At this point you should be somewhat familiar with using Swift’s standard types: strings, arrays, enums, etc. It is time to move on to bigger and better things: defining your own types. In this chapter, you will build a simple 2D physics simulation. You will create your own structure and a few classes, and you will learn about the differences between them.
In Cocoa, structures are typically used to represent groupings of data. For example, there is NSPoint, which represents a point in 2D space with an X and a Y value. As your first structure you will create a 2D vector structure.
Create a new playground. From Xcode’s File menu, select New... → Playground. Name the playground Physics