ctors.m

//
//  AppDelegate.m
//  simpletestapp
//
//  Created by Rolf Bjarne Kvinge on 13/04/15.
//  Copyright (c) 2015 Rolf Bjarne Kvinge. All rights reserved.
//

#import "AppDelegate.h"

@interface A : NSObject
-(instancetype) init;
-(instancetype) initToday;
@end

@interface B : A
-(instancetype) init;
-(instancetype) initToday;
@end

@implementation A
-(instancetype) init
{
    NSLog (@"A init");
    return [super init];
}
-(instancetype) initToday
{
    NSLog (@"A initToday");
    return [self init];
}
@end

@implementation B
-(instancetype) init
{
    NSLog (@"B init");
    return [super init];
}
-(instancetype) initToday
{
    NSLog (@"B initToday");
    return [super initToday];
}
@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    NSLog (@"Test 1");
    [[B alloc] init];
    NSLog (@"Test 1 done");
    NSLog (@"Test 2");
    [[B alloc] initToday];
    NSLog (@"Test 2 done");
    return YES;
}

@end

output

Test 1
B init
A init
Test 1 done
Test 2
B initToday
A initToday
B init
A init
Test 2 done