Sadface

ItemGenerics.swift

//: Playground - noun: a place where people can play

import UIKit

protocol Item {
  
  var title: String? { get set }
  var value: String? { get set }
  
}

protocol ItemContainerViewDelegate {
  
  func itemContainerView<T: Item>(itemContainerView: ItemContainerView<T>, didSelectItem item: T?)
  
}

class ItemContainerView<T: Item>: UIView {
  
  var delegate: ItemContainerViewDelegate?
  
  func onTap() {
    
    // error: cannot convert value of type ItemContainerView<T> to expected argument type ItemContainerView<_>
    delegate?.itemContainerView(self, didSelectItem: nil)
    
  }
  
}

Actually it looks like @NachoSoto's suggestion won't work :(

protocol ItemContainerViewDelegate {
  associatedtype ItemType: Item

  // We need to declare ItemContainerView here as ItemContainerView<ItemType, Delegate> but that'd be referencing itself
  func itemContainerView(itemContainerView: ItemContainerView<ItemType>, didSelectItem item: ItemType?)  
}

// We need to declare ItemContainerView here as ItemContainerView<ItemType, Delegate> but that'd be referencing itself

@b3ll Oh yeah, I forgot about that. You could do type erasure, but I don't know if it's worth it. Do you really need to pass the entire ItemContainerView?

@NachoSoto well the cocoa way to do delegates is to pass back the original object that's firing the delegate, so without that it's not as useful. i.e. tableView:deselectRowAtIndexPath:animated:. I suppose I could pass back the index of the object, but that wouldn't be as nice than the object itself.

I'm not sure if type erasure is possible at this point, anything other than this I've tried has just lead to the compiler complaining about associatedtype dependencies :/