So my numberOfRowsInSection is:
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard let delegate = delegate else { return 0 }
return delegate?.comments.count + 1
}
I added one more to compensate for the "load more" which is on top of the table view (in this case, it's row 0).
Here's the thing: when I want to remove that cell "load more" after fetching the max amount of posts, it gives me an error:
The number of rows contained in an existing section after the update (12) must be equal to the number of rows contained in that section before the update (11), 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).'
So here's the function that causes the error:
func loadMore() {
// loadMoreComments(completion:) inserts the new comment objects inside
// the data source in the beginning of the list.
delegate?.loadMoreComments(completion: { (isEndOfPosts, newCommentCount, comments) in
self.didReachEndOfPosts = isEndOfPosts
if isEndOfPosts {
// indexPaths just returns [[0,1]], or, just one row.
let indexPaths = self.createIndexPathsForNoMorePosts(newCommentCount: newCommentCount)
self.tableView.beginUpdates()
// error happens here.
self.tableView.deleteRows(at: [IndexPath(row: 0, section: 0)], with: .automatic)
self.tableView.endUpdates()
// assume only one post comes in, and that's the last one.
self.tableView.beginUpdates()
self.tableView.insertRows(at: indexPaths, with: .automatic)
self.tableView.endUpdates()
}
}
What I'm trying to accomplish is this: once i get the last post, remove the "load more" cell, and insert the last few posts, replacing the 0 row with the first of the last few posts.
You need to notify your tableView's datasource about cell count change. Create a class variable, something like
var shouldShowLoadMoreCell = true
and than modify numberOfRowsInSection method
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard let delegate = delegate else { return 0 }
if shouldShowLoadMoreCell {
return delegate?.comments.count + 1
} else {
return delegate?.comments.count
}
}
finally, set this flag when needed
self.tableView.beginUpdates()
shouldShowLoadMoreCell = false
self.tableView.deleteRows(at: [IndexPath(row: 0, section: 0)], with: .automatic)
self.tableView.endUpdates()
Related
I have a tableview with two sections.
var categories = ["a", "b", "c"]
var items = ["1" , "2", "3"]//will be different based on category selection
var selectedCategory: String?
Initially first section only visible. After the user selects any row in 0th section section 1 will have 3 rows and section 0 will have only selected row.
For ex. if category "b" is selected "a","c" rows should be removed and "1","2","3" rows should be added.
Now if the "b" is deselected "a","c" rows should be added and "1","2","3" rows should be removed.
//UITableViewDataSource
func numberOfSections(in tableView: UITableView) -> Int {
return selectedCategory == nil ? 1 : 2
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return section == 0 ? categories.count : items.count
}
I've done this using tableView.reloadData(). It does't show any animation. I'm trying to achieve this using the following methods
tableView.deleteRows(at: [IndexPath], with: UITableViewRowAnimation)
tableView.insertRows(at: [IndexPath], with: UITableViewRowAnimation)
I'm struggling to get indexpaths to insert and delete
instead of reload whole tableView do this:-
tableView.beginUpdates()
tableView.deleteRows(at: [IndexPath], with: UITableViewRowAnimation.top)
tableView.insertRows(at: [IndexPath], with: UITableViewRowAnimation.top)
tableView.endUpdates()
You need to wrap the deleteRows and insertRows call in tableView.beginUpdates and tableView.endUpdates.
https://developer.apple.com/documentation/uikit/uitableview/1614908-beginupdates?language=objc
Or use performBatchUpdates:completion:.
https://developer.apple.com/documentation/uikit/uitableview/2887515-performbatchupdates?language=objc
Edit
Ok, let me explain some things in detail. :-)
First I think you need to modify numberOfRowsInSection, because you said section 0 should show all categories as long as none is selected and after selecting one, it should display only that one row.
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
switch section {
case 0:
// If no category is selected, we display all categories, otherwise only the selected one.
return selectedCategory == nil ? categories.count : 1
case 1:
return items.count
default:
return 0
}
}
Second, this is an example of how didSelectRowAt could look like. I changed selectedCategory to Int? to store the index of the selected category and not its name.
