UIView is not aminating for the first time

Question

I am trying to animate a UIView on button click. It does appear on first click but only after that.

@IBAction func viewDetails(sender: AnyObject) {

     UIView.animateWithDuration(0.5 as NSTimeInterval, animations: {
                   println(self.viewDetailsView.center.x)
                    println(self.viewDetailsView.hidden)
                    self.viewDetailsView.hidden = false
                    self.viewDetailsView.center = CGPointMake(self.viewDetailsView.center.x - 4000, self.viewDetailsView.center.y)
                    self.view.layoutIfNeeded()
                    }, completion: {
                        finished in
                        self.detailsVisible = true
                }) }

Answer 1

Trying this:

@IBAction func viewDetails(sender: AnyObject) {

    println(self.viewDetailsView.center.x)
    println(self.viewDetailsView.hidden)
    self.viewDetailsView.hidden = false
    self.viewDetailsView.center = CGPointMake(self.viewDetailsView.center.x - 4000, self.viewDetailsView.center.y)

    UIView.animateWithDuration(0.5 as NSTimeInterval, animations: {

        self.view.layoutIfNeeded()
    }, completion: { finished in
        self.detailsVisible = true
    }) 
}