Made launch performance *much* faster for large (thousands of feeds) subscriptions list. Also: split container.children in container.topLevelFeeds and container.folders. This simplifies a bunch of things, and makes some things faster.

Frameworks/Account/Account.swift

@@ -37,6 +37,7 @@ public enum AccountType: Int {
 
 public final class Account: DisplayNameProvider, UnreadCountProvider, Container, Hashable {
 
+
     public struct UserInfoKey {
 		public static let newArticles = "newArticles" // AccountDidDownloadArticles
 		public static let updatedArticles = "updatedArticles" // AccountDidDownloadArticles
@@ -48,8 +49,20 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 	public let accountID: String
 	public let type: AccountType
 	public var nameForDisplay = ""
-	public var children = [AnyObject]()
-	var idToFeedDictionary = [String: Feed]()
+	public var topLevelFeeds = Set<Feed>()
+	public var folders: Set<Folder>? = Set<Folder>()
+
+	private var feedDictionaryNeedsUpdate = true
+	private var _idToFeedDictionary = [String: Feed]()
+	var idToFeedDictionary: [String: Feed] {
+		if feedDictionaryNeedsUpdate {
+			rebuildFeedDictionaries()
+		}
+		return _idToFeedDictionary
+	}
+
+	private var fetchingAllUnreadCounts = false
+
 	let settingsFile: String
 	let dataFolder: String
 	let database: ArticlesDatabase
@@ -65,6 +78,9 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 	private var unreadCounts = [String: Int]() // [feedID: Int]
 	private let opmlFilePath: String
 
+	private var _flattenedFeeds = Set<Feed>()
+	private var flattenedFeedsNeedUpdate = true
+
 	private struct SettingsKey {
 		static let unreadCount = "unreadCount"
 	}
@@ -204,7 +220,7 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 		}
 
 		let folder = Folder(account: self, name: name)
-		children += [folder]
+		folders!.insert(folder)
 		dirty = true
 
 		postChildrenDidChangeNotification()
@@ -244,21 +260,30 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 			didAddFeed = folder.addFeed(feed)
 		}
 		else {
-			if !topLevelObjectsContainsFeed(feed) {
-				children += [feed]
+			if !topLevelFeeds.contains(feed) {
+				topLevelFeeds.insert(feed)
 				postChildrenDidChangeNotification()
+				didAddFeed = true
 			}
-			didAddFeed = true
 		}
 
 		if didAddFeed {
-			addToFeedDictionaries(feed)
-			dirty = true
+			structureDidChange()
 		}
-		
+
 		return didAddFeed
 	}
 
+	public func addFeeds(_ feeds: Set<Feed>, to folder: Folder?) {
+		if let folder = folder {
+			folder.addFeeds(feeds)
+		}
+		else {
+			topLevelFeeds.formUnion(feeds)
+		}
+		structureDidChange()
+	}
+
 	public func createFeed(with name: String?, editedName: String?, url: String) -> Feed? {
 		
 		// For syncing, this may need to be an async method with a callback,
@@ -285,13 +310,12 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 
 		// TODO: support subfolders, maybe, some day, if one of the sync systems
 		// supports subfolders. But, for now, parentFolder is ignored.
-
-		if objectIsChild(folder) {
+		if folders!.contains(folder) {
 			return true
 		}
-		children += [folder]
+		folders!.insert(folder)
 		postChildrenDidChangeNotification()
-		rebuildFeedDictionaries()
+		structureDidChange()
 		return true
 	}
 
@@ -300,9 +324,8 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 		guard let children = opmlDocument.children else {
 			return
 		}
-		rebuildFeedDictionaries()
 		importOPMLItems(children, parentFolder: nil)
-		saveToDisk()
+		structureDidChange()
 
 		DispatchQueue.main.async {
 			self.refreshAll()
@@ -450,6 +473,35 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 		unreadCounts[feed.feedID] = unreadCount
 	}
 