As you can see, in section 0 the rows that are not the selected category are deleted, while section 1 is added completely, as it did not exist before.
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if selectedCategory == nil {
// Save index on selected category
selectedCategory = indexPath.row
// set items array
…
// Animate change
var indexPaths = [IndexPath]()
for (index, _) in categories.enumerated() {
if index != selectedCategory {
indexPaths.append(IndexPath(row: index, section: 0))
}
}
tableView.performBatchUpdates({
// delete rows from section 0
tableView.deleteRows(at: indexPaths, with: .automatic)
// insert section 1
tableView.insertSections(IndexSet(integer: 1), with: .automatic)
}, completion: nil)
}
}
I have an array I need to add and remove cell data on click of "close" which is UIButton in header section
I am looping the array and getting row and for section I have used static data and appending in indexPaths then after
tblSideNav.deleteRows(at: indexPaths, with: .fade)
as above line start executing app got crash
var menusArray = [sideNavStruct(isOpend: true, menuImg: "user", menuTitle: "Profile", subMenu: ["My Profile", "Distributor Profile"]), sideNavStruct(isOpend: true, menuImg: "user", menuTitle: "Reports", subMenu: ["Stock Report", "NFR Report", "RTD”])]
#objc func handleOpenCloseCell() {
let section = 0
var indexPaths = [IndexPath]()
for row in menusArray[section].subMenu.indices {
let indexPath = IndexPath(row: row, section: section)
indexPaths.append(indexPath)
}
print(indexPaths.count)
print(menusArray[section].subMenu[0])
menusArray[section].subMenu[0].removeAll()
tblSideNav.deleteRows(at: indexPaths, with: .fade)
}
my app got crash on tblSideNav.deleteRows(at: indexPaths, with: .fade):
Invalid update: invalid number of rows in section 0. The number of
rows contained in an existing section after the update (7) must be
equal to the number of rows contained in that section before the
update (2), plus or minus the number of rows inserted or deleted from
that section (0 inserted, 2 deleted) and plus or minus the number of
rows moved into or out of that section (0 moved in, 0 moved out).
I am not able to find the issue
First of all, you are calling deleteRows without beginUpdates and endUpdates which is required.
tableView.beginUpdates()
tableView.deleteRows(at: indexPaths, with: .fade)
tableView.endUpdates()
The same error can occur if your delegate function is not returning the correct number of rows after the update.
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return rowCount
}
I believe that better practice would be to change/empty the variable where you're storing your rows information/data and simply call reloadData().
I have a question about making a table view section expand/collapse. There are many pieces of information on the web about this topic, but my question is a little bit different.
My question is, how can I make an additional section when the user taps on another section?
The following images may help you understand my situation.
At the top of the table view we have one small section (section 0).
If I tap it...
Section 1 and 2 should be created between section 0 and 3.
How can I do this? Is there any way or code? Please help me.
Also, I tried this code but got a sigabrt error :(
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
self.tableView.beginUpdates()
let indexSet = NSMutableIndexSet()
indexSet.add(indexPath.section + 1)
indexSet.add(indexPath.section + 2)
if indexPath.section == 0 {
if expandCol == true {
self.tableView.deleteSections(NSIndexSet(index: 1) as IndexSet, with: .automatic)
self.tableView.deleteSections(NSIndexSet(index: 2) as IndexSet, with: .automatic)
expandCol = !expandCol
} else {
self.tableView.insertSections(NSIndexSet(index: 1) as IndexSet, with: .automatic)
self.tableView.insertSections(NSIndexSet(index: 2) as IndexSet, with: .automatic)
expandCol = !expandCol
}
}
self.tableView.endUpdates()
self.tableView.reloadData()
}
You can keep a flag variable on view-controller for selectedSection.
var selectedSection: Int = -1
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return section == selectedSection ? <section-row-count> : 0
}
Set the flag value in section header action method:
func actionSectionHeader(tag: Int) {
selectedSection = tag
self.tableView.reloadData()
}
To add a new section into UITableView, you need
1 - Update your data. For example, insert your sections in a data array, or change their visibility flags.
