iPhone Application Development : Creating a Multi-View Toolbar Application (part 2) - Instantiating the View Controllers

Instantiating the View Controllers

Your project should now contain content for each of the views and all the view controller classes it needs to function. The classes, however, still need to be instantiated so that we have actual view controllers and view objects to use in the application.

Open MultipleViewsViewController.xib in Interface Builder. This file contains the parent view that we will be using to for the toolbar interface element, and it is also a logical place to add our other view controller instances.

Using the Library (Tools, Library), drag a view controller (UIViewController) into the Document window. We want this view controller to be an instance of our FirstViewController class. With the controller selected, press Command+4 to open the Identity Inspector. Use the drop-down menu to choose FirstViewController, as shown in Figure 5.

Figure 5. Update the view controllers to point to the classes you created earlier.

Next, the view controller must be updated to point to the correct XIB file (FileViewController.xib) for its view. Select the controller in the Document window and press Command+1 to open the Attributes Inspector. Within the NIB Name drop-down menu, choose FirstViewController, as shown in Figure 6.

Figure 6. Associate every view controller with the appropriate XIB file.

Repeat these steps for the SecondViewController and ThirdViewController classes. (That is, add a new view controller instance, set the class, and associate the view.) When finished, your MultipleViewsViewController.xib should look very similar to Figure 7.

Figure 7. Add three view controller instances to the XIB file.

With these changes, our project will build and instantiate the controllers, but there is still no way of displaying the different views. It’s time to add the toolbar controls and code to make that happen!