Blink Animation

ViewController.m

//
//  ViewController.m
//  Animation
//

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *image;
@property (strong, nonatomic) IBOutlet UILabel *label;
@property (strong, nonatomic) IBOutlet UILabel *label2;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self performSelector:@selector(animateView) withObject:nil afterDelay:2];
}

- (void) animateView {
    [UIView animateWithDuration:1.0
                     animations:^{
                         self.label.alpha = 0;
                     }
                     completion:^(BOOL finished) {
                         [self animateView2];
                     }];
}

- (void) animateView2 {
     [UIView animateWithDuration:1.0
                     animations:^{
                         self.label2.alpha = 1.0;
                     }
                     completion:^(BOOL finished) {
                         [self animateView3];
                     }];
}

- (void)animateView3 {
    [UIView animateWithDuration:1.0
                     animations:^{
                         self.label2.alpha = 0.0;
                     }
                     completion:^(BOOL finished) {
                         [self animateView4];
                     }];
}

- (void)animateView4 {
    [UIView animateWithDuration:1.0
                     animations:^{
                         self.label.alpha = 1;
                     }
                     completion:^(BOOL finished) {
                         [self animateView];
                     }];
}

@end

Should use recursion here