iOS 面试题与答案

问题 16. What is Method Swizzling?

The process of changing the implementation of an existing domain, Method Swizzling, enables you to write that code that can be executed before or after the original method.

问题 17. When is the category used?

 It is used to add a set of related methods and to add additional methods in the Cocoa framework.

问题 18. What is the difference between Viewdidload and Viewdidappear?

Viewdidload:

• It is called when it is loaded into memory.
• Data can be loaded in Viewdidload if it is fairly static and likely to change.

Viewdidappear:

• It is called when the view is visible and presented on the device.
• You can perform any layout functions or draw in the UI.

问题 19. What does KVO stand for?

KVO means key-value observing, which enables a controller to observe changes to property value.

问题 20. Which JSON framework is supported by iOS (iPhone OS)?

• SBJson framework is supported by iOS. It is a JSON parser and generator for Objective-C (Objective-C is the primary programming language we use when writing software for OS X and iOS. It is a superset of the C programming language and provides object-oriented capabilities and a dynamic runtime).
• SBJson provides flexible APIs and additional control that makes JSON handling easy.