swift animateWithDuration animation not right - ios

Question

I am hiding my navigation bar and a UIView under it that acts as a extension bar to it when I scroll my page.
My app is built like:
VC that holds a container view with an embedded table view.
From the table view I have delegates that notify VC1 once a user scrolls up or down.
My problem now is that the animation dont looks that good. What I am trying to do is to animate the extension bar to animate up or down with a fade in or fade out effect as well. When that occurs I also update the top contraint on my container view so that the table view will fill the whole screen. (I am not sure if I use layoutneeded() right or if something else should be used when updating constraints)
My code:
func ContainerTableViewControllerScrolledUp(controller: ContainerTableViewController) {
self.navigationController?.setNavigationBarHidden(false, animated: true)
println("UP")
UIView.animateWithDuration(
1.5,
delay: 0,
usingSpringWithDamping: 0.7,
initialSpringVelocity: 0.5,
options: nil,
animations: {
self.extensionV.alpha = 1
self.tableVConst.constant = 0
}, completion: { finished in
self.view.layoutIfNeeded()
}
)
}
func ContainerTableViewControllerScrolledDown(controller:ContainerTableViewController) {
self.navigationController?.setNavigationBarHidden(true, animated: true)
println("DOWN")
UIView.animateWithDuration(
1.5,
delay: 0,
usingSpringWithDamping: 0.7,
initialSpringVelocity: 0.5,
options: nil,
animations: {
self.extensionV.frame.origin.y = CGFloat(-10)
self.tableVConst.constant = -41
self.extensionV.alpha = 0
}, completion: { finished in
self.view.layoutIfNeeded()
}
)
}
extensionV is the extension view
tableVConst is the top constraint for my container view that holds my table view
So how should I edit my code in order to get the extension view to animate up/down with a fade in/fade out effect?

Answer 1

Instead of calling self.view.layoutIfNeeded() in the completion block, try calling it inside the animation block on the last line before it returns.