An extension to help center image and title in UIButton. The position of the image and title can be reversed.

Extension.swift

extension UIButton {

    func alignHorizontal(spacing: CGFloat, imageFirst: Bool) {
        let edgeOffset = spacing / 2
        imageEdgeInsets = UIEdgeInsets(top: 0,
                                       left: -edgeOffset,
                                       bottom: 0,
                                       right: edgeOffset)
        titleEdgeInsets = UIEdgeInsets(top: 0,
                                       left: edgeOffset,
                                       bottom: 0,
                                       right: -edgeOffset)

        if !imageFirst {
            self.transform = CGAffineTransform(scaleX: -1, y: 1)
            imageView?.transform = CGAffineTransform(scaleX: -1, y: 1)
            titleLabel?.transform = CGAffineTransform(scaleX: -1, y: 1)
        }

        // increase content width to avoid clipping
        contentEdgeInsets = UIEdgeInsets(top: 0, left: edgeOffset, bottom: 0, right: edgeOffset)
    }

}