NSLayoutConstraint class has been Apple’s recommendation for layout, as they create relationships between views, parent views, and child views, therefore explicitly setting the
frame property is not needed. This also has benefits of helping with accessibility, multiple device screen size support, and helping with views in different orientations. I’m little late to the party with iOS 9’s
NSLayoutAnchor, which simplifies the wordy
NSLayoutConstraint instantiation, with a simple-to-use API.