Increasing and Animating a Navigation Bar's height? - ios

Question

I subclassed UINavigationBar, and I have a button that drops down into a drop down menu. I wish to animate and push the contents below the navigation bar down as the navigation bar increases in height. Essentially I want a temporary table in the view of the navigationBar.
So far I overrode sizeThatFits() to return the custom sizes for the length I want, which is determined by a state enum. And I call sizeToFit() when the navigation bar needs to resize.
override func sizeThatFits(size: CGSize) -> CGSize {
let superSize = super.sizeThatFits(size)
var newSize: CGSize!
if(state == .Normal) {
newSize = CGSizeMake(superSize.width, superSize.height + heightIncrease)
} else if (state == .Menu) {
newSize = CGSizeMake(superSize.width, superSize.height + tableIncrease)
}
return newSize
}
func buttonPressed(){
if(state == .Normal){
state = .Menu
_delegate?.didChangeStateTo(.Menu)
} else if (state == .Menu){
state = .Normal
_delegate?.didChangeStateTo(.Normal)
}
UIView.animateWithDuration(0.3, animations: {
self.sizeToFit()
})
}
When I animate sizeToFit(), the navigation bar increases in size according to the animation, but the contents below the bar (the view of the viewController) immediately jumps down to the full length.
This is because sizeThatFits immediately returns the new CGSize. So the animation only works for the navigation bar itself, and the contents of the view do not follow the animation, but jump to their destination.
I tried avoiding using sizeThatFits, but UINavigationBar doesn't allow you to change the size of the bar simply by setting the frame with a CGRect.
I know there are other ways of going about this without playing around with subclassing UINavigationBar, but with my app's UI this way would be the most effective and code efficient.
Thanks in advance