从viewDidLoad调用方法时，CABasicAnimation不起作用

我有一个imageView添加到一个显示为modalViewController的视图中，具有水平翻转样式. 我添加了以下代码来为imageView设置动画.

I have an imageView added to a view that's presented as a modalViewController, with style horizontal flip. I have added the following code for animating the imageView.

- (void)animateTheImageview:(UIImageView*) imageViewToAnimate{
    
    CABasicAnimation *fadeAnimation;
    fadeAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
    fadeAnimation.duration = 1.5;
    fadeAnimation.repeatCount = INFINITY;
    fadeAnimation.autoreverses = NO;
    fadeAnimation.fromValue = [NSNumber numberWithFloat:1.0];
    fadeAnimation.toValue = [NSNumber numberWithFloat:0.5];
    fadeAnimation.removedOnCompletion = YES;
    fadeAnimation.fillMode = kCAFillModeForwards;
    [imageViewToAnimate.layer addAnimation:fadeAnimation forKey:@"animateOpacity"]; 
}


- (void)switchOnorOff
 {
    
    if (onOffSwitch.on)
    {
        
        self.lightImage.image = [UIImage imageNamed:@"CFLGlow.jpg"];
        [self animateTheImageview:self.lightImage];
    }
    else
    {
        
        self.lightImage.image = [UIImage imageNamed:@"CFL-BULB.jpg"];
        [self.lightImage.layer removeAllAnimations];
    }
}

我正在从viewDidLoad调用此方法:

- (void)viewDidLoad
   {
      [self switchOnorOff];
   }

我的问题是上面的代码没有为imageView设置动画.

My issue is the above code doesn't animate the imageView.

但是当我尝试下面的代码时，它会起作用:

But when I tried the below code it works:

[self performSelectorOnMainThread:@selector(animateTheImageview:) withObject:self.lightImage waitUntilDone:YES];

我的问题是为什么会发生此问题? 两者之间有什么区别吗?

My question is why this issue is happening ? Is there any difference between,

[self performSelectorOnMainThread:@selector(animateTheImageview:) withObject:self.lightImage waitUntilDone:YES];

和

[self animateTheImageview:self.lightImage];