2 - Call the following method.
tableView.insertSections([1, 2], with: .automatic)
or
tableView.reloadData()
The first method will update your UITableView with an animation. The second one will update it instantly. For better UX I'd recommend you to use the first one.
Update on your code
At first, you can pass all sections indices at once using a simple array. Like that
if expandCol {
self.tableView.deleteSections([1, 2], with: .automatic)
} else {
self.tableView.insertSections([1, 2], with: .automatic)
}
expandCol = !expandCol
The second problem is that you're calling reloadData after you call the animated update of your table.
And the most important, you need to change the data. You UITableView has a dataSource and it returns a number of sections and cells. After user interacts with your trigger cell, you need to make changes at that data before calling the update.
I am building an iOS app, basically the user create an item by pressing the "+" button and then the app should put the new item in according section of the table based on the location of the item. However I got the error: Invalid update: invalid number of rows in section 1. 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. Here is my code, thank you
let sections = ["Bathroom", "Bedroom", "Dining Room", "Garage", "Kitchen", "Living Room"]
#IBAction func addNewItem(_ sender: UIBarButtonItem) {
/*
//Make a new index path for the 0th section, last row
let lastRow = tableView.numberOfRows(inSection: 0)
let indexPath = IndexPath(row: lastRow, section: 0)
//insert this new row into the table
tableView.insertRows(at: [indexPath], with: .automatic)*/
//Create a new item and add it to the store
let newItem = itemStore.createItem()
var Num: Int = 0
if let index = itemStore.allItems.index(of: newItem) {
switch newItem.room {
case "Bathroom":
Num = 0
print("I am in here")
case "Bedroom":
Num = 1
case "Dining Room":
Num = 2
case "Garage":
Num = 3
case "Kitchen":
Num = 4
case "Living Room":
Num = 5
default:
Num = 0
print("I am in Default")
}
let indexPath = IndexPath(row: index, section: Num)
tableView.insertRows(at: [indexPath], with: .automatic)
}
override func numberOfSections(in tableView: UITableView) -> Int {
return sections.count
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return itemStore.allItems.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//create an instance of UITableViewCell, with default appearance
//let cell = UITableViewCell(style: .value, reuseIdentifier: "UITableViewCell")
//get a new or recycled cell
//if indexPath.row < itemStore.allItems.count {
let cell = tableView.dequeueReusableCell(withIdentifier: "ItemCell", for: indexPath) as! ItemCell
//Set the text on the cell with the decription of the item
//that is at the nth index of items, where n = row this cell
//will appear in on the table view
let item = itemStore.allItems[indexPath.row]
if item.name == "" {
cell.nameLabel.text = "Name"
} else {
cell.nameLabel.text = item.name
}
if item.serialNumber == nil {
cell.serialNumberLabel.text = "Serial Number"
} else {
cell.serialNumberLabel.text = item.serialNumber
}
cell.valueLabel.text = "$\(item.valueInDollars)"
cell.roomLabel.text = item.room
if item.valueInDollars < 50 {
cell.valueLabel.textColor = UIColor.green
}else if item.valueInDollars >= 50 {
cell.valueLabel.textColor = UIColor.red
}
cell.backgroundColor = UIColor.clear
return cell
}
override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
let LocationName = sections[section]
return LocationName
}
thank you so much for your time!
