UIAppearance Protocol Reference

Overview

You use the UIAppearance protocol to get the appearance proxy for a class. You customize the appearance of instances of a class by sending appearance modification messages to the class’s appearance proxy.

There are two ways to customize appearance for objects: for all instances, and for instances contained within an instance of a container class.

• To customize the appearance of all instances of a class, you use appearance to get the appearance proxy for the class. For example, to modify the tint color for all instances of UINavigationBar:

  [[UINavigationBar appearance] setTintColor:myColor];

• To customize the appearances for instances of a class when contained within an instance of a container class, or instances in a hierarchy, you use appearanceWhenContainedIn: to get the appearance proxy for the class:

  [[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], nil]

  setTintColor:myNavBarColor];

  [[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], [UIPopoverController class], nil]

  setTintColor:myPopoverNavBarColor];

  [[UIBarButtonItem appearanceWhenContainedIn:[UIToolbar class], nil]

  setTintColor:myToolbarColor];

  [[UIBarButtonItem appearanceWhenContainedIn:[UIToolbar class], [UIPopoverController class], nil]

  setTintColor:myPopoverToolbarColor];

In any given view hierarchy, the outermost appearance proxy wins. Specificity (depth of the chain) is the tie-breaker. In other words, the containment statement in appearanceWhenContainedIn: is treated as a partial ordering. Given a concrete ordering (actual subview hierarchy), UIKit selects the partial ordering that is the first unique match when reading the actual hierarchy from the window down.

To support appearance customization, a class must conform to the UIAppearanceContainer protocol and relevant accessor methods must be marked with UI_APPEARANCE_SELECTOR.

Class Methods