Potential solution to http://inessential.com/2015/07/19/secret_projects_diary_2_swift_2_0_prot

RSSReaderExamplePlayground

//: # Brent's "Secret Projects Diary #2"
import Foundation
//: ## Feeds
protocol Feed: Equatable {
    var url: String {get}
}

class LocalFeed: Feed {
    var url: String
    init(url: String) {
        self.url = url
    }
    init<T: Feed>(feed: T) {
        self.url = feed.url
    }
}
func ==(lhs: LocalFeed, rhs: LocalFeed) -> Bool { return lhs.url == rhs.url }

class FeverFeed: Feed {
    enum Kind {
        case Kindling
        case Spark
    }
    var url: String
    var kind: FeverFeed.Kind
    init(url: String, kind: FeverFeed.Kind) {
        self.url = url
        self.kind = kind
    }
    init<T: Feed>(feed: T) {
        self.url = feed.url
        self.kind = .Spark // Must choose some default, or add to the init signature
    }
}
func ==(lhs: FeverFeed, rhs: FeverFeed) -> Bool { return lhs.url == rhs.url && lhs.kind == rhs.kind }
//: ## Folders
class Folder<T: Feed> {
    var feeds = [T]()
    func addFeeds(feedsToAdd: [T]) {
        for oneFeed in feedsToAdd {
            if !feeds.contains(oneFeed) {
                feeds += [oneFeed]
            }
        }
    }
}
//: ## Example Implementation
extension Folder {
    func domains() -> [String] {
        let urls = feeds.map { NSURL(string: $0.url)! }
        let domains = urls.map { String($0.host!) }
        return domains
    }
}

class LocalFolderGeneric<T: LocalFeed>: Folder<T> {
    func localFunction() -> String {
        return "Just Local Things"
    }
}

class FeverFolderGeneric<T: FeverFeed>: Folder<T> {
    func hotListKinds() -> [FeverFeed.Kind] {
        return feeds.map { $0.kind }
    }
}

typealias LocalFolder = LocalFolderGeneric<LocalFeed>
typealias FeverFolder = FeverFolderGeneric<FeverFeed>

let IN = "http://inessential.com/xml/rss.xml"
let BE = "https://www.youtube.com/user/BetterElevation"
let DF = "http://daringfireball.net/feeds/main"

let QBranch = [IN, BE, DF]

let localFeeds = QBranch.map { LocalFeed(url: $0) }
let localFolder = LocalFolder()
localFolder.addFeeds(localFeeds)
localFolder.localFunction()
localFolder.domains()

let MS = FeverFeed(url: "http://www.macstories.net/feed/", kind: .Spark)
let feverFeeds = QBranch.map { FeverFeed(url: $0, kind: .Kindling) } + [MS]
let feverFolder = FeverFolder()
feverFolder.addFeeds(feverFeeds)
feverFolder.hotListKinds()
feverFolder.domains()

Added initializations of specialized Feed classes from generic Feeds.

Added typealiases for LocalFolder and FeverFolder for some syntactic sugar.