Comment by melling

Instead of this format,

    Col.topAnchor.constraint(equalTo: topAnchor, constant: 0).isActive = true           
    Col.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0).isActive = true
    Col.leftAnchor.constraint(equalTo: leftAnchor, constant: 0).isActive = true
    Col.rightAnchor.constraint(equalTo: rightAnchor, constant: 0).isActive = true

I prefer:

NSLayoutConstraint.activate([

    Col.topAnchor.constraint(equalTo: topAnchor, constant: 0), 
    Col.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0),  
    Col.leftAnchor.constraint(equalTo: leftAnchor, constant: 0),      
    Col.rightAnchor.constraint(equalTo: rightAnchor, constant: 0),

])

GitHub example with better readability:

https://github.com/melling/ios_topics/tree/master/ButtonCent...