and this is how I create item
#discardableResult func createItem() -> Item {
let newItem = Item(random: false)
allItems.append(newItem)
return newItem
}
The problem is that you should insert the item in the array first:
itemStore.allItems.append(newItem)
Also, there is a difference between sections and rows in numberOfRowsInSection(return number of rows for every section) you have a switch that returns the same number, it should be
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return itemStore.allItems.count
}
Edit :
The problem is when the table loads there is 0 rows for all the sections ( itemStore.allItems.count is zero ), when you try to insert a row say at section 0 , row 0 -- the dataSource must be updated only for that section , which is not happen in your case as it's the same array that is returned for all sections , so you must either have an array of array where inner array represent number of rows so addition/deletion from it doesn't affect other ones ,,,,, or lock the insert to say section 0 like this
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if (section == 0 ) {
return itemStore.allItems.count
}
return 0
}
in this edit i inserted in 2 sections 0 and 2 with no crash because i handled numberOfRowsInSection to return old numbers for old section that why to be able to insert in all sections you must have a different data source array or manage from numberOfRowsInSection , see edited demo here Homepwner
Instead of setting footer in viewDidLoad implement this method
override func tableView(_ tableView: UITableView, viewForFooterInSection section: Int) -> UIView? {
if(section == 5 ) {
let textLabel = UILabel()
textLabel.text = "No more Item"
return textLabel
}
return nil
}
There is something terribly wrong with your data source. Your numberOfRow for all sections is the same. i.e. itemStore.allItems.count. Which means you are setting the same number of rows in each section.
The main issue is, while adding a new item, you are inserting a new row in the specific section which means
new number of rows for section = previous number of rows in section +
1
However, there is no addition in the data source.
So according to the code, you have inserted a new row, but your data source has one record less since you didn't add the item there.
So I would like you do the following in order of these steps :
Add item in required data source.
inserRowInSection
Update : Remove the condition in cellForRowAtIndexPath :
if indexPath.section <= 1 and it's else block. You don't need that. If number of sections is less than 1, it won't be called. Moreover it's the else block which is getting called all the time because you already have sections in your code. So if case will never be called.
So I got the issue. In itemStore.createItem() the value for room is always Room. In the switch-case, you never have Room case. So it always falls in default case. You need to fix that.
#Jacky.S I downloads your code and try to debug it.Fist look our error properly.
reason: 'Invalid update: invalid number of rows in section 1. 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 (0)
So It says before update, your sections has 0 rows. Now you try to update you tableview using this piece of code.
print(indexPath)
tableView.insertRows(at: [indexPath], with: .automatic)
I just added the print statement for debugging purpose and it prints [0, 0] .So you say your tableview to insert 0th row on section 0.
Now when you insert any row into tableview it calls the delegate method.Now look at the below delegate method.
override func tableView(_ tableView: UITableView, numberOfRowsInSection
section: Int) -> Int {
if section == 0{
print("0",itemStore.allItems.count)
}
if section == 1{
print("1",itemStore.allItems.count)
}
// print(itemStore.allItems)
return itemStore.allItems.count
}
In your code you just return itemStore.allItems.count.I added the above code for debugging.Now look that itemStore.allItems.count always return 1.So for first section it works perfectly because few times ago you insert a row in first section whose index is [0 = row, 0 = section].So you previously returned rows for section 0 is equal to the recently return rows for section 0.But When it comes for section 1 you previously return no row that means your section 1 has no rows in previous but in your above delegate method you also return 1 row for section 1.Which is conflicting because in previous you never update or return any rows for section 1.That's why you code crash and and say that
your number of rows contained in an existing section after the update is 1 which must be equal to the number of rows contained in that section before the update. Which is 0.
So this is the explanation for you crash.
Now, to recover from crash your allItems should be a dictionary or an array of array.
var allItems = [[Item]]()
or
var allItems = ["String":[Item]]()
guess allItems element is something like this
allItems = ["bathroom":[item1, item2, item3],"bedroom":[item1, item2, item3, item4]]
so here you have 2 section one is bathroom and another is bedroom.First section have 3 row and second one have 4 row and in you tableview delegate method you have to return 3 for section 0 and 4 for section 1
Hi friends of StackOverflow.
