SubclassEquality.playground

class EventFeed: Hashable, Equatable {
    var eventId    = 0
    var hashValue  : Int { return eventId }
}

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

class PostUpload : EventFeed {

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

    init(id: Int) {
        postId = id
    }
}

func ==(lhs: PostUpload, rhs: PostUpload) -> Bool {
    return lhs.postId == rhs.postId
}

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)