+	public func structureDidChange() {
+		// Feeds were added or deleted. Or folders added or deleted.
+		// Or feeds inside folders were added or deleted.
+		dirty = true
+		flattenedFeedsNeedUpdate = true
+		feedDictionaryNeedsUpdate = true
+	}
+
+	// MARK: - Container
+
+	public func flattenedFeeds() -> Set<Feed> {
+		if flattenedFeedsNeedUpdate {
+			updateFlattenedFeeds()
+		}
+		return _flattenedFeeds
+	}
+
+	public func deleteFeed(_ feed: Feed) {
+		topLevelFeeds.remove(feed)
+		structureDidChange()
+		postChildrenDidChangeNotification()
+	}
+
+	public func deleteFolder(_ folder: Folder) {
+		folders?.remove(folder)
+		structureDidChange()
+		postChildrenDidChangeNotification()
+	}
+
 	// MARK: - Debug
 
 	public func debugDropConditionalGetInfo() {
@@ -482,6 +534,7 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
     
     @objc func batchUpdateDidPerform(_ note: Notification) {
 
+		flattenedFeedsNeedUpdate = true
 		rebuildFeedDictionaries()
         updateUnreadCount()
     }
@@ -492,17 +545,17 @@ public final class Account: DisplayNameProvider, UnreadCountProvider, Container,
 			return
 		}
 		if let account = object as? Account, account === self {
-			dirty = true
+			structureDidChange()
 		}
 		if let folder = object as? Folder, folder.account === self {
-			dirty = true
+			structureDidChange()
 		}
 	}
 
 	@objc func displayNameDidChange(_ note: Notification) {
 
 		if let folder = note.object as? Folder, folder.account === self {
-			dirty = true
+			structureDidChange()
 		}
 	}
 
@@ -582,11 +635,20 @@ private extension Account {
 			guard let childrenArray = d[Key.children] as? [[String: Any]] else {
 				return
 			}
-			children = objects(with: childrenArray)
-			rebuildFeedDictionaries()
-
-			let userInfo = d[Key.userInfo] as? NSDictionary
-			delegate.update(account: self, withUserInfo: userInfo)
+			let children = objects(with: childrenArray)
+			var feeds = Set<Feed>()
+			var folders = Set<Folder>()
+			for oneChild in children {
+				if let feed = oneChild as? Feed {
+					feeds.insert(feed)
+				}
+				else if let folder = oneChild as? Folder {
+					folders.insert(folder)
+				}
+			}
+			self.topLevelFeeds = feeds
+			self.folders = folders
+			structureDidChange()
 
 			// Rename plist file so we don’t see it next time.
 			let renamedFilePath = (dataFolder as NSString).appendingPathComponent("AccountData-old.plist")
@@ -624,11 +686,13 @@ private extension Account {
 			NSApplication.shared.presentError(error)
 			return
 		}
-		guard let parsedOPML = opmlDocument else {
+		guard let parsedOPML = opmlDocument, let children = parsedOPML.children else {
 			return
 		}
 
-		importOPML(parsedOPML)
+		BatchUpdate.shared.perform {
+			importOPMLItems(children, parentFolder: nil)
+		}
 	}
 
 	func saveToDisk() {
@@ -650,50 +714,47 @@ private extension Account {
 
 private extension Account {
 
+	func updateFlattenedFeeds() {
+		var feeds = Set<Feed>()
+		feeds.formUnion(topLevelFeeds)
+		for folder in folders! {
+			feeds.formUnion(folder.flattenedFeeds())
+		}
+
+		_flattenedFeeds = feeds
+		flattenedFeedsNeedUpdate = false
+	}
+
 	func rebuildFeedDictionaries() {
 
-		var urlDictionary = [String: Feed]()
 		var idDictionary = [String: Feed]()
 
 		flattenedFeeds().forEach { (feed) in
-			urlDictionary[feed.url] = feed
 			idDictionary[feed.feedID] = feed
 		}
 
