NSLayoutConstraints crashing on ios7 but not on ios8 - ios7

Question

I've setup in a UIViewController some layout constraints which works fine on ios8. But as soon as I run it on ios7 i've got the following error :
*** Assertion failure in -[UIView layoutSublayersOfLayer:], /SourceCache/UIKit_Sim/UIKit-2935.137/UIView.m:8803
Here is my code :
class DatacenterIndicatorViewController: UIViewController {
let sideMargins:Float = 12.0
var dataCenterPollingLabel:UILabel = UILabel()
var dataCenterAlarmLabel:UILabel = UILabel()
//MARK: - Life cycle
override func viewDidLoad() {
super.viewDidLoad()
self.view.addSubview(dataCenterPollingLabel)
self.view.addSubview(dataCenterAlarmLabel)
}
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
self.reloadData()
}
func reloadData() {
self.setupAlarmLabel()
self.setupPollingLabel()
self.generateConstraints()
}
func setupPollingLabel() {
// some graphic setup
}
func setupAlarmLabel() {
// some graphic setup
}
func generateConstraints() {
self.dataCenterPollingLabel.setTranslatesAutoresizingMaskIntoConstraints(false)
self.dataCenterAlarmLabel.setTranslatesAutoresizingMaskIntoConstraints(false)
self.view.addConstraint(NSLayoutConstraint(item: dataCenterPollingLabel, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1.0, constant: 0.0))
self.view.addConstraint(NSLayoutConstraint(item: dataCenterAlarmLabel, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1.0, constant: 0.0))
self.view.addConstraint(NSLayoutConstraint(item: dataCenterAlarmLabel, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: dataCenterPollingLabel, attribute: NSLayoutAttribute.Width, multiplier: 1.0, constant: 0.0))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat(NSString(format:"H:|-==%f-[dataCenterPollingLabel]-==%f-[dataCenterAlarmLabel]-==%f-|", sideMargins, sideMargins, sideMargins), options: NSLayoutFormatOptions.allZeros, metrics: nil, views: ["dataCenterPollingLabel": dataCenterPollingLabel, "dataCenterAlarmLabel": dataCenterAlarmLabel]))
}
}
What is wrong in my code ? I can even know where to look for some errors, everything looks fine to me.

Answer 1

I faced the same issue in iOS 7 version. Calling self.view.layoutIfNeeded() function instead of super.viewDidLayoutSubviews() function at the end of the viewDidLayoutSubviews method solved the issue.
Code snippet
override func viewDidLayoutSubviews() {
// Your statements
self.reloadData()
//Write the below statement at the end of the function
self.view.layoutIfNeeded()
}