Understanding where auto constraints are being set - ios

Question

In the below autolayout challenge 6, from Ray W, I can't understand where in the code, the width and height change after it is tapped more than once.
It is set to 50 in IB, and on the first run through within the tappedImage method, in the last else condition, width.constant = 100, but when does this ever get redefined back to 50 (width.constant = 50)?!?
AND, after the first tap (i.e., width and height of this image = 100), tapping another image next, the width and height of the first image goes back to 50 while the second image grows to 100. Where in the last else condition does it tell the first image to resize to 50?
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var rayWidth: NSLayoutConstraint!
#IBOutlet weak var rayHeight: NSLayoutConstraint!
#IBOutlet weak var ray: UIImageView!
#IBOutlet weak var vickiWidth: NSLayoutConstraint!
#IBOutlet weak var vickiHeight: NSLayoutConstraint!
#IBOutlet weak var vicki: UIImageView!
#IBOutlet weak var gregWidth: NSLayoutConstraint!
#IBOutlet weak var gregHeight: NSLayoutConstraint!
#IBOutlet weak var greg: UIImageView!
#IBOutlet weak var micWidth: NSLayoutConstraint!
#IBOutlet weak var micHeight: NSLayoutConstraint!
#IBOutlet weak var mic: UIImageView!
#IBOutlet weak var christineWidth: NSLayoutConstraint!
#IBOutlet weak var christineHeight: NSLayoutConstraint!
#IBOutlet weak var christine: UIImageView!
#IBOutlet weak var name: UILabel!
#IBOutlet weak var bio: UITextView!
var heights:[NSLayoutConstraint]!
var widths:[NSLayoutConstraint]!
var bios: [String]!
var names: [String]!
#IBOutlet weak var emailButton: UIButton!
var previousHeight: NSLayoutConstraint?
var previousWidth: NSLayoutConstraint?
override func viewWillAppear(animated: Bool) {
bios = ["Ray is an indie software developer currently focusing on iPhone and iPad development, and the administrator of this site. He’s the founder of a small iPhone development studio called Razeware, and is passionate both about making apps and teaching others the techniques to make them.", "Vicki Wenderlich discovered a love of digital art in 2009, and has been making app art and digital illustrations ever since. She is passionate about helping people pursue their dreams, and makes free app art for developers available on her website, http://www.vickiwenderlich.com.", "Greg is an iOS developer and trainer, and has been on the raywenderlich.com editorial team since 2012. He has been nerding out with computers since the Commodore 64 era in the 80s and continues to this day on the web and on iOS. He likes caffeine, codes with two-space tabs, and writes with semicolons.", "Mic Pringle is a developer, editor, podcaster, and video tutorial maker. He's also Razeware's third full-time employee. When not knee-deep in Swift or stood in-front of his green screen, he enjoys spending time with his wife Lucy and their daughter Evie, as-well as attending the football matches of his beloved Fulham FC. You can find Mic on Twitter, GitHub, and Stack Overflow.", "Christine is Ray's administrative assistant. She tries to keep order in the ever expanding world of raywenderlich.com so that Ray and the team can stay focused on making more tutorials, books, and apps!"]
names = ["Ray Wenderlich", "Vicki Wenderlich", "Greg Heo", "Mic Pringle", "Christine Sweigart"]
name.text = ""
emailButton.hidden = true
}
override func viewDidLoad() {
super.viewDidLoad()
var razeware = [ray, vicki, greg, mic, christine]
heights = [rayHeight, vickiHeight, gregHeight,micHeight,christineHeight]
widths = [rayWidth, vickiWidth, gregWidth,micWidth,christineWidth]
for image in razeware {
var tapGesture = UITapGestureRecognizer(target: self, action: "tappedImage:")
image.userInteractionEnabled = true
image.addGestureRecognizer(tapGesture)
}
}
func tappedImage(sender:UITapGestureRecognizer!) {
var tag = 0
// index / tag who's been tapped
if let senderTag = sender.view?.tag {
tag = senderTag
}
let width = widths[tag] // get the width constraint from the array
let height = heights[tag]
print(width)
view.setNeedsUpdateConstraints()
if previousHeight == height {
if previousHeight?.constant == 100 {
previousHeight?.constant = 50
previousWidth?.constant = 50
print("through here")
//UIView.animateWithDuration(3.0, animations: { () -> Void in
self.name.text = ""
self.bio.text = ""
self.emailButton.hidden = true
// self.view.layoutIfNeeded()
// })
} else {
previousHeight?.constant = 100
previousWidth?.constant = 100
print("Going here")
name.text = names[tag]
bio.text = bios[tag]
bio.font = UIFont.systemFontOfSize(15.0)
bio.textColor = UIColor.whiteColor()
emailButton.hidden = false
}
} else {
previousHeight?.constant = 50
previousWidth?.constant = 50
UIView.animateWithDuration(5.0, animations: { () -> Void in
width.constant = 100
height.constant = 100
self.name.text = self.names[tag]
self.bio.text = self.bios[tag]
self.bio.font = UIFont.systemFontOfSize(15.0)
self.bio.textColor = UIColor.whiteColor()
self.emailButton.hidden = false
self.view.layoutIfNeeded()
})
}
print(width)
previousHeight = height
previousWidth = width
print("Previous: \(previousHeight)")
print("Height: \(height)")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

Even if a constraint was re-defined in code elsewhere previously, layoutIfNeeded() will revert to the original IB defined constraint value - unless the constraint is re-defined again (to maintain its new value) after setNeedsUpdateContraints().
This is based on a lot of trial an even more error. Perhaps there is still a chance for a better answer...