-		idToFeedDictionary = idDictionary
-	}
-
-	func addToFeedDictionaries(_ feed: Feed) {
-
-		idToFeedDictionary[feed.feedID] = feed
-	}
-
-	func topLevelObjectsContainsFeed(_ feed: Feed) -> Bool {
-		
-		return children.contains(where: { (object) -> Bool in
-			if let oneFeed = object as? Feed {
-				if oneFeed.feedID == feed.feedID {
-					return true
-				}
-			}
-			return false
-		})
+		_idToFeedDictionary = idDictionary
+		feedDictionaryNeedsUpdate = false
 	}
 
 	func createFeed(with opmlFeedSpecifier: RSOPMLFeedSpecifier) -> Feed {
 
 		let feed = Feed(account: self, url: opmlFeedSpecifier.feedURL, feedID: opmlFeedSpecifier.feedURL)
-		feed.editedName = opmlFeedSpecifier.title
+		if let feedTitle = opmlFeedSpecifier.title, feed.editedName == nil {
+			feed.editedName = feedTitle
+		}
 		return feed
 	}
 
 	func importOPMLItems(_ items: [RSOPMLItem], parentFolder: Folder?) {
 
+		var feedsToAdd = Set<Feed>()
+
 		items.forEach { (item) in
 
 			if let feedSpecifier = item.feedSpecifier {
 				let feed = createFeed(with: feedSpecifier)
-				addFeed(feed, to: parentFolder)
+				feedsToAdd.insert(feed)
 				return
 			}
 
@@ -713,11 +774,21 @@ private extension Account {
 				importOPMLItems(itemChildren, parentFolder: folder)
 			}
 		}
+
+		if !feedsToAdd.isEmpty {
+			addFeeds(feedsToAdd, to: parentFolder)
+		}
 	}
     
     func updateUnreadCount() {
-
-		unreadCount = calculateUnreadCount(flattenedFeeds())
+		if fetchingAllUnreadCounts {
+			return
+		}
+		var updatedUnreadCount = 0
+		for feed in flattenedFeeds() {
+			updatedUnreadCount += feed.unreadCount
+		}
+		unreadCount = updatedUnreadCount
     }
     
     func noteStatusesForArticlesDidChange(_ articles: Set<Article>) {
@@ -734,6 +805,7 @@ private extension Account {
 
 	func fetchAllUnreadCounts() {
 
+		fetchingAllUnreadCounts = true
 		database.fetchAllNonZeroUnreadCounts { (unreadCountDictionary) in
 
 			if unreadCountDictionary.isEmpty {
@@ -751,6 +823,7 @@ private extension Account {
 					feed.unreadCount = 0
 				}
 			}
+			self.fetchingAllUnreadCounts = false
 			self.updateUnreadCount()
 		}
 	}
@@ -764,6 +837,7 @@ extension Account {
 
 		return idToFeedDictionary[feedID]
 	}
+
 }
 
 // MARK: - OPMLRepresentable
@@ -773,10 +847,11 @@ extension Account: OPMLRepresentable {
 	public func OPMLString(indentLevel: Int) -> String {
 
 		var s = ""
-		for oneObject in children {
-			if let oneOPMLObject = oneObject as? OPMLRepresentable {
-				s += oneOPMLObject.OPMLString(indentLevel: indentLevel + 1)
-			}
+		for feed in topLevelFeeds {
+			s += feed.OPMLString(indentLevel: indentLevel + 1)
+		}
+		for folder in folders! {
+			s += folder.OPMLString(indentLevel: indentLevel + 1)
 		}
 		return s
 	}

Frameworks/Account/Container.swift

@@ -18,7 +18,8 @@ extension Notification.Name {
 
 public protocol Container: class {
 
-	var children: [AnyObject] { get set }
+	var topLevelFeeds: Set<Feed> { get set }
+	var folders: Set<Folder>? { get set }
 
 	func hasAtLeastOneFeed() -> Bool
 	func objectIsChild(_ object: AnyObject) -> Bool
@@ -29,7 +30,7 @@ public protocol Container: class {
     func deleteFeed(_ feed: Feed)
     func deleteFolder(_ folder: Folder)
     
