Simplest solution:
iOS 10 & up, Swift:
***button.transform = CGAffineTransform(scaleX: -1.0, y: 1.0)
button.titleLabel?.transform = CGAffineTransform(scaleX: -1.0, y: 1.0)
button.imageView?.transform = CGAffineTransform(scaleX: -1.0, y: 1.0)***
Before iOS 10, Swift/Obj-C:
***button.transform = CGAffineTransformMakeScale(-1.0, 1.0);
button.titleLabel.transform = CGAffineTransformMakeScale(-1.0, 1.0);
button.imageView.transform = CGAffineTransformMakeScale(-1.0, 1.0);***
iOS 9 & up, Swift: (Recommended)
***button.semanticContentAttribute = .forceRightToLeft***