Objective-C Programming: The Big Nerd Ranch Guide

A note about comments

As you type in exercises, do not be shy about adding comments of your own to help you remember what code is doing. Get in the habit of commenting code. Write useful and specific comments that could be understood by someone else reading your code or by you in the future coming back to review the code.

Comments can be helpful when you tackle challenges. For example, say you get a challenge working but are not sure it is solved in an elegant way. Leave yourself a note about what bugged you. When you are further along in the book, review old challenges and see if you can improve your solutions. This will also test your ability to write useful comments. Something like

// Not sure if this is right
...

will be useless ...