Using Standard Types
In this section, you are going to experiment with standard types in an Xcode playground. A playground lets you write code and see the results without the overhead of manually running an application and checking the output.
In Xcode, select File → New → Playground.... You can accept the default name for this file; you will only be here briefly. Make sure the platform is iOS (Figure 2.2).
Figure 2.2 Configuring a playground
Click Next and save this file in a convenient place.
When the file opens, notice that the playground is divided into two sections (Figure 2.3). The larger white area to the left ...