SubclassEquality.playground

class EventFeed: Hashable, Equatable {
    var eventId    = 0
    var hashValue  : Int { return eventId }
    
  func equals(another: EventFeed) -> Bool {
    return self.eventId === another.eventId
  }
}

func ==(lhs: EventFeed, rhs: EventFeed) -> Bool {
    return lsh.equals(rhs)
}

class PostUpload : EventFeed {

    var postId        : Int
    override var hashValue  : Int { return postId }

    init(id: Int) {
        postId = id
    }
    
  func equals(another: EventFeed) -> Bool {
    return self.postId === another.posttId
  }
}

var postQueue = [PostUpload]()
let importantPost = PostUpload(id: 12)

postQueue.append(PostUpload(id: 10))
postQueue.append(importantPost)

//this should be 1, not 0
let index = postQueue.indexOf(importantPost)