If you are just starting with Objective C, but have some backgrounds with most of the things about OOP, then you can probably start with Objective C. However,
there is a catch: there are some concepts such as memory management, etc. that have originated with C.
Right now, in my current situation, with the book that I bought called
The iOS 5 Developer's Cookbook by Erica Sadun (which is, by the way, I really good book for iOS programming), it talks about memory management with Core Foundation, and just the overall concept of memory management was just really hard for me to grasp the idea.
My situation just goes to show that there are some concepts that requires C knowledge (obviously Obj. C is a strict superset of C).
So my two suggestions are:
1) If you
have a pretty good solid foundation of Object Oriented Programming and some languages that implement OOP (e.g. Java), then you can get-by starting with Objective C right away. Your knowledge of such language will help you somewhat to learn Objective C, but many ideas are new there so watch out for that.
2) If you
don't have enough knowledge about OOP and have not looked up OOP-based languages, then I suggest going with C first then learn some OOP concepts, then start with Obj. C. Many books will guide you through the concepts of OOP, so you'll be able to start programming with Objective C in no time.
Hope this helps. Cheers.
