russia")
filterfetchResultsController.fetchRequest.predicate = predicate
self.tableView.reloadData()
}else{
let fetchRequest = NSFetchRequest(entityName: "Student")
let sortDescriptor = NSSortDescriptor(key: "grade", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
let filterfetchResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
let predicate = NSPredicate(format: "grade = %d",10)
filterfetchResultsController.fetchRequest.predicate = predicate
self.tableView.reloadData()
}
}
This however reload the tableView but data is not filtered.how do i solve this problem?This is the demo project i am working on.Or should i use the normal way passing the results and reloading tableView as of normal way to solve this problem?
You must use self.fetchedResultsController, this is your datasource, not filterfetchResultsController: there´s no connection.
You must do a performFetch() to execute the changed predicates
This works for me:
#IBAction func onSegmentValueChanged(sender: UISegmentedControl)
{
if sender.selectedSegmentIndex == 1{
//filter by address
let predicate = NSPredicate(format: "address == %#","Russia")
self.fetchedResultsController.fetchRequest.predicate = predicate
}else{
let predicate = NSPredicate(format: "grade = %d",10)
self.fetchedResultsController.fetchRequest.predicate = predicate
}
do {
try self.fetchedResultsController.performFetch()
} catch {
let fetchError = error as NSError
print("\(fetchError), \(fetchError.userInfo)")
}
self.tableView.reloadData()
}
I've managed to create my UICollectionViewController with swift, and implement the NSFetchedResultsController and fetch stuff from my CoreData model. All good there... But...
I can't seem to call any of the NSFetchedResultsControllerDelegate methods from within my extension. Code is as follows:
extension MainsViewController: NSFetchedResultsControllerDelegate {
func fetchedResultsController() -> NSFetchedResultsController {
// if(fetchedResultsController != nil){
// return fetchedResultsController()
// }
var fetchRequest = NSFetchRequest()
var context: NSManagedObjectContext = RKObjectManager.sharedManager().managedObjectStore.mainQueueManagedObjectContext
var entity = NSEntityDescription.entityForName("Dessert", inManagedObjectContext: context)
fetchRequest.entity = entity
fetchRequest.fetchBatchSize = 20
var sortDescriptor = NSSortDescriptor(key: "createdAt", ascending: false)
let sortDescriptors = [sortDescriptor]
fetchRequest.sortDescriptors = sortDescriptors
fetchedResultsController().delegate = self
var aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: "Master")
var error: NSError?
if !aFetchedResultsController.performFetch(&error){
println("An error:\(error) occured.")
}
return aFetchedResultsController
}
//Here is where i would call *#optional func controllerWillChangeContent(_ controller: NSFetchedResultsController!)* etc. etc.
}
But swift doesnt recognise theese methods. I can't figure out what it is I am missing.
Would be great if someone could help me out.
Thanks in advance
Chris
I think it should something like this:
var fetchedResultsController: NSFetchedResultsController {
get {
var fetchRequest = NSFetchRequest()
var context: NSManagedObjectContext = RKObjectManager.sharedManager().managedObjectStore.mainQueueManagedObjectContext
var entity = NSEntityDescription.entityForName("Dessert", inManagedObjectContext: context)
fetchRequest.entity = entity
fetchRequest.fetchBatchSize = 20
var sortDescriptor = NSSortDescriptor(key: "createdAt", ascending: false)
let sortDescriptors = [sortDescriptor]
fetchRequest.sortDescriptors = sortDescriptors
self.fetchedResultsController.delegate = self
var aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: "Master")
var error: NSError?
if !aFetchedResultsController.performFetch(&error){
println("An error:\(error) occured.")
}
return aFetchedResultsController
}
}
So your MainsViewController is a class, as I said in the comment above, so the first line has to look like this:
class MainsViewController: UIViewController, NSFetchedResultsControllerDelegate {
Unfortunatly I cannot test the code, but this can be understood like this: You have a property called fetchedResultsController and this will execute, when the fetchedResultsController is getting. So in the getter like you would do it in objective-c with a lazy getting method.
I found out that it was simply the auto complete feature that wasn't suggesting the method to me. Typing it out manually 'fixed' the issue. Sorry for wasting everybody's time...
Chris