-	//Recursive
+	//Recursive — checks subfolders
 	func flattenedFeeds() -> Set<Feed>
 	func hasFeed(with feedID: String) -> Bool
 	func hasFeed(withURL url: String) -> Bool
@@ -44,43 +45,31 @@ public protocol Container: class {
 public extension Container {
 
 	func hasAtLeastOneFeed() -> Bool {
-
-		for child in children {
-			if child is Feed {
-				return true
-			}
-			if let folder = child as? Folder {
-				if folder.hasAtLeastOneFeed() {
-					return true
-				}
-			}
-		}
-
-		return false
+		return topLevelFeeds.count > 0
 	}
 
 	func hasChildFolder(with name: String) -> Bool {
-
 		return childFolder(with: name) != nil
 	}
 
 	func childFolder(with name: String) -> Folder? {
-
-		for child in children {
-			if let folder = child as? Folder, folder.name == name {
+		guard let folders = folders else {
+			return nil
+		}
+		for folder in folders {
+			if folder.name == name {
 				return folder
 			}
 		}
-
 		return nil
 	}
 
 	func objectIsChild(_ object: AnyObject) -> Bool {
-
-		for child in children {
-			if object === child {
-				return true
-			}
+		if let feed = object as? Feed {
+			return topLevelFeeds.contains(feed)
+		}
+		if let folder = object as? Folder {
+			return folders?.contains(folder) ?? false
 		}
 		return false
 	}
@@ -88,123 +77,74 @@ public extension Container {
 	func flattenedFeeds() -> Set<Feed> {
 
 		var feeds = Set<Feed>()
-
-		for object in children {
-			if let feed = object as? Feed {
-				feeds.insert(feed)
-			}
-			else if let container = object as? Container {
-				feeds.formUnion(container.flattenedFeeds())
+		feeds.formUnion(topLevelFeeds)
+		if let folders = folders {
+			for folder in folders {
+				feeds.formUnion(folder.flattenedFeeds())
 			}
 		}
-
 		return feeds
 	}
 
 	func hasFeed(with feedID: String) -> Bool {
-
 		return existingFeed(with: feedID) != nil
 	}
 
 	func hasFeed(withURL url: String) -> Bool {
-
 		return existingFeed(withURL: url) != nil
 	}
 
 	func existingFeed(with feedID: String) -> Feed? {
-
-		for child in children {
-
-			if let feed = child as? Feed, feed.feedID == feedID {
-				return feed
-			}
-			if let container = child as? Container, let feed = container.existingFeed(with: feedID) {
+		for feed in flattenedFeeds() {
+			if feed.feedID == feedID {
 				return feed
 			}
 		}
-
 		return nil
 	}
 
 	func existingFeed(withURL url: String) -> Feed? {
-
-		for child in children {
-
-			if let feed = child as? Feed, feed.url == url {
-				return feed
-			}
-			if let container = child as? Container, let feed = container.existingFeed(withURL: url) {
+		for feed in flattenedFeeds() {
+			if feed.url == url {
 				return feed
 			}
 		}
-
 		return nil
 	}
 
 	func existingFolder(with name: String) -> Folder? {
-
-		for child in children {
-
-			if let folder = child as? Folder {
-				if folder.name == name {
-					return folder
-				}
-				if let subFolder = folder.existingFolder(with: name) {
-					return subFolder
-				}
-			}
+		guard let folders = folders else {
+			return nil
 		}
 
