Learing Web Links

http://www.tutorialspoint.com/objective_c/objective_c_protocols.htm

categories in ios tutorial 

http://code.tutsplus.com/tutorials/objective-c-categories--mobile-10648

http://www.icodeblog.com/2010/11/04/an-introduction-to-categories-part-1-of-2/

http://rypress.com/tutorials/objective-c/blocks.html