ObjC Using Categories to Modularise Long File

foo+foobar.h

#import "foo.h"

@interface Foo (foobar)

- (void) foo;
- (void) bar;

@end

foo+spamegg.h

#import "foo.h"

@interface Foo (spameggs)

- (void) spam;
- (void) eggs;

@end

foo.h

#import <stdio.h>
#import <Foundation/Foundation.h>
 
@interface Foo : NSObject
- (void)foo;
- (void)bar;
- (void)spam;
- (void)eggs;
@end

longfoo.m

#import "foo.h"

@implementation Foo

- (void) foo {
  printf("foo\n");
}

- (void) bar {
  printf("bar\n");
}

- (void) spam {
  printf("spam\n");
}

- (void) eggs {
  printf("eggs\n");
}

@end

main.m

#import <stdio.h>
#import "foo.h"

int main(int argc, char **argv) {
  Foo *f = [Foo new];

  [f foo];
  [f bar];
  [f spam];
  [f eggs];

  return 0;
}

shortfoo+foobar.m

#import "foo.h"

@implementation Foo (foobar)

- (void) foo {
  printf("foo\n");
}

- (void) bar {
  printf("bar\n");
}

@end

shortfoo+spameggs.m

#import "foo.h"

@implementation Foo (spameggs)

- (void) spam {
  printf("spam\n");
}

- (void) eggs {
  printf("eggs\n");
}

@end

shortfoo.m

#import "foo.h"
#import "foo+foobar.h"
#import "foo+spameggs.h"

@implementation Foo
@end

To compile with the "long" file, of course:

gcc -lobjc longfoo.m main.m -o longfoo.out

To compile with the "short" files:

gcc -lobjc shortfoo.m shortfoo+foobar.m shortfoo+spameggs.m main.m -o shortfoo.out

With the latter, however, since shortfoo.m is an incomplete implementation (we leave methods to categories), and because some methods of the primary class are implemented by categories, we get two warnings for each method: incomplete-implementation and objc-protocol-method-implementation.