subclassing.m

#import <Foundation/Foundation.h>


/*
  $ gcc -x objective-c -Wno-import -lobjc -framework Foundation subclassing.m
  $ ./a.out
  -[FooThatCallsSelf initWithBar:]
  -[SubFooThatCallsSelf init]
  -[FooThatCallsSuper initWithBar:]
*/


@interface FooThatCallsSelf : NSObject
@end

@implementation FooThatCallsSelf
- (id)initWithBar:(NSString *)bar {
  printf("-[FooThatCallsSelf initWithBar:]\n");
  return [self init];
}
@end


@interface SubFooThatCallsSelf : FooThatCallsSelf
@end

@implementation SubFooThatCallsSelf
- (id)init {
  printf("-[SubFooThatCallsSelf init]\n");
  return [super init];
}
@end


@interface FooThatCallsSuper : NSObject
@end

@implementation FooThatCallsSuper
- (id)initWithBar:(NSString *)bar {
  printf("-[FooThatCallsSuper initWithBar:]\n");
  return [super init]; // this is incorrect
}
@end


@interface SubFooThatCallsSuper : FooThatCallsSuper
@end

@implementation SubFooThatCallsSuper
- (id)init {
  printf("-[SubFooThatCallsSuper init]\n"); // will not be printed
  return [super init];
}
@end


int main(void) {
  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
  
  [[[SubFooThatCallsSelf alloc] initWithBar:@"BAR!"] autorelease];
  [[[SubFooThatCallsSuper alloc] initWithBar:@"BAR!"] autorelease];
  
  [pool release];
}