Rami Ammoun Rami Ammoun - 1 month ago 13
iOS Question

swipe to delete UITableView cell animation is not working in swift 2

The swipe delete functionality is working fine, but i'm not able to add the animation, i tried everything i can but nothing worked. Whenever I add the code for animation, the app crashes when the cell is deleted. If you load the application again, you will find that the record was deleted, implying that the deletion was successful.

The crash error i'm getting is:


Invalid update: invalid number of rows in section 0. The number of
rows contained in an existing section after the update (1) must be
equal to the number of rows contained in that section before the
update (1), plus or minus the number of rows inserted or deleted from
that section (0 inserted, 1 deleted) and plus or minus the number of
rows moved into or out of that section (0 moved in, 0 moved out).


The animation code blocks i tried were:

//1
tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
//2
tableView.deleteRowsAtIndexPaths([indexPath],
withRowAnimation: UITableViewRowAnimation.Automatic)


I also tried to remove those codes and it didn't work too:

fetchAndSetResults()
treatmentProtocolsTableView.reloadData()

The entire code in the swift file is here, I commented out the animation blocks, and it works properly.

import UIKit
import CoreData

class Tx_Protocols: UIViewController, UITableViewDataSource, UITableViewDelegate {

//MARK: declaratoins.
weak var secureTextAlertAction: UIAlertAction?

//MARK: Core data related
var txProtocols = [TreatmentProtocolData]()
var selectedProtocol : TreatmentProtocolData? = nil

@IBOutlet weak var treatmentProtocolsTableView: UITableView!


//When button + is clicked, segue show add tx VC is initiated.
@IBAction func plusButtonAddTxProtocol(sender: AnyObject) {
self.performSegueWithIdentifier("showAddTxVC", sender: self)
}

override func viewDidLoad() {
super.viewDidLoad()

fetchAndSetResults()

treatmentProtocolsTableView.delegate = self
treatmentProtocolsTableView.dataSource = self
}

//When this is used, the data shows with a slight lag, slower.
override func viewDidAppear(animated: Bool) {
fetchAndSetResults()
treatmentProtocolsTableView.reloadData()
}

//This is how you catch the app delegate core data fnxnality, GRABBING THE PROPERTY IN APP DELEGATE
func fetchAndSetResults() {
let app = UIApplication.sharedApplication().delegate as! AppDelegate
let context = app.managedObjectContext
let fetchRequest = NSFetchRequest(entityName: "TreatmentProtocolData")

do {
let results = try context.executeFetchRequest(fetchRequest)
self.txProtocols = results as! [TreatmentProtocolData]
} catch let err as NSError {
print(err.debugDescription)
}
}



func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell: UITableViewCell = UITableViewCell(style: UITableViewCellStyle.Subtitle, reuseIdentifier:"Cell")
cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator
cell.textLabel!.adjustsFontSizeToFitWidth = true
cell.textLabel!.font = UIFont.boldSystemFontOfSize(17)

let treatmentProtocol = txProtocols[indexPath.row]
cell.textLabel!.text = treatmentProtocol.title
cell.imageView?.image = treatmentProtocol.getTxProtocolImage()

return cell
}

func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return txProtocols.count
}

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
tableView.deselectRowAtIndexPath(indexPath, animated: true)
self.selectedProtocol = txProtocols[indexPath.row]
self.performSegueWithIdentifier("showTxProtocol", sender: self)


}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

if segue.identifier == "showTxProtocol" {
let detailVC = segue.destinationViewController as! ShowTxProtocolDetailVC
detailVC.txProtocol = self.selectedProtocol
}
}


//MARK: Edittable table, delete button functionality.
func tableView(tableView: UITableView,
canEditRowAtIndexPath indexPath: NSIndexPath) -> Bool {
return true
}

func tableView(tableView: UITableView,
commitEditingStyle
editingStyle: UITableViewCellEditingStyle,
forRowAtIndexPath indexPath: NSIndexPath) {

if editingStyle == UITableViewCellEditingStyle.Delete {

let app = UIApplication.sharedApplication().delegate as! AppDelegate
let context = app.managedObjectContext
//1
let protocolToRemove =
txProtocols[indexPath.row]

//2
context.deleteObject(protocolToRemove)

//3
do {
try context.save()
} catch let error as NSError {
print("Could not save: \(error)")
}

// //1
// tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
// //2
// tableView.deleteRowsAtIndexPaths([indexPath],
// withRowAnimation: UITableViewRowAnimation.Automatic)

fetchAndSetResults()
treatmentProtocolsTableView.reloadData()

}
}


}


I appreciate your help

Answer

You need to encapsulate inside beginUpdates() and endUpdates(). Also, update your data model that is used to load the table view:

self.tableView.beginUpdates()
self.txProtocols.removeObjectAtIndex(indexPath.row) // Check this out 
self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
self.tableView.endUpdates()
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