how to master Cocoa & Objective-C

It’s been quiet on Applehelpwriter this month, largely because we’re all waiting for OS X Mavericks to come out, and I’ve been rather busy helping out with the beta testing. I’ll have plenty to tell you when the public release finally comes around, but for now I’m under strict orders from Apple’s NDA (Non-Disclosure Agreement) to keep schtumm.

Xcode 5 was released for Mountain Lion last week, and that brought up a couple of questions about how to develop competency in creating apps for Mac OS X. I wrote something about this sometime ago, but the truth is I’ve been through a bit of a learning curve myself since then. So, while we wait for Mavs (10.9) and explore the new features of Xcode 5, this seems like the perfect time to share some of my coding experience. Although this might seem a little diaristic, the aim of this post – like pretty much all others on APH – is purely tutorial. 🙂

So, let me go back about a year or so. I’d been working my way through the 4th edition of Aaron Hillegass and Adam Preeble’s widely-acclaimed ‘Cocoa Programming for Mac OS X‘ quite nicely till I hit the ‘challenge’ at the end of Chapter 5. Although I’d followed all the previous chapters quite carefully and with little trouble, the challenge seemed totally beyond me. Indeed, as I read and re-read the earlier material, I couldn’t see anything in the book that would help me solve the core problem of the challenge.

The challenge said: “when the user types in a string and clicks the button, change the message text to display the input string and the number of characters“.

Building the interface was easy, but at that time I had no idea how to go about measuring the string length (despite the mention offered on the next page about the -(NSUInteger) length method.)

After struggling with the problem for some while and not being able to resolve it, I came to an impasse: either I moved on to the next chapter, hoping that I’d learn more and be able to solve this challenge at a later date, or I gave up on the book completely. I wrestled with this for a while, until eventually deciding that I needed to postpone going any further into the book ( a different strategy from ‘giving up’!), and instead learn more about the underlying programming language behind Cocoa, namely Objective-C.

I should point out at this point that the authors are quite clear at the beginning that you really should know your way around Objective-C before tackling Cocoa, but since the early chapters – and even the chapter that reviews Objective-C itself – are fairly light, I fell into the mistake of thinking that I could get by with what they provided, a little background knowledge, and some judicious internet browsing to fill in the gaps.

Alas, that was far from the truth. I put aside the Hillegass book and turned instead to Stephen Kochan’s primer on Objective C, the excellent ‘Programming in Objective-C 2.0‘. In fact, I’d already read a couple of chapters of this in the past, (that’s the “little background knowledge” I mentioned in the last paragraph), but it was clear that I needed to work through it in far more detail if I hoped to master Cocoa.

Kochan begins his book by saying you don’t need to know C to read it, and indeed it’s true (in retrospect…) that he does a good job of surreptitiously teaching your the heart of the C programming language under the guise of teaching you Objective-C. When I say “surreptitious” that’s not a criticism: Objective-C is an extension of the C programming language, and in fact it isn’t really that much different from it once you re-orient your idea of what a program is and how it works. It’s kind of like those black and white gestalt pictures in psychology ( you know, “do you see a rabbit or an old lady”?). Once you switch your perspective, it becomes fairly clear, but until then though, the other point of view can seem as obscure as mud.

Well, I got through about six or seven chapters of Kochan and again got stumped. It occurred to me then that despite his claim that you didn’t need C to learn Objective-C, I…well…needed to learn C before I could learn Objective-C!

So I embarked on a mission to first learn C, which I did through a couple of excellent books: first, with Dave Mark’s ‘Learn C on the Mac‘ and then with the classic ‘The C Programming Language‘ by Kernighan and Ritchie (K&C). If you have trouble finding a reasonably priced version of this venerable book in hardcopy, do as I did and try your local public or university library, both of which are sure to have it. In my earlier post, I also suggested you look at ‘C for Dummies‘ (another book I was reading concurrently with my first attempt at Kochan back then), but in retrospect, that book doesn’t cover enough ground and takes too long to cover what it does deal with, so I think now I’d say give that one a miss.

In any case, six months after working my way through the Dave Mark and the K&C books, I approached Kochan again, and found myself working through it like a hot knife through butter. After that, I finally went back to Hillegaas. And guess what? Not only did that challenge at the end of Chapter 5 seem trivial in Objective-C, I actually knew how to solve it even more efficiently in C without even using Objective-C at all!

(Even more efficiently? Well, only to computer programmers, who count spaces as ‘characters’, does the string “This is only a test” have 19 characters. To normal people, it’s only got 15. An early lesson in K&C will teach you how to count the characters without including any white space. 😉 ).

Now I said this would be a tutorial, and indeed it is, for the moral of the story is an old one: learn to walk before you run. Do not believe the many claims that are often touted that you can learn how to create great apps for Mac OS X (or iOS) just by reading a book or two on Xcode or Cocoa (or anything else). Instead, get your foundations sorted out before you start trying to tackle Cocoa or even Objective-C.

And that means: learn C, the ‘grandfather’ of all modern OOP languages, which will not only make the rest of the learning curve a relatively easy glide, but will equip you with a far deeper understanding of what you’re doing and a far greater ability to tackle harder problems. You’ll learn how to create more complex apps than you ever could have with just a superficial knowledge of the ‘higher-level’ languages. Like the tortoise and the hare, it might seem like you’re the slow coach at first, but before you get to the end of the track, you’ll find you’re leagues ahead of the competition. 🙂

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