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Last active August 29, 2015 14:25
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Potential solution to Brent's problem
//: Playground - noun: a place where people can play
import Cocoa
protocol Feed {
var url: String {get}
protocol Folder {
typealias FeedType
var feeds: [FeedType] {get}
func addFeeds(feedsToAdd: [FeedType])
class LocalFeed: Feed {
var url: String
init(url: String) {
self.url = url
extension LocalFeed: Equatable { }
func ==(lhs: LocalFeed, rhs: LocalFeed) -> Bool {
return lhs.url == rhs.url
class LocalFolder<F: Feed where F: Equatable>: Folder {
typealias FeedType = F
var feeds = [FeedType]()
func addFeeds(feedsToAdd: [FeedType]) {
for oneFeed in feedsToAdd {
if !feeds.contains(oneFeed) {
feeds += [oneFeed]
let folder = LocalFolder<LocalFeed>()
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Not sure if this satisfies all your requirements, but it seems like making Folder generic through an associated type might get you to where you want to be.

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