Obj-C, Constructors and Overloading

ConstructorsAndOverriding.m

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

+ (void) initialize {
  if (self == [Foo class]) {
    printf("Foo +initialize\n");
  }
}
 
- (id) init {
  self = [super init];
  if (self) {
    [self foo];
  }
  return self;
}
 
- (void) foo {
  printf("hello\n");
}
@end
 
@interface Bar : Foo
@end
 
@implementation Bar

+ (void) initialize {
  if (self == [Bar class]) {
    printf("Bar +initialize\n");
  }
}

- (id) init {
  self = [super init];
  if (self) {
    printf("Bar initializer\n");
    [self foo];
  }
  return self;
}
 
- (void) foo {
  printf("baa\n");
}
@end
 
int main( int argc, const char *argv[] ) {
    id foo = [[Bar alloc] init];
    return 0;
}

output.txt

Foo +initialize
Bar +initialize
baa
Bar initializer
baa

Oops, + (void) initialize is only for class-level initialization, so might not be at all useful here.