UITableView cell insertion failure - ios

Question

I am trying to make a UITableView that can have expandable header views. When you press a button inside of the header view, the following function gets executed:
func expandTheCell(_ sender: UIButton) {
self.tableView.beginUpdates()
if sender.isExpanded == false {
postsArray.append("Hello")
tableView.reloadData()
print("Array Count: \(postsArray.count)")
self.tableView.insertRows(at: [IndexPath.init(row: 0, section: sender.tag)], with: .fade)
} else {
print("test")
}
self.tableView.endUpdates()
}
This are some table view functions:
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return postsArray.count
}
func numberOfSections(in tableView: UITableView) -> Int {
return 3
}
When I try to insert the rows, I get the following error:
Terminating app due to uncaught exception
'NSInternalInconsistencyException', reason: 'Invalid update: invalid
number of rows in section 1
How come I can't insert the cells? What am I doing wrong?

Answer 1

I think problem is due to having same dataSource array for the sections, in your case postsArray , when you append the item to postsArray on clicking the button , same postsArray is used for other sections, so after you insert the row in section 0 , section 1 complains that number of rows for me before and after insert operation is not same, but section 0 doesnt complain because it has same number of rows and number of items in postsArray
Now this problem can be solved in two ways:
First way is that you can insert the row for other sections as well, then all the sections have equal number of rows as the number of elements in postsArray
Second way is that you have different dataSource arrays for all the sections , like postsArray1 for section 1, postsArray2 for section 2 and same for other sections. Now in this case you dont need to insert rows for other sections , since each section has different dataSource array, changing one wont affect others.
I have made a simple project to demonstrate the above theory:
class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
#IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(buttonTapped(_:)))
self.navigationItem.rightBarButtonItem = addButton
}
var valuesFirstSection = ["value1", "value2", "value3"]
var valuesSecondSection = ["value1Second", "value2Second", "value3Second"]
//if you want to have the same dataSource array then use this
//var sharedValues = ["value1Shared", "value2Shared", "value3Shared"] // shared dataSource array
func numberOfSections(in tableView: UITableView) -> Int {
return 2
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if section == 0 {
return valuesFirstSection.count
}else {
return valuesSecondSection.count
}
// //if you want to have the same dataSource array then
//use this
//return sharedValues.count;
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
if indexPath.section == 0 {
cell.textLabel?.text = valuesFirstSection[indexPath.row]
}else {
cell.textLabel?.text = valuesSecondSection[indexPath.row]
}
return cell
//if you want to have the same dataSource array then
//use this
//cell.textLabel?.text = sharedValues[indexPath.row]
//return cell
}
func buttonTapped(_ sender: UIBarButtonItem) {
//if you want to have the same dataSource array then
//you need to insert the rows for other sections as well
// sharedValues.insert("NewValue0", at: 0)
// self.tableView.insertRows(
// at: [IndexPath(row: 0, section: 0),
// IndexPath(row: 0, section: 1)
// ],
// with: .automatic)
valuesFirstSection.insert("NewValue0", at: 0)
self.tableView.insertRows(
at: [IndexPath(row: 0, section: 0)
],
with: .automatic)
}
}
Hope this helps.