Compiling simple Objective-C programs using a Makefile

While writing my "Objective-C for Java Programmers" guide, I found that I needed a way to write short snippets of Objective-C code without creating a whole new project in Xcode.

Coming from a server hacker's point of view, I thought, what better way to do this than to do everything from the command line. And if I was going to do this for all my examples, I might as well create a reusable makefile for this!

Below, we have a setup with a makefile, a main file, and a objective-c header and implementation source file. The makefile will compile objective-c modules and link them with the main source file to create a "hello" executable.

The makefile:

CC = clang

MAIN = hello

SRCS = main.o Test.o

default: $(MAIN)

$(MAIN): $(SRCS)
 $(CC) -O0 -Wall -o $(MAIN) $(SRCS) -framework Foundation

clean:
 find . -name "*.o" -exec rm {} \;
 if [ -f "$(MAIN)" ]; then rm $(MAIN); fi

all: default

Test.h

#import <Foundation/NSObject.h>

@interface Contrived : NSObject
{
}
- (void)log:(NSString *)arg1;
@end

Test.m

#import "Test.h"
#import <Foundation/Foundation.h>

@implementation Contrived
- (void)log:(NSString *)arg1
{
    NSLog(@"From Contrived.log: %@", arg1);
}
@end

main.m

#import "Test.h"
#import <Foundation/Foundation.h>
                                                                                                                                                                     
int main (void)                                                                                                                                                      
{                                                                                                                                                                    
    NSAutoreleasePool *pool = [NSAutoreleasePool new];
                                                                                                                                                                     
    id simpleObj = [Contrived alloc];
    [simpleObj log:@"Hello World!"];
                                                                                                                                                                     
    [simpleObj release];
    [pool release];
    return 0;
}

A couple of notes about the makefile:

CC=clang

This specify the compiler/linker. You can specify alternatives such as gcc. But Clang generally provides cleaner error messages which is important for working on test snippets.

SRCS = main.o Test.o

This allows you to specify additional modules to compile (other than the main function) here, separated by a single space. For example, if you want to another module with the files "MyLibrary.h" and "MyLibrary.m", then your SRCS declaration would be:

SRCS = main.o Test.o MyLibrary.o

That's it. Get coding!