(...) are used by Cocoa and Cocoa Touch objects for a variety of different situations. For example, the table view classes (NSTableView for OS X and UITableView for iOS) both use a data source object to supply them with the necessary information. Both define their own data source (...); both table view classes also allow you to set a delegate object, which again must conform to the relevant NSTableViewDelegate or UITableViewDelegate (...). The delegate is responsible for dealing with user interactions, or customizing the display of certain entries.

If you start a class definition that conforms to a specified (...), you will not need to relist all the methods you will implement for that protocol in the @interface section.

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.

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.

Output of the following code?

What is a SEL?

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();