Fixing animation snapback without setDisableActions:YES

gistfile1.m

// Implements the solution for solving "snapback" found in 
// Chapter 8 of "iOS Core Animation Advanced Techniques" by Nick Lockwood
// without the need to use setDisableActions: to override the implicit animation,
// instead passing in the implicit animation key in addAnimation:forKey:

// With setDisableActions
- (void)applyBasicAnimation:(CABasicAnimation *)animation toLayer:(CALayer *)layer
{
    //set the from value (using presentation layer if available)
    animation.fromValue = [layer.presentationLayer ?: layer valueForKeyPath:animation.keyPath];
    
    //update the property in advance
    //note: this approach will only work if toValue != nil 
    [CATransaction begin];
    [CATransaction setDisableActions:YES];
    [layer setValue:animation.toValue forKeyPath:animation.keyPath]; 
    [CATransaction commit];
    
    //apply animation to layer
    [layer addAnimation:animation forKey:nil]; 
}

// Without setDisableActions
- (void)applyBasicAnimation:(CABasicAnimation *)animation toLayer:(CALayer *)layer
{
    //set the from value (using presentation layer if available)
    animation.fromValue = [layer.presentationLayer ?: layer valueForKeyPath:animation.keyPath];
    
    // update the property in advance
    [layer setValue:animation.toValue forKeyPath:animation.keyPath]; 
    
    // Passing in the key overrides the implicit animation key for @"backgroundColor"
    [layer addAnimation:animation forKey:animation.keyPath]; 
}

- (IBAction)changeColor 
{
  //create a new random color
  CGFloat red = arc4random() / (CGFloat)INT_MAX; 
  CGFloat green = arc4random() / (CGFloat)INT_MAX; 
  CGFloat blue = arc4random() / (CGFloat)INT_MAX; 
  UIColor *color = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
  
  //create a basic animation
  CABasicAnimation *animation = [CABasicAnimation animation]; 
  animation.keyPath = @"backgroundColor";
  animation.toValue = (__bridge id)color.CGColor;
  
  //apply animation without snap-back
  [self applyBasicAnimation:animation toLayer:self.colorLayer]; 
}