[marcowashere]

Hello... OK so last time I programmed for real was in C on Unix terminals in 1992... Now I'm trying to get into iPhone dev, and that involves...
- XCode environment
- Objective C

Both of which are hurting my brain.

I've decided to learn Objective-C and OO programming in general first, then move onto the frameworks and whatnot of the iPhone.

So I headed to the Objective-C Beginner's Guide at http://www.otierney.net/objective-c.html which is a nice intro, but I can't even get the first Classes example working (the Fractions class) :-(

I have a main.m, Fraction.h, and Fraction.m and I've scoured for syntax errors but in XCode it won't run.... instead i get these errors in the build results:
".objc_class_name_NSObject", referenced from:
.objc_class_name_Fraction in Fraction.o
"_objc_msgSend", referenced from:
_main in main.o
_main in main.o
_main in main.o
_main in main.o
_main in main.o
_main in main.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

I'm really really really new at this and obviously struggling with the very basics so have no idea where I'm going wrong.

I don't even know if I created the correct type of project in XCode, or the right type of file.

Can anyone please help point me in the right direction?

[Chuckit]

It sounds like you're not including Cocoa in the project. Did you make a Cocoa Application project (or a Cocoa Document-Based Application, or something else with "Cocoa" in the name)?

[CharlesS]

Sounds like you didn't link against the Foundation framework. Go to Project -> Add To Project... and then add /System/Library/Frameworks/Foundation.framework to the project. Then, your app should compile.

In the future, if you want to use Objective-C, you should start with Xcode's "Foundation Tool" template if you're making a command-line tool, or "Cocoa Application" or "Cocoa Document-based Application" if you're making a full-blown GUI app.

edit: beaten by the other Charles. However, since the only thing missing is NSObject, I'd guess he's trying to make a Foundation tool, and thus including just Foundation should work (but adding the entire Cocoa framework would work too).

[marcowashere]

Chuckit and CharlesS... You were both right...

I had created a new project based on the C++ Tool Template (d'Oh!), as the Objective-C Beginner's Guide didn't specify what to do here (it's IDE-neutral), so I took a stab at what I thought may be right LOL!

Thanks very much guys - adding the Foundation.framework fixed the problem.

I knew it would be simple for you fellas ;-)

[CharlesS]

BTW, if you want something that's more specifically tailored to Mac OS X, this book is supposed to be really good for learning Cocoa programming. I haven't read it myself, but I've often seen it heartily recommended by those who have.

[marcowashere]

Thanks for the advice... I already own that book and it's too advanced for my level ;-)

I'll get there eventually...

[Warhaven]

A friend of mine from Stanford pointed me to a series of great podcasts on iTunes-U provided for free by Stanford university. Search iTunes for "stanford cs-193p." It's an introductory course to development on the iPhone -- ObjC and Interface Builder. It assumes you have a basic understanding of OOP, like one semester of Java programming or something.

It's been really helpful to me, as I just started digging into ObjC last week.

-Rob