Constrainable.swift

protocol Constrainable {}

extension Constrainable where Self: UIView {
    
    @discardableResult
    func constrain(constraints: (Self) -> [NSLayoutConstraint]) -> [NSLayoutConstraint] {
        let constraints = constraints(self)
        self.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate(constraints)
        return constraints
    }
    
}

extension UIView: Constrainable {}