Invalid Update When adding Rows to UITableView - ios

Question

Invalid update: invalid number of rows in section 0. The number of
rows contained in an existing section after the update (5) 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 (1 inserted, 0 deleted) and plus or minus the number of
rows moved into or out of that section (0 moved in, 0 moved out).
I'm trying to add rows to a table view when a user taps a row, to create an expandable section, however the extra rows aren't being counted before Xcode tries to add them in and as such causes this error (I think). Can anybody point me in the right direction?
// sectionExpanded is set to false in viewDidLoad. It is set to true when
// the user taps on the expandable section (section 0 in this case)
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if section == 0 && sectionExpanded {
return 5
} else {
return 1
}
}
// This should recount the rows, add the new ones to a temporary array and then add
// them to the table causing the section to 'expand'.
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let selectedItem = menu[indexPath.row]
let cell = tableView.cellForRowAtIndexPath(indexPath) as MenuCell
if indexPath.section == 0 {
var rows: Int
var tmpArray: NSMutableArray = NSMutableArray()
sectionExpanded = !sectionExpanded
rows = tableView.numberOfRowsInSection(0)
for i in 1...rows {
var tmpIndexPath: NSIndexPath
tmpIndexPath = NSIndexPath(forRow: i, inSection: 0)
tmpArray.addObject(tmpIndexPath)
}
if !sectionExpanded {
tableView.deleteRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
} else {
tableView.insertRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
}
} else {
delegate?.rightItemSelected(selectedItem)
}
}

Answer 1

It is telling you that you are trying to insert 1 new row, but numberofrows should be 5, before was 1 and you are trying to insert 1 new row, thats 2. Theres your problem.
rows = tableView.numberOfRowsInSection(0) //this returns 1
for i in 1...rows { //
var tmpIndexPath: NSIndexPath
tmpIndexPath = NSIndexPath(forRow: i, inSection: 0)
tmpArray.addObject(tmpIndexPath)//this will contain only 1 object, because the loop will run only for 1 cycle
}
EDIT
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let selectedItem = menu[indexPath.row]
let cell = tableView.cellForRowAtIndexPath(indexPath) as MenuCell
if indexPath.section == 0 {
var rows: Int
var tmpArray: NSMutableArray = NSMutableArray()
sectionExpanded = !sectionExpanded
rows = 1
if sectionExpanded {
rows = 5
}
for i in 1...rows {
var tmpIndexPath: NSIndexPath
tmpIndexPath = NSIndexPath(forRow: i, inSection: 0)
tmpArray.addObject(tmpIndexPath)
}
if !sectionExpanded {
tableView.deleteRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
} else {
tableView.insertRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
}
} else {
delegate?.rightItemSelected(selectedItem)
}
}
Since you know number of rows will be always 5 or 1, you can try something like this. However, this is not a standard approach, I would suggest to alter your datasource array.
Here is some example how to do it: http://www.nsprogrammer.com/2013/07/updating-uitableview-with-dynamic-data.html its for Objective-C but you will get the gist of it.

Answer 2

You can try modifying the data source and then reload the table.

Answer 3

You should use insertRowsAtIndexPaths... and the like between a beginUpdates() and endUpdates(). The tableView will collect all the changes after beginUpdates() and then will apply them coherently after endUpdates(). So try something like:
tableView.beginUpdates()
if !sectionExpanded {
tableView.deleteRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
} else {
tableView.insertRowsAtIndexPaths(tmpArray, withRowAnimation: UITableViewRowAnimation.Top)
}
tableView.endUpdates()
Remember that after the call to endUpdates() the number of sections and rows must be consistent with your model.
Since I don't know about your model, here's a simple example:
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
#IBOutlet weak var tableView: UITableView!
var sectionExpanded: Bool = false {
didSet {
if oldValue != sectionExpanded {
let expIndexes = map(0..<model.count) { r in
NSIndexPath(forRow: r, inSection: 0)
}
// Here we start the updates
tableView.beginUpdates()
switch sectionExpanded {
case false:
// Collapsing
tableView.deleteRowsAtIndexPaths(expIndexes, withRowAnimation: .Top)
tableView.insertRowsAtIndexPaths([NSIndexPath(forRow: 0, inSection: 0)], withRowAnimation: .Top)
default:
// Expanding
tableView.deleteRowsAtIndexPaths([NSIndexPath(forRow: 0, inSection: 0)], withRowAnimation: .Top)
tableView.insertRowsAtIndexPaths(expIndexes, withRowAnimation: .Bottom)
}
// Updates ended
tableView.endUpdates()
}
}
}
let model = ["foo", "bar", "zoo"]
//MARK: UITableView DataSource
struct TableConstants {
static let sectionCellIdentifier = "SectionCell"
static let expandedCellIdentifier = "ExpandedCell"
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return 1
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return sectionExpanded ? model.count : 1
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
switch sectionExpanded {
case false:
let cell = tableView.dequeueReusableCellWithIdentifier(
TableConstants.sectionCellIdentifier,
forIndexPath: indexPath) as UITableViewCell
cell.textLabel?.text = "The Section Collapsed Cell"
return cell
default:
let cell = tableView.dequeueReusableCellWithIdentifier(
TableConstants.expandedCellIdentifier,
forIndexPath: indexPath) as UITableViewCell
cell.textLabel?.text = "\(model[indexPath.row])"
cell.detailTextLabel?.text = "Index: \(indexPath.row)"
return cell
}
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
sectionExpanded = !sectionExpanded
}
}
Note that I moved the table updates to the sectionExpanded observer.

Answer 4

You already have 1 row in section = 0, and trying to insert 5 new rows. You can only add 4 rows more to map with numberOfRowsInsection.
Try following code:
sectionExpanded = !sectionExpanded
rows = self.numberOfRowsInSection(0)-1
for i in 1...rows {
var tmpIndexPath: NSIndexPath
tmpIndexPath = NSIndexPath(forRow: i, inSection: 0)
tmpArray.addObject(tmpIndexPath)
}