set constraints for UIView swift
view.addSubview(myView1)
myView1.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
myView1.centerXAnchor.constraint(equalTo: view.centerXAnchor),
myView1.centerYAnchor.constraint(equalTo: view.centerYAnchor),
myView1.widthAnchor.constraint(equalToConstant: 100),
myView1.heightAnchor.constraint(equalToConstant: 100),
])
# OR
view.addSubview(myView2)
myView2.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
myView2.leadingAnchor.constraint(equalTo: view.leadingAnchor,constant: 16),
myView2.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor,constant: 16),
myView2.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.3),
myView2.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.3)
])