delegate is always nil - swift

Question

I have a custom UIView class called MyView and a View Controller.
When the user taps a button on the UIView, I want to call a function on the view controller. I'm trying to achieve this through delegation
custom UIClass
#objc protocol MyViewDelegate{
optional func expandCollapse()
}
class MyView: UIView, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource, UICollectionViewDelegate{
weak var delegate:MyViewDelegate?
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
if self.subviews.count == 0 {
loadNib()
}
}
override init(frame:CGRect){
super.init(frame: frame)
loadNib()
}
func loadNib(){
let bundle = NSBundle(forClass: self.dynamicType)
let nib = UINib(nibName: "MyView", bundle: bundle)
let view = nib.instantiateWithOwner(self, options: nil)[0] as! MyView
view.frame = bounds
view.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
self.addSubview(view);
}
#IBAction func expandit(sender: AnyObject) {
//this is where it fails. delegate is nil
delegate!.expandCollapse!()
}
}
My View Controller
class ViewController2: UIViewController, MyViewDelegate {
#IBOutlet weak var theview: UIView!
var myview : MyView?
override func viewDidAppear(animated: Bool) {
super.viewWillAppear(animated)
myview = MyView(frame: CGRectMake(0,0,theview.frame.size.width,theview.frame.size.height))
self.theview.addSubview(myview!)
myview!.delegate = self
}
func expandCollapse() {
viewheight.constant = 172
UIView.animateWithDuration(0.5) {
self.view.layoutIfNeeded()
}
}
In the UIView, the delegate is always nil. What am I missing?

Answer 1

Using delegation for this is simply unsuitable. You are fighting UIKit design patterns.
The whole situation is very simple.
You have your ViewController.
Then you have your totally independent custom view.
Essentially, you want somehow to route the TouchUpInside event from the button to get to viewController.
If your Custom view contains a button, then the accessibility level of this button is internal by default. Looking at the code, I assume you created the button in Interface builder. Make an outlet from the custom view class to the button, so that there is a programatically accessible reference to it.
Your view controller declares an instance of this custom view. Then, in viewDidLoad you have to use the target-action pattern.
self.customView.button.addTarget(target: self, action: "expandCollapse", forControlEvents: .TouchUpInside)
That's basically all there is to it.

Answer 2

I'm not entirely confident of my ARC understanding, but I believe the issue is that your delegate is a weak reference and there's nothing keeping a reference to the delegate after it's set, so it' deallocated.
Replace it with this and I believe it will work:
var delegate:MyViewDelegate?

Answer 3

Try assigning the delegate to "myview" before adding it to "theview"

Answer 4

The problem is in the loadNib() member function.
You're creating two instances of "MyView". The second instance being added as a subview.
You're setting the delegate in one instance and referring to a nil delegate in the other instance.
Try using a static class method like below to create one instance of "MyView"
class func loadFromNib() -> MyView? {
guard let myView = Bundle.main.loadNibNamed("MyView", owner: nil, options: nil)?.first as? MyView else {
assertionFailure("Failed to load nib for 'MyView'!")
return nil
}
return myView
}
Doing it this way, you won't need the custom init()s either.
Hope that helps!