Dingi Maps SDK for iOS
The Dingi Maps SDK for iOS is an open-source framework for embedding interactive map views with scalable, customizable vector maps on iOS 9.0 and above using Objective-C, Swift, or Interface Builder. It takes stylesheets that conform to the DingiMap Style Specification, applies them to vector tiles that conform to the DingiMap Vector Tile Specification, and renders them using OpenGL.

DingiMap Reference