Can't add NSLayoutConstraints programmatically in Swift (no effect) - ios

Question

I've created a custom UIView subclass in Swift with a corresponding .xib file but am having trouble adding Auto Layout constraints during initialization. The view itself loads just fine, but adding layout constraints seems to have no effect on the view's layout, regardless of whether I add these constraints within init or viewDidMoveToSuperview or viewDidMoveToWindow, and even if I call setNeedsUpdateConstraints() / layoutIfNeeded() immediately after.
I can do this quite easily in Objective-C, so hopefully this is a very simple fix, but I can't figure out what I am doing wrong.
Here is my code:
var isLoading = false
class CustomSubview: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setup()
}
private lazy var view: UIView! = { [unowned self] in
let bundle = NSBundle(forClass: self.dynamicType)
let nibName = String(CustomSubview.self)
let nib = UINib(nibName: nibName, bundle: bundle)
return nib.instantiateWithOwner(self, options: nil)[0] as! UIView
}()
private func setup() {
if (isLoading) {
return
}
isLoading = true
// self.view.frame = self.bounds // this works but I want to use Auto Layout
// self.view.autoresizingMask = [UIViewAutoresizing.FlexibleWidth, UIViewAutoresizing.FlexibleHeight] // this works but I want to use Auto Layout
self.translatesAutoresizingMaskIntoConstraints = false // no effect
addSubview(self.view)
let views = Dictionary(dictionaryLiteral: ("view", self.view))
let horizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|[view]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)
self.addConstraints(horizontalConstraints)
NSLayoutConstraint.activateConstraints(horizontalConstraints) // this seems to do nothing
let verticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("V:|[view]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views)
self.addConstraints(verticalConstraints)
NSLayoutConstraint.activateConstraints(verticalConstraints) // this seems to do nothing
self.setNeedsUpdateConstraints()
self.layoutIfNeeded()
isLoading = false
}
}

Answer 1

I've reworked your class a bit to make it look a bit cleaner. I've omitted the loading Bool. Also I have no experience in creating views from a XIB file I pretty much left it almost untouched.
var isLoading = false
class CustomSubview: UIView {
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setup()
}
private lazy var customView: UIView = {
let bundle = NSBundle(forClass: self.dynamicType)
let nibName = String(CustomSubview.self)
let nib = UINib(nibName: nibName, bundle: bundle)
let customView = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
customView.translatesAutoresizingMaskIntoConstraints = false
return customView
}()
private func setup() {
if (isLoading) {
return
}
isLoading = true
addSubview(self.customView)
let views = ["customView": customView]
addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[customView]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views))
addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[customView]|", options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views))
isLoading = false
}
}
As for your aspect ratio constraint, you can set multiple constraint for your aspect ratio and set the active of those to true / false to switch between them.