extension UIView {
func addFitConstraints(to: UIView) {
to.translatesAutoresizingMaskIntoConstraints = false
self.addConstraint(NSLayoutConstraint(item: to,
attribute: .top,
relatedBy: .equal,
toItem: self,
attribute: .top,
multiplier: 1.0,
constant: 0))
self.addConstraint(NSLayoutConstraint(item: to,
attribute: .leading,
relatedBy: .equal,
toItem: self,
attribute: .leading,
multiplier: 1.0,
constant: 0))
self.addConstraint(NSLayoutConstraint(item: self,
attribute: .bottom,
relatedBy: .equal,
toItem: to,
attribute: .bottom,
multiplier: 1.0,
constant: 0))
self.addConstraint(NSLayoutConstraint(item: self,
attribute: .trailing,
relatedBy: .equal,
toItem: to,
attribute: .trailing,
multiplier: 1.0,
constant: 0))
}
}
let superView = UIView()
let subView = UIView()
superView.addSubview(subView)
superview.addFitConstraints(to: subView)