not sure yet...

gistfile1.txt

@implementation TopViewController

- (void)viewDidLoad{
    [super viewDidLoad];
    
    if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7) {
        
        NSDictionary *views = @{@"topGuide": self.topLayoutGuide, @"mainView": self.view};
        
        [self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[topGuide]-20-[mainView]"
                                                                          options:kNilOptions
                                                                          metrics:nil
                                                                            views:views]]; 
    }
    
    
}