You can set background color of view to the UIColor with alpha, and not affect view.alpha:
view.alpha
view.backgroundColor = UIColor(white: 1, alpha: 0.5)
or
view.backgroundColor = UIColor.red.withAlphaComponent(0.5)
Setting alpha property of a view affects its subviews. If you want just transparent background set view's backgroundColor proprty to a color that has alpha component smaller than 1.
alpha
backgroundColor
view.backgroundColor = UIColor.white.withAlphaComponent(0.5)
For Swift 4.x and above
yourView.backgroundColor = UIColor.black.withAlphaComponent(0.5)
This works for me.
It may help you. Happy coding :)