Detecting cell whose button was tapped

Question

On the FirstVC I have a variable index:

var index = -1

, which keeps the information of cell's indexPath.row so I can know in which cell the button was tapped. (Each cell has its own button)

I tried like this:
CellForRow:

cell.Btn.tag = indexPath.row cell.Btn.addTarget(self, action: #selector(detectButton), for: .touchUpInside)

and then:

@objc func detectButton(sender: UIButton) { self.index = sender.tag }

The secondVC is connected by the segue so I tried to send the index like this:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if segue.identifier == "MySegue" { let vc = segue.destination as! SecondVC vc.element = self.elements[index] } }

It crashes there because the index was still -1. I thought that @objc func detectButton will be called before prepareForSegue but it is not.
Why? And is there any other solution to send the index to the secondVC?

First time working with segues because I had to. Segue was defined in storyboard via button in cell. — stackich
– stackich, Commented Nov 12, 2020 at 13:24

vadian · Accepted Answer · 2020-11-12 14:40:08Z

You have to perform the segue *manually*:

Reconnect the segue from the view controller (rather than from the table view cell) to the destination controller

Delete var index = -1

Replace

@objc func detectButton(sender: UIButton) { self.index = sender.tag }

with (note the underscore after the open parentheses)

@objc func detectButton(_ sender: UIButton) { performSegue(withIdentifier: "MySegue", sender: sender.tag) }

Replace

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if segue.identifier == "MySegue" { let vc = segue.destination as! SecondVC vc.element = self.elements[index] } }

with

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if segue.identifier == "MySegue" { let vc = segue.destination as! SecondVC let index = sender as! Int vc.element = self.elements[index] } }

Edit:

Apparently in the current segue setup the button triggers the segue. If so delete var index = -1 and also the line cell.Btn.addTarget... (but not the line to assign the tag) and the entire method @objc func detectButton(_ sender: UIButton) { ... }.

In prepare(for segue get the tag from the sender parameter

override func prepare(for segue: UIStoryboardSegue, sender: Any?) { if segue.identifier == "MySegue" { let vc = segue.destination as! SecondVC let index = (sender as! UIButton).tag vc.element = self.elements[index] } }

let index = sender as! Int On that line I have a signal SIGABRT crash saying: Could not cast value of type 'UIButton' (0x1e64d07d8) to 'NSNumber' (0x1e648a658).
ok, changed but still having a crash saying Could not cast value of type '__NSCFNumber' (0x1e647e978) to 'UIButton' (0x1e64d07d8).
Walt a minute, you can't have both error messages. I meant to replace only let index = sender as! Int with let index = (sender as! UIButton).tag
Thanks, but I replaced already. I am not having bot error messages, the newest one I got is a little different from the first one.

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