GNUstep quick start on Linux

I'm enjoying tinkering with Cocoa on my Leopard Mac and I thought it might be fun to take a peek at Objective C and the framework on Linux in particular for developing command line tools.

My thinking is that it would be nice to develop the code under XCode and then just compile for Linux if I can figure out where the frameworks diverge and keep to compatible code.

Here's a quick start guide for Fedora Core 5 assuming that you already have the basic gcc (I'm sure it's basically the same on others):

• sudo yum install gcc-objc
• wget ftp://ftp.gnustep.org/pub/gnustep/core/gnustep-startup-0.18.2.tar.gz
• tar xzf gnustep-startup-0.18.2.tar.gz
• cd gnustep-startup-0.18.2
• sudo ./InstallGNUstep
• Edit your ~/.bash_profile to add the line . /usr/GNUstep/System/Library/Makefiles/GNUstep.sh
• (note the leading dot in the line above)

Here is a little test program, called first.m:

#import <foundation/foundation.h>

int main(int argc, char** argv, char** env)
{
NSLog(@"Hello");
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

NSMutableArray * array = [NSMutableArray new];
[array addObject: [NSString stringWithString:@"one"]];
[array addObject:[NSString stringWithString:@"two"]];
[array addObject:[NSString stringWithString:@"three"]];
[array addObject:[NSString stringWithString:@"four"]];
[array addObject:[NSString stringWithString:@"five"]];
[array addObject: @"six"];

NSEnumerator * e = [array objectEnumerator];
NSString * string;
while ((string = [e nextObject]))
{
NSLog(string);
}
[pool release];
return 0;
}

Create a file called GNUmakefile:

include $(GNUSTEP_MAKEFILES)/common.make
TOOL_NAME = first
first_OBJC_FILES = first.m
include $(GNUSTEP_MAKEFILES)/tool.make

Then make and run:

[marksp@homelinux first]$ make
Making all for tool first...
Compiling file first.m ...
Linking tool first ...
[marksp@homelinux first]$ obj/first
2007-11-04 04:38:40.246 first[1257] Hello
2007-11-04 04:38:40.276 first[1257] one
2007-11-04 04:38:40.277 first[1257] two
2007-11-04 04:38:40.278 first[1257] three
2007-11-04 04:38:40.278 first[1257] four
2007-11-04 04:38:40.279 first[1257] five
2007-11-04 04:38:40.279 first[1257] six

The same code can be built in Xcode and will run on the mac.

The GNUstep framework is very well documented here. 

One immediate incompatibility I ran into was the starter code for a Foundation command line tool ended with [pool drain] instead of [pool release] - a little DTS humour no doubt!