Objective-C files can include header files by using the standard C #include preprocessor directive or by using the Objective-C #import preprocessor directive. The #import directive is similar to the #include directive. #import assures that no file is imported more than once. Objective-C header files that are imported don�t need to be surrounded by �guards� (usually implemented with #define, #ifndef, and #endif) to keep them from being included multiple times. You should use the #import directive to import Cocoa headers because the Cocoa headers may not contain guards.

What is #import ?

It’s a C preprocessor construct to “include” the textual content of another file while automatically avoiding multiple inclusions of the same file.

#import

is an alternative to

#include

If #include is used, the included file must provide “guards” such as the following to prevent multiple inclusions:

#ifndef OBJECT_H … #define OBJECT_H #endif