Changed PrefetchViewModel init with params to init()

Use load(...) functions instead now.
nenosinc · Apr 17, 2021 · 61e78ba · 61e78ba
1 parent 72ad00b
commit 61e78ba
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Showing 2 changed files with 35 additions and 13 deletions.
diff --git a/Source/PrefetchImageModel.swift b/Source/PrefetchImageModel.swift
@@ -14,38 +14,60 @@ public final class PrefetchViewModel: ObservableObject, ScrollViewPrefetcherDele
     private let scrollViewPrefetcer: ScrollViewPrefetcher
     public private(set) var urls: [URL]
 
-    public init(photoURLs: [URL]) {
-        self.imagePrefetcher = ImagePrefetcher()
-        self.scrollViewPrefetcer = ScrollViewPrefetcher()
-        self.urls = photoURLs
-
-        self.scrollViewPrefetcer.delegate = self
+    public init() {
+        imagePrefetcher = ImagePrefetcher()
+        scrollViewPrefetcer = ScrollViewPrefetcher()
+        urls = []
+        scrollViewPrefetcer.delegate = self
+    }
+
+    public func load(photoURLs: [URL]) {
+        urls = photoURLs
+        scrollViewPrefetcer.scheduleRefreshIfNeeded()
     }
 
-    public init(photoReferences: [StorageReference], uniqueURL: @escaping (StorageReference) -> URL?) {
-        self.imagePrefetcher = ImagePrefetcher()
-        self.scrollViewPrefetcer = ScrollViewPrefetcher()
-        self.urls = []
-        self.scrollViewPrefetcer.delegate = self
+    public func load(photoReferences: [StorageReference], uniqueURL: @escaping (StorageReference) -> URL?) {
+        let loadTask = DispatchGroup()
+        let totalRefs = photoReferences.count
+        var currentRef: Int = 1
 
         for ref in photoReferences {
+            if currentRef == 1 {
+                loadTask.enter()
+            }
+
             if let cachedURL = uniqueURL(ref) {
-                self.urls.append(cachedURL)
+                urls.append(cachedURL)
+
+                currentRef = currentRef + 1
+                if currentRef >= totalRefs {
+                    loadTask.leave()
+                }
                 continue
             } else {
                 DispatchQueue.global(qos: .userInitiated).async {
                     ref.downloadURL { (foundURL, thrownError) in
                         if let safeFoundURL = foundURL {
                             self.urls.append(safeFoundURL)
+                            currentRef = currentRef + 1
                         } else {
                             if let safeError = thrownError {
                                 print("[PrefetchViewModel] Unable to fetch download URL for photo. \(safeError)")
+                                currentRef = currentRef + 1
                             }
                         }
+
+                        if currentRef >= totalRefs {
+                            loadTask.leave()
+                        }
                     }
                 }
             }
         }
+
+        loadTask.notify(queue: DispatchQueue.main) {
+            self.scrollViewPrefetcer.scheduleRefreshIfNeeded()
+        }
     }
 
     func onAppear(_ index: Int) {

diff --git a/Source/ScrollViewPrefetcher.swift b/Source/ScrollViewPrefetcher.swift
@@ -43,7 +43,7 @@ public final class ScrollViewPrefetcher {
 
     /// SwiftUI sometimes calls onAppear in unexpected order, buffer takes care of it.
     ///
-    private func scheduleRefreshIfNeeded() {
+    internal func scheduleRefreshIfNeeded() {
         guard !isRefreshScheduled else { return }
         isRefreshScheduled = true
         DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) { [weak self] in