UISwitch - detecting end of animation

Question

I have an UISwitch which is inside of a UITableViewCell. I have a target action assigned to switch:

[switch addTarget:self action:@selector(changeSwitchColor:) forControlEvents:UIControlEventValueChanged];

- (void)changeSwitchColor:(id)sender
{
    ...
}

The problem is that the changeSwitchColor: is called before the animation is finished, yet I want to detect when animation has finished, so I can set the thumbTintColor property without breaking the animation.

My attempt to detect the animation by using UIView setAnimationDidStopSelector: method:

[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context
{
    ...
}

But this method is not called on UISwitch finishing the animation (I'm not even sure how the animation is made internally).

How could I detect the finishing state of UISwitch?

Thanks!

Answer 1

You can use CATransaction.setCompletionBlock(_:).

addTarget(self, action: #selector(valueChanged(sender:)), for: [.valueChanged])

@objc private func valueChanged(sender: UISwitch) {
    CATransaction.setCompletionBlock { [onChange] in
        onChange?(sender.isOn)
    }
}

The documentation says the block is guaranteed to be called even if there are no animations or the animation was removed. It makes it very safe to use.