Question

Until now, I would like to know the difference between these 2. I always been using instance methods but have no idea the meaning behind it. Can anyone explain in the simplest way? Thanks.

Answer 1

Class methods are called on the classes themselves, like this:

[NSDate date];
// declared as: + (NSDate *)date;

Instance methods are called on actual objects:

NSDate *date = ...;
[date timeIntervalSinceNow];
// declared as: - (NSTimeInterval)timeIntervalSinceNow;

Read the The Objective-C Programming Language guide for more information.