constraints.swift

func constrainToEdges(of view: UIView) {
    translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        leftAnchor.constraint(equalTo: view.leftAnchor),
        topAnchor.constraint(equalTo: view.topAnchor),
        rightAnchor.constraint(equalTo: view.rightAnchor),
        bottomAnchor.constraint(equalTo: view.bottomAnchor)
    ])
}

func constrainToCenter(of view: UIView) {
    translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        centerXAnchor.constraint(equalTo: view.centerXAnchor),
        centerYAnchor.constraint(equalTo: view.centerYAnchor),
    ])
}

func constrain(to size: CGSize) {
    translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        widthAnchor.constraint(equalToConstant: size.width),
        heightAnchor.constraint(equalToConstant: size.height),
    ])
}