+		for folder in folders {
+			if folder.name == name {
+				return folder
+			}
+			if let subFolder = folder.existingFolder(with: name) {
+				return subFolder
+			}
+		}
 		return nil
 	}
 
 	func existingFolder(withID folderID: Int) -> Folder? {
-
-		for child in children {
-
-			if let folder = child as? Folder {
-				if folder.folderID == folderID {
-					return folder
-				}
-				if let subFolder = folder.existingFolder(withID: folderID) {
-					return subFolder
-				}
-			}
+		guard let folders = folders else {
+			return nil
 		}
 
+		for folder in folders {
+			if folder.folderID == folderID {
+				return folder
+			}
+			if let subFolder = folder.existingFolder(withID: folderID) {
+				return subFolder
+			}
+		}
 		return nil
 	}
 
-    func indexOf<T: Equatable>(_ object: T) -> Int? {
-        
-        return children.index(where: { (child) -> Bool in
-            if let oneObject = child as? T {
-                return oneObject == object
-            }
-            return false
-        })
-    }
-    
-    func delete<T: Equatable>(_ object: T) {
-        
-        if let index = indexOf(object) {
-            children.remove(at: index)
-            postChildrenDidChangeNotification()
-        }
-    }
-    
-    func deleteFeed(_ feed: Feed) {
-        
-        return delete(feed)
-    }
-    
-    func deleteFolder(_ folder: Folder) {
-        
-        return delete(folder)
-    }
-    
 	func postChildrenDidChangeNotification() {
-		
 		NotificationCenter.default.post(name: .ChildrenDidChange, object: self)
 	}
 }

Frameworks/Account/Folder.swift

@@ -10,11 +10,13 @@ import Foundation
 import Articles
 import RSCore
 
-public final class Folder: DisplayNameProvider, Container, UnreadCountProvider, Hashable {    
+public final class Folder: DisplayNameProvider, Container, UnreadCountProvider, Hashable {
+
 
 	public weak var account: Account?
-	public var children = [AnyObject]()
-
+	public var topLevelFeeds: Set<Feed> = Set<Feed>()
+	public var folders: Set<Folder>? = nil // subfolders are not supported, so this is always nil
+	
 	public var name: String? {
 		didSet {
 			postDisplayNameDidChangeNotification()
@@ -69,21 +71,28 @@ public final class Folder: DisplayNameProvider, Container, UnreadCountProvider,
 		self.init(account: account, name: name)
 
 		if let childrenArray = dictionary[Key.children] as? [[String: Any]] {
-			self.children = Folder.objects(with: childrenArray, account: account)
+			self.topLevelFeeds = Folder.feedsOnly(with: childrenArray, account: account)
 		}
 	}
 
 	// MARK: Feeds
-	
+
+	/// Add a single feed. Return true if number of feeds in folder changes.
 	func addFeed(_ feed: Feed) -> Bool {
-		
-		// Return true in the case where the feed is already a child.
-		
-		if !childrenContain(feed) {
-			children += [feed]
+		return addFeeds(Set([feed]))
+	}
+
+	/// Add one or more feeds. Return true if number of feeds in folder changes.
+	@discardableResult
+	func addFeeds(_ feedsToAdd: Set<Feed>) -> Bool {
+		let feedCount = topLevelFeeds.count
+		topLevelFeeds.formUnion(feedsToAdd)
+
+		if feedCount != topLevelFeeds.count {
 			postChildrenDidChangeNotification()
+			return true
 		}
-		return true
+		return false
 	}
     
 	// MARK: - Notifications
@@ -102,6 +111,30 @@ public final class Folder: DisplayNameProvider, Container, UnreadCountProvider,
 		updateUnreadCount()
 	}
 
