Hi All,

You can add auto layout constraints by using Storyboard Interface OR by adding constraints dynamically. There are three ways to add constraint dynamically (as per Apple Inc.)

NSLayoutConstraint is one of the way is used to add autolayout constraints dynamically.

NSLayoutConstraint Example :-

let new_view:UIView! = UIView(frame: CGRectMake(20, 20, 100, 100));
        new_view.backgroundColor = UIColor.redColor();
        new_view.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(new_view);


        NSLayoutConstraint(item: new_view,
            attribute: .Leading,
            relatedBy: .Equal,
            toItem: view,
            attribute: .LeadingMargin,
            multiplier: 1.0,
            constant: 0.0).active = true
        NSLayoutConstraint(item: new_view,
            attribute: .Top,
            relatedBy: .Equal,
            toItem: view,
            attribute: .TopMargin,
            multiplier: 1.0,
            constant: 20.0).active = true
        NSLayoutConstraint(item: new_view,
            attribute: .Height,
            relatedBy: .Equal,
            toItem: new_view,
            attribute:.Width,
            multiplier: 2.0,
            constant:0.0).active = true

        NSLayoutConstraint(item: new_view,
            attribute: .Width,
            relatedBy: .Equal,
            toItem: nil,
            attribute: .NotAnAttribute,
            multiplier: 1.0,
            constant: 100.0).active = true