create a loop to add 40 everytime a value is called

Question

I am positioning 3 uibttons with the same height and wideth and same x value the only thing I want change is that I want each uibutton added 40 positivie it to seperate it. I would think there is some way to do this with a loop instead of doing this manually like i did below. I want (equalTo: view.centerYAnchor, constant : 0), to be replaced with yP plus 40 everytime it is called.

   var yP = 0


    undoButton.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :25),
       undoButton.topAnchor.constraint(equalTo: view.centerYAnchor, constant : 0),
       undoButton.widthAnchor.constraint(equalToConstant: CGFloat(widthBox)),
       undoButton.heightAnchor.constraint(equalToConstant: 20),

       clearButton.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :25),
       clearButton.topAnchor.constraint(equalTo: view.centerYAnchor, constant : 40),
       clearButton.widthAnchor.constraint(equalToConstant: CGFloat(widthBox)),
       clearButton.heightAnchor.constraint(equalToConstant: 20),

       color.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :25),
       color.topAnchor.constraint(equalTo: view.centerYAnchor, constant : 80),
       color.widthAnchor.constraint(equalToConstant: CGFloat(widthBox)),
       color.heightAnchor.constraint(equalToConstant: 20),

Answer 1

Try this.

func setConstraints() {
    var yPosition: CGFloat = 0

    [undoButton, clearButton, color].forEach { button in
        NSLayoutConstraint.activate([
            button.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :25),
            button.topAnchor.constraint(equalTo: view.centerYAnchor, constant : yPosition),
            button.widthAnchor.constraint(equalToConstant: CGFloat(widthBox)),
            button.heightAnchor.constraint(equalToConstant: 20)
        ])
        yPosition += 40
    }
}