Objective-C method description (doc comments)

What you are describing are called “documentation comments”, or “doc comments” for short.

Xcode, as of version 4.6.3, does not display your own doc comments in a pop-up window or its quick help inspector. You have to compile your comments into a “docset” to get Xcode to display them. There are tools to do that, but there is no way to get Xcode to reload a docset except by quitting and restarting it, so I don't recommend bothering.

Xcode 5 (which is currently available as a developer preview for paid members of the OS X and iOS developer programs) does display the doc comments for your own code; see “Quick Help” on the Developer Tools Features page. You must write the doc comments in the header file. You may use either doxygen or headerdoc format.

Update: The format below works for Objc. If you want to document swift code, refer to NSHipster's blog about Swift Documentation

The Xcode 5 can do what you want. Thanks to Wonil Kim, in the .h file:

/** 
 * Add new message between source to destination timeline as empty name string
 * @author Wonil Kim
 *
 * @param sourceId Source timeline entity ID
 * @param destId Destination timeline entity ID
 * @return A newly created message instance
 */
- (ISMessage*)messageFromTimeline:(NSInteger)sourceId toTimeline:(NSInteger)destId;

Once this is done, you can alt+click on the method name, and.. voilà!

Of course, as you can see on Kim's blog, this is not the only way:

/*! Some description of the method....
 * \returns  The result
 */

Alternatively,

/// Some description to show up, done by:
/// @author  Olly Dixon

You got the point...

As many already have mentioned, Objective-C does not show you your documentation; in fact, neither does java (javadoc, may be). It's your IDE, in this case, the un-crashable Xcode :)

UPDATE2: Complete list of "Special Commands" in comments.

UPDATE3: Use VVDocumenter-Xcode if you'd like to enable auto-generation of documentation by ///.

UPDATE4:: VVDocumenter has be integrated in to Xcode:

Use the shortcut (⌥ Option + ⌘ Command + /) to add a documentation comment to your code if you are using Xcode 8 or above