Cocoa Programming for OS X: The Big Nerd Ranch Guide

For the More Curious: Which Object Sends the Action Message?

The target on the Cut, Copy, and Paste menu items is nil. Sending a message to nil will not do anything. All target-action messages are handled by NSApplication. It has the following method:

 ​ ​ ​ ​f​u​n​c​ ​s​e​n​d​A​c​t​i​o​n​(​_​:​ ​S​e​l​e​c​t​o​r​,​ ​t​o​:​ ​A​n​y​O​b​j​e​c​t​!​,​ ​f​r​o​m​:​ ​A​n​y​O​b​j​e​c​t​!​)​ ​-​>​ ​B​o​o​l​

When the target is nil, NSApplication knows to try to send messages to the objects in the responder chain.