I have a chat screen on my app and I it perform a insertion and deletion based on the actual size of the an Array. Look this:
func addObject(object: Object?) {
if comments == nil || object == nil || object?.something == nil || object?.anything == nil {
return
}
self.objectsTableView.beginUpdates()
if self.objects!.count == 10 {
self.objects?.removeAtIndex(9)
self.objectsTableView.deleteRowsAtIndexPaths([NSIndexPath(forRow : 9, inSection: 0)], withRowAnimation: .Right)
}
self.objects?.insert(object!, atIndex: 0)
self.objectsTableView.insertRowsAtIndexPaths([NSIndexPath(forRow : 0, inSection: 0)], withRowAnimation: .Right)
self.objectsTableView.endUpdates()
}
But after some stress test, the log notify:
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 (10), 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 don't know whats happening, this happens only when the insert of objects is very extreme, like one per 0.2 seconds.
Someone know that I can do?
Model mismatch
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 (10), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted)
In plain English for the reasonable man, the UITableView thinks you should have 11 rows:
10 before the update + 1 inserted.
number of rows contained in an existing section after the update (1)
...refers to numberOfRowsInSection is returning 1 for section 0, which indicates that the objects array is out of sync, assuming you use something like below:
override func tableView(tableView: UITableView,
numberOfRowsInSection section: Int) -> Int {
return objects.count
}
Use NSFetchedResultsController
A clean solution is to use NSFetchedResultsController to be the interface between your model and the UI. It has well studied boilerplate code and is a great platform to ensure thread safety. Documentation here.
Note:
Neat effect! The cell seems to rotate around to the top.
I could not break it using the Gist you produced, nor scheduling multiple concurrent tests. There must be a rogue access to your Object array.
Demo
This simplified version works. Just hook doPlusAction to a button action and watch it loop:
class TableViewController: UITableViewController {
var objects:[Int] = [0,1,2,3,4]
var insertions = 5
#IBAction func doPlusAction(sender: AnyObject) {
tableView.beginUpdates()
objects.removeAtIndex(4)
tableView.deleteRowsAtIndexPaths([NSIndexPath(forRow: 4, inSection: 0)], withRowAnimation: .Right)
objects.insert(insertions++, atIndex: 0)
tableView.insertRowsAtIndexPaths([NSIndexPath(forRow: 0, inSection: 0)], withRowAnimation: .Right)
tableView.endUpdates()
let delay = 0.1 * Double(NSEC_PER_SEC) //happens the same with this too, when reach 100-150 items
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue()) { () -> Void in
self.doPlusAction(self)
}
}
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return objects.count
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("reuseIdentifier", forIndexPath: indexPath)
cell.textLabel!.text = "Cell \(objects[indexPath.row])"
return cell
}
}
Name of the guy that solved the problem: Semaphore
The error still happens, but only with a high size of items on list. I don't know what can be.
The DataSource protocol:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
let count = self.objects?.count ?? 0
if self.semaphore != nil && semaphoreCode == BLOCKED_STATE {
dispatch_semaphore_signal(self.semaphore!)
}
return count
}
The method that add object:
func addObject(object: Object?) {
if object == nil {
return
}
if self.semaphore != nil {
let tempSemaCode = dispatch_semaphore_wait(semaphore!, 100000)
if tempSemaCode == BLOCKED_STATE {
self.semaphoreCode = RELEASED_STATE
}
}
if self.objects != nil && semaphoreCode != BLOCKED_STATE {
var needsRemoveLastItem = false
if self.objects!.count == 10 {
self.objects?.removeAtIndex(9)
needsRemoveLastItem = true
}
self.objects?.insert(object!, atIndex: 0)
if self.objects!.count > 0 {
self.objectsTableView.beginUpdates()
if needsRemoveLastItem {
self.objectsTableView.deleteRowsAtIndexPaths([NSIndexPath(forRow : 9, inSection: 0)], withRowAnimation: .Right)
}
self.objectsTableView.insertRowsAtIndexPaths([NSIndexPath(forRow : 0, inSection: 0)], withRowAnimation: .Right)
self.objectsTableView.endUpdates()
self.semaphore = dispatch_semaphore_create(BLOCKED_STATE)
}
}
}