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You can show a loading spinner, a UIActivityIndicatorView, within a UIButton, that can be showed and hidden and also changes the button's alpha and interactivity.

First create an extension, then add a UIActivityIndicatorView to the button, half its alpha value and disable the button on loading. And then do the opposite when we stop the loading:

extension UIButton {
    func loadingIndicator(_ show: Bool) {
        let tag = 808404
        if show {
            self.isEnabled = false
            self.alpha = 0.5
            let indicator = UIActivityIndicatorView()
            let buttonHeight = self.bounds.size.height
            let buttonWidth = self.bounds.size.width
            indicator.center = CGPoint(x: buttonWidth/2, y: buttonHeight/2)
            indicator.tag = tag
            self.addSubview(indicator)
            indicator.startAnimating()
        } else {
            self.isEnabled = true
            self.alpha = 1.0
            if let indicator = self.viewWithTag(tag) as? UIActivityIndicatorView {
                indicator.stopAnimating()
                indicator.removeFromSuperview()
            }
        }
    }
}

Stolen from [here] (http://stackoverflow.com/questions/15269264/place-a-uiactivityindicator-inside-a-uibutton/39504623#39504623).