An action is a piece of code that’s linked to some kind of event that can occur in your app. When that event takes place, the code gets executed. You can define an action to accomplish anything from manipulating a piece of data to updating the user interface. You use actions to drive the flow of your app in response to user or system events.
You define an action by creating and implementing a method with an
IBAction return type and a
sender parameter points to the object that was responsible for triggering the action. The
IBAction return type is a special keyword; it’s like the
void keyword, but it indicates that the method is an action that you can connect to from your storyboard in Interface Builder (which is why the keyword has the
Outlets provide a way to reference objects from your interface—the objects you added to your storyboard—from source code files. You create an outlet by Control-dragging from a particular object in your storyboard to a view controller file. This creates a property for the object in your view controller file, which lets you access and manipulate that object from code at runtime. For example, in the second tutorial, you’ll create an outlet for the text field in your ToDoList app to be able to access the text field’s contents in code.
Outlets are defined as
@property (weak, nonatomic) IBOutlet UITextField *textField;
IBOutlet keyword tells Xcode that you can connect to this property from Interface Builder.