If toValue equals the target's current value then completionBlock will fire immediately about pop HOT 1 OPEN

Two potential workarounds using the above code as an example:

A (best workaround)

Use animationDidStartBlock to set the target's value to match the fromValue. This will work even if the animation has a delayed beginTime. (If referencing self you may want to consider including [weak self] at the beginning of the block.)

flashAndFadeAnimation.animationDidStartBlock = { (animation) in
    view.alpha = flashAndFadeAnimation.fromValue as! CGFloat
}

B (simplest workaround if you aren't relying on beginTime)

Since POP actually changes the target's properties (unlike CAAnimation), you can set the target's property to the animation's fromValue before the animation is added:

view.alpha = flashAndFadeAnimation.fromValue as! CGFloat
view.pop_add(flashAndFadeAnimation, forKey: "flashAndFade")

C (quick, dirty, and error prone)

Set the toValue to something like 0.00001. But now if you then try to run this flash animation a second time the current value will now be the same as the toValue and the same problem can occur! To avoid this you might be able to set the target's value to 0.0 in the completionBlock.

from pop.