How can I make a button have a rounded border in Swift?

I'm building an app using swift in the latest version of Xcode 6, and would like to know how I can modify my button so that it can have a rounded border that I could adjust myself if needed. Once that's done, how can I change the color of the border itself without adding a background to it? In other words I want a slightly rounded button with no background, only a 1pt border of a certain color.

Use button.layer.cornerRadius, button.layer.borderColor and button.layer.borderWidth. Note that borderColor requires a CGColor, so you could say (Swift 3/4):

button.backgroundColor = .clear
button.layer.cornerRadius = 5
button.layer.borderWidth = 1
button.layer.borderColor = UIColor.black.cgColor

To do this job in storyboard (Interface Builder Inspector)

With help of IBDesignable, we can add more options to Interface Builder Inspector for UIButton and tweak them on storyboard. First, add the following code to your project.

@IBDesignable extension UIButton {

    @IBInspectable var borderWidth: CGFloat {
        set {
            layer.borderWidth = newValue
        }
        get {
            return layer.borderWidth
        }
    }

    @IBInspectable var cornerRadius: CGFloat {
        set {
            layer.cornerRadius = newValue
        }
        get {
            return layer.cornerRadius
        }
    }

    @IBInspectable var borderColor: UIColor? {
        set {
            guard let uiColor = newValue else { return }
            layer.borderColor = uiColor.cgColor
        }
        get {
            guard let color = layer.borderColor else { return nil }
            return UIColor(cgColor: color)
        }
    }
}

Then simply set the attributes for buttons on storyboard.