No 2. Cocoalab Tutorial
Coming on to some online and free guide for Xocde (finally!), something that stands out is this PDF from Cocoalab. Available in 10 different languages, this e-book covers it all from variables to modulus and from pointers to memory management.
Click here to get it (English)
No 1. Lynda Xcode Tutorials
This is a premium source for Xcode and is the best one available on the internet. It will cost you $25/month to $375/year depending on your subscription but you can rest assured that you won’t be needing any other resource once you invest; Lynda offers a toll-free phone number, international telephone number, and email submission form for technical support or to answer your questions in addition to already available help files.
As an additional resource you can always use the free and amazing StackExchange for your more specific queries.
