How to Change previous button color when pressed the next button?

Question

I have a number of buttons in a horizontal UIScrollView added programmatically. I have to change the color of the user selected button. But if user select another button the previous button color must be change to default color. how can I do this? Please help me...

func createHorizontalScroll()
{
    let scrollView = UIScrollView(frame: CGRect(x: CGFloat(0), y: CGFloat(410), width: CGFloat(view.frame.size.width), height: CGFloat(40)))

    var buttonX: CGFloat = 0

    for index in 0..<btnNames.count
    {
        //add an element and the previous element together
        let sum = btnNames[index]

        button = UIButton(frame: CGRect(x: CGFloat(buttonX), y: CGFloat(0), width: CGFloat(100), height: CGFloat(40)))

        print("btnNames:\(sum)")

        button.setTitle("\(sum)",for:.normal)
        button.layer.borderWidth = 2.5
        button.layer.borderWidth = 2.5
        button.layer.borderColor = UIColor.white.cgColor
        button.layer.backgroundColor = UIColor.black.cgColor
        button.tag = index
        scrollView.addSubview(button)
        buttonX = button.frame.size.width + buttonX

        button.addTarget(self, action: #selector(changeView), for: .touchUpInside)
    }

    scrollView.contentSize = CGSize(width: CGFloat(buttonX), height: CGFloat(scrollView.frame.size.height))
    scrollView.backgroundColor = UIColor.clear
    view.addSubview(scrollView)
}

func changeView(_ sender: UIButton)
{
   print("I Clicked a button \(Int(sender.tag))")
}

Answer 1

Since you're already using tags it shouldn't be a problem. The changeView function should work like this:

func changeView(_ sender: UIButton)
{
    let scrollView = sender.superview as! UIScrollView //This is mildly hacky - store your scroll view in an instance variable
    for view in scrollView.subviews {
        guard let button = view as? UIButton else {
            continue
        }

        button.backgroundColor = sender.tag == button.tag ? UIColor.red : UIColor.black
    }
}

Answer 2

Simple solution without tags.

Declare a property currentButton

weak var currentButton : UIButton?

In changeView reset the color of the currentButton , set the color of the sender and assign the sender to currentButton .

func changeView(_ sender: UIButton)
{
    currentButton?.backgroundColor = .black
    currentButton = sender
    sender.backgroundColor = .red
}

Due to optional chaining the color of currentButton will not be set if currentButton is nil.

Answer 3

Keep a week property of type UIButton to temporally save the selected button.

weak var selectedButton: UIButton?

In the selector for your buttons make the color of the selectedButton to default, then change the color of the newly selected button and reset the selectedButton

@IBAction func actionTouchUpInside(sender: UIButton) {
    if let selectedButton = self.selectedButton {
        selectedButton.backgroundColor = UIColor.clear
    }

    sender.backgroundColor = UIColor.blue
    selectedButton = sender
}