Objective C -> C

[Bruce Coughlin]

1) Is there a good book for C programmers to be able to read Objective C
code examples? I just want to know the basics for translation.

2) I'm trying to translate some code to C and am scratching my head a few
places. Here are the mysterious lines to me (not the entire function):

before the function:
- (IBAction) Install:(id)sender

inside the function:

NSBundle*myBundle = [NSBundle mainBundle];

NSString*path = [myBundle pathForResource:@"theDataFork" ofType:@"rsrc"];
NSURL *urlRef = [[NSURL alloc] initFileURLWithPath:path];


I have no idea what the line before the function means.
My guess on the first line inside the function:

CFBundleRef myBundle = CFBundleGetMainBundle();

for the next two, combine to one call:

CFURLRef urlRef =
CFBundleCopyResourceURL(myBundle,CFSTR("theDataFor k"),CFSTR("rsrc"),NULL);

though perhaps a CFURLCreate... function is correct, I don't know, but that
gets into CFAllocators.

Thanks for any insight.

-- Mac program, CW8 in C

[matt neuburg]

In <BB7A8FFF.ADE%brucecoughlin@nyc.rr.com> Bruce Coughlin wrote:

> 1) Is there a good book for C programmers to be able to read Objective
> C code examples?

An excellent book is on your computer. In fact, the book on Objective-C
on your computer is one of the best computer books I've ever read, on
any subject.

> I just want to know the basics for translation

There is no "translation". Objective-C is a C superset, not C in French.

> 2) I'm trying to translate some code to C and am scratching my head a
> few places

Because you don't know Objective-C. Learn it. It takes about an hour. m.

--
matt neuburg, phd = [email]matt@tidbits.com[/email], [url]http://www.tidbits.com/matt[/url]
REALbasic: The Definitive Guide! 2nd edition!
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[Paul Mitchum]

Bruce Coughlin <brucecoughlin@nyc.rr.com> wrote:

> 1) Is there a good book for C programmers to be able to read Objective C
> code examples? I just want to know the basics for translation.
>
> 2) I'm trying to translate some code to C and am scratching my head a few
> places. Here are the mysterious lines to me (not the entire function):
>
> before the function:
> - (IBAction) Install:(id)sender
>
> inside the function:
>
> NSBundle*myBundle = [NSBundle mainBundle];
>
> NSString*path = [myBundle pathForResource:@"theDataFork" ofType:@"rsrc"];
> NSURL *urlRef = [[NSURL alloc] initFileURLWithPath:path];
>
>
> I have no idea what the line before the function means.
> My guess on the first line inside the function:
>
> CFBundleRef myBundle = CFBundleGetMainBundle();
>
> for the next two, combine to one call:
>
> CFURLRef urlRef =
> CFBundleCopyResourceURL(myBundle,CFSTR("theDataFor k"),CFSTR("rsrc"),NULL);
>
> though perhaps a CFURLCreate... function is correct, I don't know, but that
> gets into CFAllocators.
>
> Thanks for any insight.
>
> -- Mac program, CW8 in C

Much of the Cocoa Foundation is 'toll-free bridged' with CoreFoundation
objects, so you're generally right to make the assumptions about
CFWhatever.

That said, you can install the Apple Developer Tools and compile
Objective-C/Cocoa programs. All for free, without translating it to
CoreFoundation.

My advice: Install the dev tools, learn enough Cocoa that you know an
IBAction and an id are, and then do the translation. You might find that
you've lost all momentum toward translating it to CoreFoundation, since
Cocoa does all the heavy lifting for you.

[brucecoughlin]

> My advice: Install the dev tools, learn enough Cocoa that you know an

> IBAction and an id are, and then do the translation. You might find that
> you've lost all momentum toward translating it to CoreFoundation, since
> Cocoa does all the heavy lifting for you.

Oooo you might be right, but this is a very small function in a much larger
(finished) C program. For future apps you're probably correct.

[David Phillip Oster]

In article <BB7A8FFF.ADE%brucecoughlin@nyc.rr.com>,
Bruce Coughlin <brucecoughlin@nyc.rr.com> wrote:

> 1) Is there a good book for C programmers to be able to read Objective C
> code examples? I just want to know the basics for translation.

I like the Hillegas book: "Cocoa Programming for Max OS X". "The Vermont
Recipes" are also good, and was available free online.
<http://www.stepwise.com/Articles/VermontRecipes/>

For free, you can get:
Inside Mac OS X: Object-Oriented Programming and the Objective-C
Language, Apple's Objective-C documentation
<http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC/ObjC.pdf>

It is probably already on your machine in
/Developer/Documentation/Cocoa/ObjectiveC/

> 2) I'm trying to translate some code to C and am scratching my head a few
> places. Here are the mysterious lines to me (not the entire function):
>
> before the function:
> - (IBAction) Install:(id)sender
> I have no idea what the line before the function means.

think:

extern IBAction Install(id sender);

and you won't be far wrong.

[Eric Pepke]

Bruce Coughlin <brucecoughlin@nyc.rr.com> wrote in message news:<BB7A8FFF.ADE%brucecoughlin@nyc.rr.com>...

> 1) Is there a good book for C programmers to be able to read Objective C
> code examples? I just want to know the basics for translation.

I second the recommendation for "The Objective C Programming Language"
on your computer.

However, your problem seems to be more converting between Cocoa and
Carbon, which is beyond the difference between Objectve C and C.
In many cases there isn't a 1-to-1 translation between Cocoa and Carbon,
though sometimes you can get close. Primarily, though, they're very
different beasts. The Cocoa objects, which are provided in Objective C
and Java, provide a lot of compact functionality which takes a lot more
lines in Carbon.

> before the function:
> - (IBAction) Install:(id)sender

This is the header; it's how Cocoa methods are declared. The minus sign
means it's an instance method, as opposed to a class method. If you
know C++, it corresponds roughly to

IBAction Foo::Install(id sender)

Except that IBAction, which is basically typedefed as void, also tells
the compiler that this can be linked as an action with a NIB file.

[Joe Davison]

On Tue, 02 Sep 2003, Bruce Coughlin wrote:

> 1) Is there a good book for C programmers to be able to read
> Objective C code examples? I just want to know the basics for
> translation.
>

Of course, as others have pointed out, the Objective-C manual that comes
with the developers tools is one place to start.

It might help to know that Objective-C ~=~ C + Smalltalk. That is, if
you understand both Smalltalk and C, you'll find individual statements
easy to read.

I don't know if there's an option on the compiler, but Objective-C is
(or used to be) translated into C as the first step in compilation -- so
if you can get the output of that pass, your job is done for you.

Of course, if you're doing the translation in order to port the code,
you've got a problem, as the Cocoa frameworks are probably most of the
code in most applications.

Otherwise, why translate it?

joe