Understanding through diagrams

[Epicurus]

Hello all,
I'm a graphic designer and new to programming, though I have learned HTML. I would like to develop an iPhone app eventually so decided to start with Objective-C. I find this book very good but I have a block in my thinking which I'd like to get some thoughts on:

I am having a lot of trouble understanding the concepts of program behaviour and, as a visual person, am desperately trying to express exercise 3.4 as a diagram. Can anyone help with this.

I feel as though, without understanding how the objects and data are communicating, I will never be able to do much more than copy codes and hope for the best.

I'd like to be able to conceptualise all my programs in this diagram-like way. Am I making a mistake in thinking this way?

[Epicurus]

Would this be accurate?

[Epicurus]

This seems to be closer