+	// MARK: Container
+
+	public func flattenedFeeds() -> Set<Feed> {
+		// Since sub-folders are not supported, it’s always the top-level feeds.
+		return topLevelFeeds
+	}
+
+	public func objectIsChild(_ object: AnyObject) -> Bool {
+		// Folders contain Feed objects only, at least for now.
+		guard let feed = object as? Feed else {
+			return false
+		}
+		return topLevelFeeds.contains(feed)
+	}
+
+	public func deleteFeed(_ feed: Feed) {
+		topLevelFeeds.remove(feed)
+		postChildrenDidChangeNotification()
+	}
+
+	public func deleteFolder(_ folder: Folder) {
+		// Nothing to do
+	}
+
 	// MARK: - Hashable
 
 	public func hash(into hasher: inout Hasher) {
@@ -121,17 +154,15 @@ public final class Folder: DisplayNameProvider, Container, UnreadCountProvider,
 private extension Folder {
 
 	func updateUnreadCount() {
-		
-		unreadCount = calculateUnreadCount(children)
+		var updatedUnreadCount = 0
+		for feed in topLevelFeeds {
+			updatedUnreadCount += feed.unreadCount
+		}
+		unreadCount = updatedUnreadCount
 	}
 
 	func childrenContain(_ feed: Feed) -> Bool {
-		return children.contains(where: { (object) -> Bool in
-			if let oneFeed = object as? Feed {
-				return oneFeed == feed
-			}
-			return false
-		})
+		return topLevelFeeds.contains(feed)
 	}
 }
 
@@ -139,17 +170,6 @@ private extension Folder {
 
 private extension Folder {
 
-	static func objects(with diskObjects: [[String: Any]], account: Account) -> [AnyObject] {
-
-		if account.supportsSubFolders {
-			return account.objects(with: diskObjects)
-		}
-		else {
-			let flattenedFeeds = feedsOnly(with: diskObjects, account: account)
-			return Array(flattenedFeeds) as [AnyObject]
-		}
-	}
-
 	static func feedsOnly(with diskObjects: [[String: Any]], account: Account) -> Set<Feed> {
 
 		// This Folder doesn’t support subfolders, but they might exist on disk.
@@ -187,11 +207,9 @@ extension Folder: OPMLRepresentable {
 
 		var hasAtLeastOneChild = false
 
-		for child in children  {
-			if let opmlObject = child as? OPMLRepresentable {
-				s += opmlObject.OPMLString(indentLevel: indentLevel + 1)
-				hasAtLeastOneChild = true
-			}
+		for feed in topLevelFeeds  {
+			s += feed.OPMLString(indentLevel: indentLevel + 1)
+			hasAtLeastOneChild = true
 		}
 
 		if !hasAtLeastOneChild {

NetNewsWire/MainWindow/AddFeed/FolderTreeControllerDelegate.swift

@@ -27,15 +27,10 @@ private extension FolderTreeControllerDelegate {
 		// Root node is “Top Level” and children are folders. Folders can’t have subfolders.
 		// This will have to be revised later.
 
-		var folderNodes = [Node]()
-
-		for oneRepresentedObject in AccountManager.shared.localAccount.children {
-
-			if let folder = oneRepresentedObject as? Folder {
-				folderNodes += [createNode(folder, parent: node)]
-			}
+		guard let folders = AccountManager.shared.localAccount.folders else {
+			return nil
 		}
-
+		let folderNodes = folders.map { createNode($0, parent: node) }
 		return folderNodes.sortedAlphabetically()
 	}
 

NetNewsWire/MainWindow/Sidebar/SidebarTreeControllerDelegate.swift

@@ -51,9 +51,15 @@ private extension SidebarTreeControllerDelegate {
 
 		let container = containerNode.representedObject as! Container
 
+		var children = [AnyObject]()
+		children.append(contentsOf: Array(container.topLevelFeeds))
+		if let folders = container.folders {
+			children.append(contentsOf: Array(folders))
+		}
+
 		var updatedChildNodes = [Node]()
 
-		container.children.forEach { (representedObject) in
+		children.forEach { (representedObject) in
 
 			if let existingNode = containerNode.childNodeRepresentingObject(representedObject) {
 				if !updatedChildNodes.contains(existingNode) {

NetNewsWire/Scriptability/Account+Scriptability.swift

@@ -68,34 +68,35 @@ class ScriptableAccount: NSObject, UniqueIdScriptingObject, ScriptingObjectConta
     
