a.swift

public extension NSLayoutConstraint {
    
    /// Disable auto resizing mask and activate constraints
    ///
    /// - Parameter constraints: constraints to activate
    static func on(_ constraints: [NSLayoutConstraint]) {
        constraints.forEach {
            ($0.firstItem as? UIView)?.translatesAutoresizingMaskIntoConstraints = false
            $0.isActive = true
        }
    }
    
    static func on(_ constraintsArray: [[NSLayoutConstraint]]) {
        let constraints = constraintsArray.flatMap({ $0 })
        NSLayoutConstraint.on(constraints)
    }
}