Remember the Model-View-Controller architecture you read about in Chapter 26? You have already created a view (your storyboard and UI elements) and a controller (your ViewController class). At this point, however, you do not have a model. Create a Cocoa Touch class by selecting File → New → File.... With iOS selected at the top, select Cocoa Touch Class from the Source section (Figure 27.18).
Figure 27.18 Creating a new Cocoa Touch class