     @objc(feeds)
     var feeds:NSArray  {
-        let feeds = account.children.compactMap { $0 as? Feed }
-        return feeds.map { ScriptableFeed($0, container:self) } as NSArray
+        return account.topLevelFeeds.map { ScriptableFeed($0, container:self) } as NSArray
     }
     
     @objc(valueInFeedsWithUniqueID:)
     func valueInFeeds(withUniqueID id:String) -> ScriptableFeed? {
-        let feeds = account.children.compactMap { $0 as? Feed }
+        let feeds = Array(account.topLevelFeeds)
         guard let feed = feeds.first(where:{$0.feedID == id}) else { return nil }
         return ScriptableFeed(feed, container:self)
     }
     
     @objc(valueInFeedsWithName:)
     func valueInFeeds(withName name:String) -> ScriptableFeed? {
-        let feeds = account.children.compactMap { $0 as? Feed }
+		let feeds = Array(account.topLevelFeeds)
         guard let feed = feeds.first(where:{$0.name == name}) else { return nil }
         return ScriptableFeed(feed, container:self)
     }
 
     @objc(folders)
     var folders:NSArray  {
-        let folders = account.children.compactMap { $0 as? Folder }
-        return folders.map { ScriptableFolder($0, container:self) } as NSArray
+		let foldersSet = account.folders ?? Set<Folder>()
+		let folders = Array(foldersSet)
+		return folders.map { ScriptableFolder($0, container:self) } as NSArray
     }
     
     @objc(valueInFoldersWithUniqueID:)
     func valueInFolders(withUniqueID id:NSNumber) -> ScriptableFolder? {
         let folderId = id.intValue
-        let folders = account.children.compactMap { $0 as? Folder }
+		let foldersSet = account.folders ?? Set<Folder>()
+		let folders = Array(foldersSet)
         guard let folder = folders.first(where:{$0.folderID == folderId}) else { return nil }
         return ScriptableFolder(folder, container:self)
     }    
@@ -105,14 +106,15 @@ class ScriptableAccount: NSObject, UniqueIdScriptingObject, ScriptingObjectConta
     @objc(contents)
     var contents:NSArray  {
         var contentsArray:[AnyObject] = []
-        for child in account.children {
-            if let aFeed = child as? Feed {
-                contentsArray.append(ScriptableFeed(aFeed, container:self))
-            } else if let aFolder = child as? Folder {
-                contentsArray.append(ScriptableFolder(aFolder, container:self))
-            }
-        }
-        return contentsArray as NSArray
+		for feed in account.topLevelFeeds {
+			contentsArray.append(ScriptableFeed(feed, container: self))
+		}
+		if let folders = account.folders {
+			for folder in folders {
+				contentsArray.append(ScriptableFolder(folder, container:self))
+			}
+		}
+		return contentsArray as NSArray
     }
 
     @objc(opmlRepresentation)

NetNewsWire/Scriptability/Folder+Scriptability.swift

@@ -92,7 +92,7 @@ class ScriptableFolder: NSObject, UniqueIdScriptingObject, ScriptingObjectContai
     
     @objc(feeds)
     var feeds:NSArray  {
-        let feeds = folder.children.compactMap { $0 as? Feed }
+		let feeds = Array(folder.topLevelFeeds)
         return feeds.map { ScriptableFeed($0, container:self) } as NSArray
     }
 

NetNewsWire/Scriptability/NSApplication+Scriptability.swift

@@ -77,7 +77,7 @@ extension NSApplication : ScriptingObjectContainer {
         let accounts = AccountManager.shared.accounts
         let emptyFeeds:[Feed] = []
         return accounts.reduce(emptyFeeds) { (result, nthAccount) -> [Feed] in
-              let accountFeeds = nthAccount.children.compactMap { $0 as? Feed }
+              let accountFeeds = Array(nthAccount.topLevelFeeds)
               return result + accountFeeds
         }
     }