自定义UIButton无法与链接的UIImageView交互

我被以下代码困住了。 我的UIButton扩展类如何不能显示或隐藏UIImageView

正在调用我的方法,imageview不是nil。

代码如下:

@interface UILinkedImageButton : UIButton {
    IBOutlet UIImageView *linkImageView;
}

@property (nonatomic, retain) IBOutlet UIImageView *linkImageView;

@end

#import "UILinkedImageButton.h"

@interface UILinkedImageButton ()
- (void)showImage;
- (void)hideImage;
@end
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@implementation UILinkedImageButton


@synthesize linkImageView;

- (void) dealloc{

    [linkImageView release], linkImageView = nil;
    [super dealloc];
}

- (id) initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];

    if(self){
        [self addTarget:self action:@selector(showImage) forControlEvents:UIControlEventTouchDown];
        [self addTarget:self action:@selector(hideImage) forControlEvents:UIControlEventTouchUpInside];
        [self addTarget:self action:@selector(hideImage) forControlEvents:UIControlEventTouchUpOutside];
    }

    return self;
}

- (void)showImage
{
    if(self.imageView){
        NSLog(@"UILinkImageButton - showImage - currentStatus: %@", self.imageView);
        self.imageView.hidden = NO;
        [self.superview layoutIfNeeded];
    }   
}

- (void)hideImage
{
    if(self.imageView){
        NSLog(@"UILinkImageButton - hideImage");
        self.imageView.hidden = YES;
    }
}

@end