Programming in Objective-C 2.0 (2nd Edition)

One book you should pick up right off the hop is Kochan. The most highly recommended book introducing people to Objective-C. In addition, there are loads of videos and sample code on developer.apple.com.

What's the best (and easiest) documentation to start with?

I found this link (for PHP programmers): http://mohrt.blogspot.com/2008/10/objective-c-crash-course-for-php.html Otherwise go with books, and use xCode and read code.

Learn Objective - C: (Programming Objective C 2.0) - http://www.amazon.com/Programming-Objective-C-2-0-Stephen-Kochan/dp/0321566157/ref=sr_1_1?ie=UTF8&qid=1298891453&sr=8-1

Learn iOS coding: (Big Nerd Ranch) http://www.amazon.com/iPhone-Programming-Ranch-Guide-Guides/dp/0321706242/ref=sr_1_1?ie=UTF8&s=books&qid=1298891484&sr=1-1

Is it that easy for me (as a beginner objective-c developer) to attract customers on AppStore and get them to buy my IOS apps, or is there a huge competition among experts on AppStore so that there is no chance for beginners on AppStore?

If your idea is good and your app is well written sure. But there are a few competitors.

If there is any chance to sell my apps on AppStore, what's the possible profit for them on AppStore ?

There is no easy answer to your question here, but you will have a profit from apple with 70% of the product prize.

Good luck out there.

In the closest book to me presently, they are called "property attributes" http://www.amazon.com/Programming-Objective-C-2-0-2nd-Edition/dp/0321566157

A quick search of Apple's docs yields the same word: https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html

And finally, the link to the specific section of the docs, which uses both "attributes" and your very own "keywords": https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html#//apple_ref/doc/uid/TP30001163-CH17-SW2

I fully recommend viewing this site, as I have heard many good things of it:

http://cocoadevcentral.com/d/learn_objectivec/

If you're more the pick it up and read kind of person, might I suggest the following book:

http://www.amazon.com/Programming-Objective-C-2-0-Stephen-Kochan/dp/0321566157/ref=sr_1_1?ie=UTF8&qid=1305617578&sr=8-1

Third edition will be out next month, so you may want to wait on it.

Assuming that you're calling myMethod on the same class as what implements viewDidLoad:

- (void)viewDidLoad {
    //...other code
    [self myMethod];
    //...other code
}

If you are having trouble with basic Objective-C though, I'd strongly suggest to either get a decent book on Objective-C, such as:

• Programming in Objective-C 2.0 by Stephen Kochan
• Cocoa Programming for Mac OS X by Aaron Hillegass
• iPhone Programming: The Big Nerd Ranch Guide by Joe Conway & Aaron Hillegass

…or at least read a good beginners tutorial, such as:
http://www.cocoadevcentral.com/d/learn_objectivec/

There are quite a few more helpful beginners tutorials by Scott Stevenson here:
http://www.cocoadevcentral.com/

I agree, Cocoa Programming for Mac OS X by Aaron Hillegass is a great book to learn Cocoa, and it covers Obejctive-c nicely, but if you really want to KNOW the language, I would recommend: Programming in Objective-C 2.0: http://www.amazon.com/Programming-Objective-C-2-0-Developers-Library/dp/0321566157

Both are fantastic books and nicely complement eachother.

Its very important to remember that other people are having a hard time learning Cocoa too. Reading Aaron's book is a fantastic way to start. Reading source code is also another great way. THere is some open source iPhone projects (for example: wordpress), and there a bunch for OS X. Read what other people are doing so you can get the flow of an application. I found that to be the hardest part about learning (especially the Cocoa part).