What is an undefined macro?

Question

I am learning objective-C and Cocoa. In an Apple tutorial, I look over there a note that says:

IBOutlet is a zero-value macro that the C preprocessor deletes at compile time.

I am wondering - what is the macro defining zero?

Answer 1

#define IBOutlet

Whenever an IBOutlet is used in the program text, it will not be replaced with anything at all.

Answer 2

FYI, , , IBOutlet, , Interface Builder . (, , ), , IBOutlet, Outlet Interface Builder .

Answer 3

- , ( ) . - - , :

#define IN
#define OUT
#define INOUT

int myFunction(IN char *name, INOUT char *address, OUT char *phone);

, name , address , , phone .

Answer 4

Also - if you do not know how something is defined - the command double-click on it, and Xcode will open the definition in the original source file.

Answer 5

Oh, and while I am. Parallel double-click (attempt) will open the documentation for double-click.