IOS bug constraints ViewDidAppear vs ViewDidLoad - ios

Question

I work since 2 days on this problem without understanding the mindfuck behind it...
So to explain quickly, I create a view based on a Nib in an other storyboard like this:
let storyboard = UIStoryboard(name: "TestNib", bundle: nil)
testNib = storyboard.instantiateViewControllerWithIdentifier("TestNib") as! TestNib
testNib.view.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(testNib.view)
and I add some constraints manually with constraintsWithVisualFormat like this:
constraint_V = NSLayoutConstraint.constraintsWithVisualFormat(
"V:|-(10)-[conversationMenu(300)]",
options: NSLayoutFormatOptions(rawValue: 0),
metrics: nil, views: ["conversationMenu": testNib.view])
let constraint_H = NSLayoutConstraint.constraintsWithVisualFormat(
"H:|[conversationMenu]|",
options: NSLayoutFormatOptions(rawValue: 0),
metrics: nil, views: ["conversationMenu": testNib.view])
self.view.addConstraints(constraint_V)
self.view.addConstraints(constraint_H)
No problem, everything work super fine. (I also try with a view in the storyboard by the way).
The main problem is when I want to animate this view, the constraints into "testNib" (self.view.addSubview(testNib.view)) break. And this happened when I create the constraintsWithVisualFormat in the ViewDidAppear. In the ViewDidLoad everything work perfectly...
This are my instances' variables:
var testNib: TestNib!
var constraint_V: [NSLayoutConstraint]!
var completion = false
And this is my code to animate the constraints:
if completion == false {
for constraint in constraint_V {
if constraint.firstAttribute == NSLayoutAttribute.Top {
constraint.constant = -200
}
}
} else {
for constraint in constraint_V {
if constraint.firstAttribute == NSLayoutAttribute.Top {
constraint.constant = 10
}
}
}
completion = !completion
UIView.animateWithDuration(1, animations: {
self.view.layoutIfNeeded()
}, completion: {(value: Bool) in
})
You will ask me, why if it work in the ViewDidLoad you simply do not use it?
It's because my main problem is when I "presentViewController" and dismiss it, constraints break again and the only way I found to reproduce this bug is to insert my initialization into the ViewDidAppear.
I have commit and push my code into a github if you want to test with me: https://github.com/Comanga/Bug-Constraints.
What you need to see is the green view that is not stuck anymore to the top constraint.
Oh you read this until this line? Thank you <3
iOS9 - SWIFT 2.0

Answer 1

Hope this would help you
viewDidAppear is called finally after UIKit laid out sub views and displayed them.
So it is not working and you can think another way to re-layout your view controller after added/removed constraints.
try setNeedsUpdateConstraints or something