Multiple UIView Animations - ios

Question

I have a UIButton that I have placed in the center of the screen using Interface Builder.
I want to animate the UIButton to move up and down and repeat the animation forever.
So far I have this in my didMoveToView:
UIView.animateWithDuration(3, animations: { () -> Void in
self.playBtn.transform = CGAffineTransformMakeTranslation(0, 10)
self.playBtn.transform = CGAffineTransformMakeTranslation(0, -10)
self.playBtn.transform = CGAffineTransformMakeTranslation(0, -10)
self.playBtn.transform = CGAffineTransformMakeTranslation(0, 10)
UIView.setAnimationRepeatCount(-1)
})
However it only runs the first line and moves the button down 10.

Answer 1

You can't change the transform to multiple things simultaneously. I would expect your code to cause no animation at all, as changing the transform more than once would cancel the animation.
Another problem with your code is that what you're saying is not how you ask for a repeating animation.
Still another problem is that you won't ever bring the button back to its starting place; the transforms are not additive.
What you need to do is chain animations together. This will be easiest if you drop down to Core Animation and make a grouped animation.
Or can do it with view animation by doing a keyframe animation, perhaps; this is not identical to what you want, but it will get you started:
Swift 2
let opts = UIViewKeyframeAnimationOptions.Repeat
UIView.animateKeyframesWithDuration(3, delay: 0, options: opts, animations: {
UIView.addKeyframeWithRelativeStartTime(0, relativeDuration: 0.5, animations: {
self.playBtn.transform = CGAffineTransformMakeTranslation(0, 10)
})
UIView.addKeyframeWithRelativeStartTime(0.5, relativeDuration: 0.5, animations: {
self.playBtn.transform = CGAffineTransformIdentity
})
}, completion: nil)
Swift 3,4,5
let opts = UIView.KeyframeAnimationOptions.repeat
UIView.animateKeyframes(withDuration: 3, delay: 0, options: opts, animations: {
UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5, animations: {
self.playBtn.transform = CGAffineTransform(translationX: 0, y: 10)
})
UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5, animations: {
self.playBtn.transform = CGAffineTransform.identity
})
}, completion: nil)
But really, it would be better if you learned how animation actually works before you get into this kind of thing. From your code, it appears to me you are just thrashing.