Hi,
Just became an iPhone developer. I'm completely new to this, and not really sure whether I should start learning SDK version 3.2 or 4.0. I found tons of videos and tutorials for 3.2, not a lot for 4.0.
So shall I start with 3.2 and then worry about 4.0 later? or am I going to have to re-learn many things that I will learn in 3.2?
Your input is much appreciated. :)
What's your time frame? The vast majority of content will not change at all - if you're interested, there's absolutely no reason to not start now.
Further, even if the API that you're working on changes, understanding how they used to do things, and why they changed is a valuable bit of knowledge (you can download the iPhone 4.0 SDK now in beta, and manually compare if you'd like).
Finally, Apple is notorious about delaying release of final documentation - I would definitely not take a dependency on when they ship it to start learning.
You will not have to learn very many new things. The base SDK is very much the same, and nearly every method is backwards compatible. The basic design patterns of iPhone app architecture have not changed and thus, you can start learning on 3.1.3 or 3.2 and catch up whenever you have access to 4.0 (now if you are in the paid developer program).
The only thing to be aware of is that 3.2 has some iPad specific things, most of it will apply to iPhone OS 4.0.
I think that you should start by now. Understating basics as design patterns, architectural commons and styles of programming for iPhone. I think this is better if you acquire some practice now with little APIs to learn that latter.
APPLE has a very strong emphasis on making SDKs solid and very extensible since the beginning and not doing radical changes over the time (Open/Close Principle).
I encourage you learn, not only iPhone SDK or CocoaTouch, but to acquire a deep understanding of Objective C.