tableview issue, indexPath is nil

Question

I have a button and a label in a table view (I am using 8 rows )and for some reason when I click the first button I get indexPath nil error, but when I click the second button (2nd row) I get the first row label. When I click the 3rd row button, I get the second row label etc. Why are they misaligned. I want when I click the first row button to get the first row label etc. Please see the code below. Thank you !!

   @objc func btnAction(_ sender: AnyObject) {


    var position: CGPoint = sender.convert(.zero, to: self.table)

    print (position)
    let indexPath = self.table.indexPathForRow(at: position)
    print (indexPath?.row)
    let cell: UITableViewCell = table.cellForRow(at: indexPath!)! as
    UITableViewCell


      print (indexPath?.row)
    print (currentAnimalArray[(indexPath?.row)!].name)
    GlobalVariable.addedExercises.append(currentAnimalArray[(indexPath?.row)!].name)

}


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    guard let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as? TableCell else {return UITableViewCell() }

   // print(indexPath)

    cell.nameLbl.text=currentAnimalArray[indexPath.row].name
 // print("\(#function) --- section = \(indexPath.section), row = \(indexPath.row)")

   // print (currentAnimalArray[indexPath.row].name)

    cell.b.tag = indexPath.row

   // print (indexPath.row)
    cell.b.addTarget(self, action: #selector(SecondVC.btnAction(_:)), for: .touchUpInside)


    return cell



}

Frame math is rather the worst way to get the index path. Why don't you use the tag you assigned to the button? I recommend to move the button action into the (custom) cell and use a callback closure which is the most efficient solution. — vadian, Aug 27 '18 at 05:33
@vadian thanks, do you have an example on how I can do that? — Bubu, Aug 27 '18 at 05:40
@Bubu **Try this One** https://stackoverflow.com/q/28659845/10150796 — Nikunj Kumbhani, Aug 27 '18 at 05:43
@NikunjKumbhani thanks that link you gave fixed my issue of position — Bubu, Aug 27 '18 at 05:52

vadian · Accepted Answer · 2018-08-27T06:02:30.907

Frame math is a worst-case scenario if you have no choice. Here you have a lot of choices.

For example why don't you use the tag you assigned to the button?

@objc func btnAction(_ sender: UIButton) {
    GlobalVariable.addedExercises.append(currentAnimalArray[sender.tag].name)
}

A swiftier and more efficient solution is a callback closure:

In TableCell add the button action and a callback property. The outlet is not needed. Disconnect the outlet and connect the button to the action in Interface Builder. When the button is tapped the callback is called.

class TableCell: UITableViewCell {

    // @IBOutlet var b : UIButton!
    @IBOutlet var nameLbl : UILabel!

    var callback : (()->())?

    @IBAction func btnAction(_ sender: UIButton) {
        callback?()
    }
}

Remove the button action in the controller.

In cellForRow assign a closure to the callback property

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    // no guard, the code must not crash. If it does you made a design mistake
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! TableCell

    let animal = currentAnimalArray[indexPath.row]
    cell.nameLbl.text = animal.name

    cell.callback = {
         GlobalVariable.addedExercises.append(animal.name)
    }

    return cell
}

You see the index path is actually not needed at all. The animal object is captured in the closure.

Faysal Ahmed · Answer 2 · 2018-08-28T04:22:39.397

0

You already pass indexPath.row with button tag. Use the tag as index simply

@objc func btnAction(_ sender: UIButton) { 
    GlobalVariable.addedExercises.append(currentAnimalArray[sender.tag].name)
}

edited Aug 28 '18 at 04:22

answered Aug 27 '18 at 05:52

Faysal Ahmed

7,501
5
28
50

This does not compile – vadian Aug 27 '18 at 05:52
Yes, but it's much easier to change the type of the `sender` in the signature – vadian Aug 27 '18 at 05:56
Yes got it. Changed. – Faysal Ahmed Aug 27 '18 at 05:57

tableview issue, indexPath is nil

2 Answers2