Fix potential data races

Tusker/Screens/Profile/ProfileViewController.swift

@@ -91,8 +91,8 @@ class ProfileViewController: UIPageViewController {
         addKeyCommand(MenuController.nextSubTabCommand)
         
         accountUpdater = mastodonController.persistentContainer.accountSubject
-            .filter { [weak self] in $0 == self?.accountID }
             .receive(on: DispatchQueue.main)
+            .filter { [weak self] in $0 == self?.accountID }
             .sink { [weak self] (_) in self?.updateAccountUI() }
         
         loadAccount()

Tusker/Views/Attachments/AttachmentView.swift

@@ -164,7 +164,9 @@ class AttachmentView: UIImageView, GIFAnimatable {
         let attachmentURL = attachment.url
         attachmentRequest = ImageCache.attachments.get(attachmentURL) { [weak self] (data, _) in
             guard let self = self, let data = data else { return }
+            DispatchQueue.main.async {
                 self.attachmentRequest = nil
+            }
             if self.attachment.url.pathExtension == "gif" {
                 self.source = .gifData(attachmentURL, data)
                 if self.autoplayGifs {

Tusker/Views/Profile Header/ProfileHeaderView.swift

@@ -80,14 +80,14 @@ class ProfileHeaderView: UIView {
         cancellables = []
         
         mastodonController.persistentContainer.accountSubject
-            .filter { [weak self] in $0 == self?.accountID }
             .receive(on: DispatchQueue.main)
+            .filter { [weak self] in $0 == self?.accountID }
             .sink { [weak self] in self?.updateUI(for: $0) }
             .store(in: &cancellables)
         
         mastodonController.persistentContainer.relationshipSubject
-            .filter { [weak self] in $0 == self?.accountID }
             .receive(on: DispatchQueue.main)
+            .filter { [weak self] in $0 == self?.accountID }
             .sink { [weak self] (_) in self?.updateRelationship() }
             .store(in: &cancellables)
     }
@@ -203,11 +203,14 @@ class ProfileHeaderView: UIView {
                   let image = image,
                   self.accountID == accountID,
                   let transformedImage = ImageGrayscalifier.convertIfNecessary(url: avatarURL, image: image) else {
+                DispatchQueue.main.async {
+                    self?.avatarRequest = nil
+                }
                 return
             }
-            self.avatarRequest = nil
             
             DispatchQueue.main.async {
+                self.avatarRequest = nil
                 self.avatarImageView.image = transformedImage
             }
         }
@@ -217,11 +220,14 @@ class ProfileHeaderView: UIView {
                       let image = image,
                       self.accountID == accountID,
                       let transformedImage = ImageGrayscalifier.convertIfNecessary(url: header, image: image) else {
+                    DispatchQueue.main.async {
+                        self?.headerRequest = nil
+                    }
                     return
                 }
-                self.headerRequest = nil
                 
                 DispatchQueue.main.async {
+                    self.headerRequest = nil
                     self.headerImageView.image = transformedImage
                 }
             }

Tusker/Views/Status/BaseStatusTableViewCell.swift

@@ -106,8 +106,8 @@ class BaseStatusTableViewCell: UITableViewCell, MenuPreviewProvider {
     open func createObserversIfNecessary() {
         if statusUpdater == nil {
             statusUpdater = mastodonController.persistentContainer.statusSubject
-                .filter { [unowned self] in $0 == self.statusID }
                 .receive(on: DispatchQueue.main)
+                .filter { [unowned self] in $0 == self.statusID }
                 .sink { [unowned self] in
                     if let mastodonController = mastodonController,
                        let status = mastodonController.persistentContainer.status(for: $0) {
@@ -118,8 +118,8 @@ class BaseStatusTableViewCell: UITableViewCell, MenuPreviewProvider {
 
         if accountUpdater == nil {
             accountUpdater = mastodonController.persistentContainer.accountSubject
-                .filter { [unowned self] in $0 == self.accountID }
                 .receive(on: DispatchQueue.main)
+                .filter { [unowned self] in $0 == self.accountID }
                 .sink { [unowned self] in
                     if let mastodonController = mastodonController,
                        let account = mastodonController.persistentContainer.account(for: $0) {

Tusker/Views/Status/TimelineStatusTableViewCell.swift

@@ -59,8 +59,8 @@ class TimelineStatusTableViewCell: BaseStatusTableViewCell {
         
         if rebloggerAccountUpdater == nil {
             rebloggerAccountUpdater = mastodonController.persistentContainer.accountSubject
-                .filter { [unowned self] in $0 == self.rebloggerID }
                 .receive(on: DispatchQueue.main)
+                .filter { [unowned self] in $0 == self.rebloggerID }
                 .sink { [unowned self] in
                     if let mastodonController = self.mastodonController,
                        let reblogger = mastodonController.persistentContainer.account(for: $0) {