From 13007d0acbcbc198bc6bbaa90c1dc89f3b83f912 Mon Sep 17 00:00:00 2001
From: Michael Brown <me@michael-brown.net>
Date: Tue, 24 May 2016 23:13:34 +0100
Subject: [PATCH] Fixes bug with GridView reloading unexpectedly.

---
 Memories/Grid View/GridViewModel.swift        | 27 +++++++++----------
 Memories/Photo View/PhotoViewController.swift | 26 +++++++++++++++---
 2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/Memories/Grid View/GridViewModel.swift b/Memories/Grid View/GridViewModel.swift
index b954213..865510b 100644
--- a/Memories/Grid View/GridViewModel.swift	
+++ b/Memories/Grid View/GridViewModel.swift	
@@ -12,13 +12,7 @@ import PHAssetHelper
 
 class GridViewModel {
     private let assetHelper = PHAssetHelper()
-    private var assetFetchResults = [PHFetchResult]() {
-        didSet {
-            dispatch_async(dispatch_get_main_queue()) { [unowned self] in
-                self.onDataChanged(self.date.value)
-            }
-        }
-    }
+    private var assetFetchResults = [PHFetchResult]()
     
     let date : Dynamic<NSDate>
     let onDataChanged: (NSDate) -> ()
@@ -33,10 +27,7 @@ class GridViewModel {
         self.onDataChanged = onDataChanged
         self.date = Dynamic(NSDate())
         self.date.bind {
-            let date = $0
-            dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { [unowned self] in
-                self.assetFetchResults = self.assetHelper.fetchResultsForDateInAllYears(date)
-            }
+            self.fetchDataAndNotify($0)
         }
     }
     
@@ -44,13 +35,19 @@ class GridViewModel {
         self.onDataChanged = onDataChanged
         self.date = Dynamic(date)
         self.date.bindAndFire {
-            let date = $0
-            dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { [unowned self] in
-                self.assetFetchResults = self.assetHelper.fetchResultsForDateInAllYears(date)
-            }
+            self.fetchDataAndNotify($0)
         }
     }
 
+    private func fetchDataAndNotify(date: NSDate) {
+        dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { [unowned self] in
+            self.assetFetchResults = self.assetHelper.fetchResultsForDateInAllYears(date)
+            dispatch_async(dispatch_get_main_queue()) { [unowned self] in
+                self.onDataChanged(self.date.value)
+            }
+        }
+    }
+    
     // MARK: - API
     func goToNextDay() {
         date.value = date.value.nextDay()
diff --git a/Memories/Photo View/PhotoViewController.swift b/Memories/Photo View/PhotoViewController.swift
index c274560..76e451a 100644
--- a/Memories/Photo View/PhotoViewController.swift	
+++ b/Memories/Photo View/PhotoViewController.swift	
@@ -141,8 +141,10 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
     @IBAction func close(sender: UIButton) {
         if let navController = presentingViewController as? UINavigationController,
             gridViewController = navController.topViewController as? GridViewController {
+            cancelAllImageRequests()
+            PHPhotoLibrary.sharedPhotoLibrary().unregisterChangeObserver(self)
+
             gridViewController.setSelectedIndex(model.selectedIndex)
-            
             if traitCollection.verticalSizeClass == .Regular {
                 hideStatusBar(false)
             }
@@ -268,7 +270,7 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
         options.deliveryMode = .HighQualityFormat
         options.synchronous = false
         
-        let requestId = PHImageManager.defaultManager().requestImageForAsset(asset, targetSize: PHImageManagerMaximumSize, contentMode: .AspectFit, options: options) { (result, userInfo) -> Void in
+        pageView.imageRequestId = PHImageManager.defaultManager().requestImageForAsset(asset, targetSize: PHImageManagerMaximumSize, contentMode: .AspectFit, options: options) { (result, userInfo) -> Void in
             if let image = result {
                 UpgradeManager.highQualityViewCount += 1
                 pageView.image = image
@@ -289,8 +291,6 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
                 pageView.fullImageUnavailable = true
             }
         }
-        
-        pageView.imageRequestId = requestId
     }
     
     func purgePage(page: Int) {
@@ -302,6 +302,7 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
         if let pageView = pageViews[page] {
             if let requestId = pageView.imageRequestId {
                 PHImageManager.defaultManager().cancelImageRequest(requestId)
+                pageView.imageRequestId = nil
             }
             pageView.image = nil
             pageView.removeFromSuperview()
@@ -309,6 +310,19 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
         }
     }
     
+    func cancelPageImageRequest(page: Int) {
+        guard page >= 0 && page < pageViews.count else {
+            return
+        }
+        
+        if let pageView = pageViews[page] {
+            if let requestId = pageView.imageRequestId {
+                PHImageManager.defaultManager().cancelImageRequest(requestId)
+                pageView.imageRequestId = nil
+            }
+        }
+    }
+    
     func loadVisiblePages() {
         let initialLoad = !initialOffsetSet
         
@@ -343,6 +357,10 @@ class PhotoViewController: UIViewController, UIScrollViewDelegate, UIViewControl
         model.assets.count.stride(to: lastPage, by: -1).forEach(purgePage)
     }
     
+    func cancelAllImageRequests() {
+        pageViews.indices.forEach(cancelPageImageRequest)
+    }
+    
     func purgeAllViews() {
         pageViews.indices.forEach(purgePage)
     }