UIView height constraint animation, which has anchor connection with other views - xcode

Question

Xcode swift 4
I have some views that are added dynamically in code one below another.
Each new view top anchor is connected to previous view bottom anchor.
And each view have a button that make view to expand/collapse with animation. Here is button code :
let fullHeight : CGFloat = 240
let smallHeight : CGFloat = 44
let currentHeigth = rootView.frame.size.height //I use this to get current height and understand expanded view or not
let heighCons = rootView.constraints.filter //I use this to deactivate current height Anchor constraint
{
$0.firstAttribute == NSLayoutAttribute.height
}
NSLayoutConstraint.deactivate(heighCons)
rootView.layoutIfNeeded()
if currentHeigth == smallHeight
{
rootView.heightAnchor.constraint(equalToConstant: fullHeight).isActive = true
rootView.setNeedsLayout()
UIView.animate(withDuration: 0.5)
{
rootView.layoutIfNeeded() //animation itself
}
}
else
{
rootView.heightAnchor.constraint(equalToConstant: smallHeight).isActive = true
rootView.setNeedsLayout()
UIView.animate(withDuration: 0.5)
{
rootView.layoutIfNeeded() //animation itself
}
}
This all works perfectly but i have a problem : view that below current expanding view changes it y position immediately with no animation. Its just jumping to previous view bottom anchor, that would be active after animation finish.
So my question is :
1) what is the right way to make height constraint animation, when views are connected to each other by bottom/top animation?
2) my goal is just to make a view that would expand/collapse on button click, maybe i should do it another way?

Answer 1

Here's an approach using Visiblity Gone Extension
extension UIView {
func visiblity(gone: Bool, dimension: CGFloat = 0.0, attribute: NSLayoutAttribute = .height) -> Void {
if let constraint = (self.constraints.filter{$0.firstAttribute == attribute}.first) {
constraint.constant = gone ? 0.0 : dimension
self.layoutIfNeeded()
self.isHidden = gone
}
}
}
Usage
expanview.visiblity(gone: true,dimension: 0)
Example
#IBOutlet weak var msgLabel: UILabel!
#IBOutlet weak var expanview: UIView!
#IBAction func toggleCollapisbleView(_ sender: UIButton) {
if sender.isSelected{
sender.isSelected = false
expanview.visiblity(gone: false,dimension: 128)
sender.setTitle("Collapse",for: .normal)
}
else{
sender.isSelected = true
expanview.visiblity(gone: true,dimension: 0)
sender.setTitle("Expand",for: .normal)
msgLabel.text = "Visiblity gone"
}
}