In Objective-C, a category is a group of related methods for a class, and all of the methods defined in a category are available through the class as if they were defined in the main interface file. Instead of the normal @interface declaration, we include the category name in (...) after the class name we're extending.

Which one is not a property of NSError class?

Exceptions can be handled using the standard a common pattern found in most other high-level programming languages

Two distinct types of problems can arise while an iOS or OS X application is running.

In Objective-C programming, error handling is provided with (...) class available in Foundation framework.

(...) is an abstractClass which represents a stream of data. They are used in Archiving and Unarchiving objects. (...) objects are usually used in a method that is being implemented so that the class conforms to the protocol.

What is the id type?

What is the C type used to work with objects in Obj-C?

What will be logged? int x = 1; __block int y = 1; void (^test)(void) = ^{ NSLog(@"%i, %i", x, y); }; x = 2; y = 2; test();

What is true regarding messaging?

Which of the following is the fastest?