SWIFT

swift add width/height constraint to view

// Swift3+
let imageView = UIImageView()
imageView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
  imageView.widthAnchor.constraint(equalToConstant: 16),
  imageView.heightAnchor.constraint(equalToConstant: 16),
])
self.addSubview(self.imageView)