Simple function that adds a child view and its constraints

addSubView.swift

    func addChildView(_ childView: UIView, to containerView: UIView) {
        containerView.addSubview(childView)
        childView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint(item: childView,
                           attribute: .leading,
                           relatedBy: .equal,
                           toItem: containerView,
                           attribute: .leading,
                           multiplier: 1.0,
                           constant: 0.0).isActive = true
        
        NSLayoutConstraint(item: childView,
                           attribute: .trailing,
                           relatedBy: .equal,
                           toItem: containerView,
                           attribute: .trailing,
                           multiplier: 1.0,
                           constant: 0.0).isActive = true
        
        NSLayoutConstraint(item: childView,
                           attribute: .top,
                           relatedBy: .equal,
                           toItem: containerView,
                           attribute: .top,
                           multiplier: 1.0,
                           constant: 0.0).isActive = true
        
        NSLayoutConstraint(item: childView,
                           attribute: .bottom,
                           relatedBy: .equal,
                           toItem: containerView,
                           attribute: .bottom,
                           multiplier: 1.0,
                           constant: 0.0).isActive = true
    }