to separate the code handling the data and the user interface. The link between the data and UI is usually done in a controller, or, in iOS, a view controller. In most projects, view controllers are interconnected and can be very dependent with one another. That’s where the flow controller comes in. It serves as a link between view controllers. It’s the brain of the app. Quote: https://ocollet.com/2014/02/06/flow-controller/