You use Interface Builder to create storyboard files for your application. Most applications need only one storyboard file, but you can create multiple storyboard files if you want. Every storyboard file has a view controller known as the initial view controller. This view controller represents the entry point into the storyboard. For example, in your application’s main storyboard file, the initial view controller would be the first view controller presented by your application.
Each view controller in a storyboard file manages a single scene. For iPhone applications, a scene manages one screen’s worth of content, but for iPad applications the content from multiple scenes can be on screen simultaneously. To add new scenes to your storyboard file, drag a view controller from the library to the storyboard canvas. You can then add controls and views to the view controller’s view just as you would for a nib file. And as before, you can configure outlets and actions between your view controller and its views.
When you want to transition from one view controller to another, Control-click a button, table view cell, or other trigger object in one view controller, and drag to the view controller for a different scene. Dragging between view controllers creates a segue, which appears in Interface Builder as a configurable object. Segues support all of the same types of transitions available in UIKit, such as modal transitions and navigation transitions. You can also define custom transitions and transitions that replace one view controller with another.
Preparing to Transition to a New View Controller
Whenever a user triggers a segue in the current scene, the storyboard runtime calls the prepareForSegue:sender: method of the current view controller. This method gives the current view controller an opportunity to pass any needed data to the view controller that is about to be displayed. When implementing your view controller classes, you should override this method and use it to handle these transitions.
Presenting Storyboard View Controllers Programmatically
Although the storyboard runtime usually handles transitions between view controllers, you can also trigger segues programmatically from your code. You might do so when setting up the segue in Interface Builder is not possible, such as when using accelerometer events to trigger the transition. There are several options for transitioning to a new view controller:
- If a storyboard file contains an existing segue between the current view controller and the destination view controller (perhaps triggered by some other control in the view controller), you can trigger that segue programmatically using the performSegueWithIdentifier:sender:method of UIViewController.
- If there is no segue between the view controllers but the destination view controller is defined in the storyboard file, first load the view controller programmatically using the instantiateViewControllerWithIdentifier: method of UIStoryboard. Then present the view controller using any of the existing programmatic means, such as by pushing it on a navigation stack.
- If the destination view controller is not in the storyboard file, create it programmatically and present it as described in View Controller Programming Guide for iOS.