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Defined in <AppKit/NSNibDeclarations.h> as

#ifndef IBAction #define IBAction void #endif

Used as void and serves to alert Interface Builder that said message is an action for target/action connections.


@interface className { //… }

Note: Interface Builder may not recognize the action if you put a space between (IBAction) and the method name in your header file. (I have never seen this, and I almost always put some whitespace after (IBAction). Thus maybe this pertains to an older version of IB that predates Xcode? –GrahamCox)

See also IBOutlet.


Does anybody else feel that this is slightly clumsy compared to the rest of ObjectiveC? Sure, it’s marginally convenient, but it goes against the standard form of a function. Creating synonyms for void seems dangerous, at least to me; a newcomer would think that the method returned some form of action. At least IBOutlet is used in the same way as other variable modifiers. –JediKnil

Any newcomer should of course read ObjC.pdf, or whatever the file is now; IIRC that file describes the use of IBAction. Nonetheless, it is a bit curious.

In the “Fundamentals of Cocoa” session at WWDC 2004, the presenter indicated that IBAction was not needed in most cases for IB to notice a method as an action. Simply having the correct signature (returning void with a single id parameter) is sufficient. I have not been able to find any corroborating documentation, but I can confirm that IB seems to recognize my actions just fine even when I don�t tag them with IBAction. –KevinYank