Swift View and Controller shared variable initialization troubles - swift

Question

I'm porting some code from Objc to Swift. And struggling with Swift's initialization life cycle. From a simplified point of view, there are 4 players I'm trying to bring into play here:
An object called a Program. This is my main top level model object at this point. The remaining 3 players all want access to an instance of him.
A ProgramEditController, painted in my main Main.storyboard. He's responsible for instantiating an initial Program, which cannot be done directly as a property initializer.
A top level custom UIView subclass, called ProgramTimelineView. Painted in the Main.storyboard, manages a variety of specialized subviews. Linked to a property of my ViewController. Has properties for the it's subviews as well. It wants access to the Program, so it can do layout and pass it on to subviews.
A particular subview of ProgramTimelineView called ProgramGridView. These are not painted in the XCode canvas tool, but directly instantiated by the containing ProgramTimelineView. It wants access to the Program. Uses it to do his custom drawRect.
Here's the relevant code for my Controller:
class ProgramEditController: UIViewController {
// MARK: - Variables
#IBOutlet var timelineView:ProgramTimelinesView!
var site = Site()
var program:Program!
// MARK: - Initialize
override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
// set up the new program
self.program = self.site.newProgram()
// get it into our top view before it starts drawing
self.timelineView.program = self.program
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder) // Why does Swift make me have a redundant thing here?
}
}
And for ProgramTimelinesView:
class ProgramTimelinesView: UIView {
// MARK: - Variables
var gridView = ProgramGridView()
var program:Program! {
didSet {
self.gridView.program = self.program
}
}
// MARK: - Initialization
func addGridView() {
self.gridView.alpha = 0.0
self.gridView.opaque = false
self.addSubview(self.gridView)
}
func commonInit() {
self.addGridView()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.commonInit()
}
override init(frame: CGRect) {
super.init(frame: frame)
self.commonInit()
}
}
And finally for the ProgramGridView:
class ProgramGridView: TimeAxisView {
// MARK: - Variables
var program:Program!
override func drawRect(rect: CGRect) {
// access self.program in here
}
}
What I thought would happen:
ProgramEditController.init(nibName...) would fire first.
The super call would cause my ProgramTimelineView.init(coder) to fire.
ProgramTimelineView instance would first call the gridView initializer setting it to a new ProgramGridView view
The remainder of ProgramTimelineView.init(coder) would run, which would add the gridView into the view tree.
Control would return to the ProgramEditController.init(nibName) initializers. The controller's program property would be populated.
The bound timelineView would have its program property set.
ProgramTimelineView would in turn set the program property of the gridView.
What seems to happen though, between steps 4 and 5, is that a drawRect() happens. That causes a seg fault, because the gridView's program has not been set yet! But why is it issuing drawRect()'s at this point? I thought that wouldn't happen before all of the initializers had fired. But clearly some side affect is occurring. What is the correct pattern/idiom to employ to avoid this? I really would rather not turn all of the program! into program? and then put let/guards every where.

Answer 1

There turned out to be a faulty assumption in my original premises (usually the case).
UIViewController.init(nib...) is NOT called when creating from interface builder assets. But local variables linked in interface builder (implicitly wrapped) are not set/realized at the point of init(coder) either. The correct approach required two adjustments:
Move the setup of the program var to the init(coder) initializers:
e.g.
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.program = self.site.newProgram()
}
Forward that to the view in a viewDidLoad() override.
e.g.
override func viewDidLoad() {
super.viewDidLoad()
self.timelineView.program = self.program
}