What describes an "Outlet" best in objective-c / Cocoa?

Question

Can someone explain in an humanly understandable way what an "Outlet" is?

Answer 1

It's an instance variable that shows up in Interface Builder, so that you can use IB to plug another object into the outlet.

When you load the nib, the nib-loading system will do the requisite magic to make sure the right object shows up in each outlet.

Edit: I'd intended to write a full blog post around this image (I changed my mind after finishing the image), but even alone, it should help clarify outlets for people. Here you go:

_{(source: boredzo.org)}

Answer 2

From a code point-of-view and IBOutlet is only a hint for Interface Builder. It's actually a macro that compiles to, well, nothing at all. That is, the compiler completely removes when compiling.

But Interface Builder can scan your code for IBOutlet so when you right-click on an object in IB you can see all the outlets that you could connect to other objects.

alt text http://img27.imageshack.us/img27/5512/picture820090228.png

In this example, delegate is a member variable of UIApplication and it is an IBOutlet too.