I have 100 cells. In each cell I have 5 button. How can I check which cell button is clicked?

Ans : 

There are various approach for this problem. But following two approach are better.

Approach-1 : Delegate - Protocol 

Cell : 

protocol CellSubclassDelegate: class {

    func buttonTapped(cell: CellSubclass)

}

class CellSubclass: UITableViewCell {

@IBOutlet var someButton: UIButton!

weak var delegate: CellSubclassDelegate?

override func prepareForReuse() {

    super.prepareForReuse()

    self.delegate = nil

}

@IBAction func someButtonTapped(sender: UIButton) {

    self.delegate?.buttonTapped(self)

}

ViewController:

class MyViewController: UIViewController, CellSubclassDelegate {

    @IBOutlet var tableview: UITableView!

    func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as! CellSubclass

        cell.delegate = self

    }

    func buttonTapped(cell: CellSubclass) {

        guard let indexPath = self.tableView.indexPathForCell(cell) else {

            // Note, this shouldn't happen - how did the user tap on a button that wasn't on screen?

            return

        }

        //  Do whatever you need to do with the indexPath

        print("Button tapped on row \(indexPath.row)")

    }

} 

Approach-2 Using Closure:

Cell :

class MyCell: UITableViewCell {

    var button: UIButton!

    var buttonAction: ((Any) -> Void)?

    @objc func buttonPressed(sender: Any) {

        self.buttonAction?(sender)

    }

}

ViewController : 

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as! MyCell

    cell.buttonAction = { sender in

        // Do whatever you want from your button here.

    }

    // OR

    cell.buttonAction = buttonPressed(closure: buttonAction, indexPath: indexPath) // <- Method on the view controller to handle button presses.

}

No need to explain code. Simple as that.

If you have any comment, question, or recommendation, feel free to post them in the comment section below!