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Why is this object being prematurely deallocated under ARC?
//  TestViewController.m
@implementation TestViewController

@synthesize scrollContentView

- (void)viewDidLoad
{
    [super viewDidLoad];
 SecondViewController *secondViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"SecondViewController"];

[self.scrollContentView addSubview:secondViewController.view];
}

@end

// SecondViewController.m
- (void)viewDidLoad
{
    [super viewDidLoad];
    UIButton *button1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [button1 addTarget:self action:@selector(button1Click:) forControlEvents:UIControlEventTouchUpInside];
    button1.frame = CGRectMake(20, 45, 280, 40);
    [self.view addSubview:button1];
}

- (IBAction)button1Click:(id)sender
{
    NSLog(@"test");
}

@implementation TestViewController{
    SecondViewController *secondViewController; // with ARC ivars are strong by default
}

secondViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"SecondViewController"];

- (void)addChildViewController:(UIViewController *)childController __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_5_0);