Objective c 制作放大&；带UIScrollView的out视图

我正在尝试使用UIScrollView进行一些放大和缩小视图。 就像第一次点击使视图放大3倍，再点击一次使视图再次放大3倍，然后下一次点击将视图缩小回原始大小。 但是我的代码不能正常工作。 这个怎么了？ 谢谢

#导入“ViewController.h”
@界面视图控制器（）
@属性（强的，非原子的）IBMOutlet UIScrollView*myScrollView；
@属性（强，非原子）IBUIImageView*myImageView；
@结束
@实现视图控制器
-（无效）viewDidLoad
{
[超级视图下载]；
//加载视图后，通常从nib执行任何其他设置。
self.myScrollView.delegate=self；
self.myScrollView.minimumZoomScale=1；
self.myScrollView.maximumZoomScale=8；
self.myScrollView.scrollEnabled=是；
self.myScrollView.showshorizontalscrolindicator=YES；
self.myScrollView.showshorizontalscrolindicator=YES；
UITapGestureRecognizer*doubleTap手势=[[UITapGestureRecognizer alloc]initWithTarget:self-action:@selector（doubleTap:）]；
DoubleTapstore.numberOfTapsRequired=2；
self.myImageView.userInteractionEnabled=是；
[self.myImageView添加手势识别器：双击手势]；
}
-（无效）未收到记忆警告
{
[超级记忆警告]；
//处置所有可以重新创建的资源。
}
-（无效）双击：（UITapgestureRecognitor*）手势
{
if（self.myScrollView.zoomScale

#import "ViewController.h"

@interface ViewController ()

@property (strong, nonatomic) IBOutlet UIScrollView *myScrollView;
@property (strong, nonatomic) IBOutlet UIImageView *myImageView;


@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    self.myScrollView.delegate = self;

    self.myScrollView.minimumZoomScale = 1;
    self.myScrollView.maximumZoomScale = 8;

    self.myScrollView.scrollEnabled = YES;
    self.myScrollView.showsHorizontalScrollIndicator = YES;
    self.myScrollView.showsHorizontalScrollIndicator = YES;



    UITapGestureRecognizer  *doubleTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleTap:)];

    doubleTapGesture.numberOfTapsRequired = 2;
    self.myImageView.userInteractionEnabled = YES;
    [self.myImageView addGestureRecognizer:doubleTapGesture];




}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}



- (void)doubleTap:(UITapGestureRecognizer *)gesture
{

    if (self.myScrollView.zoomScale < self.myScrollView.maximumZoomScale){

        float newScale = self.myScrollView.zoomScale * 3;
        CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gesture locationInView:gesture.view]];

        [self.myScrollView zoomToRect:zoomRect animated:YES];

    }else{

        [self.myScrollView setZoomScale:1.0 animated:YES];
    }

}

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center
{
    CGRect zoomRect;
    zoomRect.size.height = [self.myScrollView frame].size.height * scale;
    zoomRect.size.width =  [self.myScrollView frame].size.width  * scale;

    zoomRect.origin.x = center.x - (zoomRect.size.width / 2.0);
    zoomRect.origin.y = center.y - (zoomRect.size.width / 2.0);

    return zoomRect;


}





#pragma mark - delegate

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.myImageView;
}



@end

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center
{
    CGRect zoomRect;
    zoomRect.size.height = [self.myScrollView frame].size.height / scale;
    zoomRect.size.width =  [self.myScrollView frame].size.width  / scale;

    zoomRect.origin.x = center.x - (zoomRect.size.width / 2.0);
    zoomRect.origin.y = center.y - (zoomRect.size.width / 2.0);

    return zoomRect;


}