A wonderful layout component called the UIStackView was introduced with iOS 9. With this component it is really easy to layout components in a row both horizontally and vertically. Apple recommends using the UIStackView wherever possible and resort to explicit NSLayoutConstraints only when there is no way to do it with UIStackView. This saves you lots of boiler plate NSLayoutConstraint creation code.
UIStackView requires iOS 9, but we’re not ready to make our apps require iOS 9+ just yet. In the meanwhile, we developers are eager to try this component in our apps right now! This is why I created this replica of the UIStackView, called the TZStackView (TZ = Tom van Zummeren, my initials). I created this component very carefully, tested every single corner case and matched the results against the real UIStackView with automated XCTestCases.