Show assets immediately after granting permissions

Tusker/Screens/Asset Picker/AssetCollectionViewController.swift

@@ -69,6 +69,7 @@ class AssetCollectionViewController: UICollectionViewController {
         navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(donePressed))
 
         collectionView.alwaysBounceVertical = true
+        collectionView.allowsMultipleSelection = true
         
         collectionView.register(UINib(nibName: "AssetCollectionViewCell", bundle: .main), forCellWithReuseIdentifier: reuseIdentifier)
         collectionView.register(UINib(nibName: "ShowCameraCollectionViewCell", bundle: .main), forCellWithReuseIdentifier: cameraReuseIdentifier)
@@ -97,19 +98,6 @@ class AssetCollectionViewController: UICollectionViewController {
             }
         })
         
-        let options = PHFetchOptions()
-        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
-        fetchResult = fetchAssets(with: options)
-        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
-        snapshot.appendSections([.assets])
-        var items: [Item] = [.showCamera]
-        fetchResult.enumerateObjects { (asset, _, _) in
-            items.append(.asset(asset))
-        }
-        snapshot.appendItems(items)
-        dataSource.apply(snapshot, animatingDifferences: false)
-        
-        collectionView.allowsMultipleSelection = true
         setEditing(true, animated: false)
         
         updateItemsSelectedCount()
@@ -122,6 +110,12 @@ class AssetCollectionViewController: UICollectionViewController {
         }
     }
     
+    override func viewWillAppear(_ animated: Bool) {
+        super.viewWillAppear(animated)
+        
+        loadAssets()
+    }
+    
     override func viewWillLayoutSubviews() {
         super.viewWillLayoutSubviews()
         
@@ -137,6 +131,40 @@ class AssetCollectionViewController: UICollectionViewController {
         }
     }
     
+    private func loadAssets() {
+        switch PHPhotoLibrary.authorizationStatus(for: .readWrite) {
+        case .notDetermined:
+            PHPhotoLibrary.requestAuthorization(for: .readWrite) { (_) in
+                self.loadAssets()
+            }
+            return
+            
+        case .restricted, .denied:
+            // todo: better UI for this
+            return
+            
+        case .authorized, .limited:
+            // todo: show "add more" button for limited access
+            break
+            
+        @unknown default:
+            // who knows, just try anyways
+            break
+        }
+        
+        let options = PHFetchOptions()
+        options.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
+        fetchResult = fetchAssets(with: options)
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        snapshot.appendSections([.assets])
+        var items: [Item] = [.showCamera]
+        fetchResult.enumerateObjects { (asset, _, _) in
+            items.append(.asset(asset))
+        }
+        snapshot.appendItems(items)
+        dataSource.apply(snapshot, animatingDifferences: false)
+    }
+    
     open func fetchAssets(with options: PHFetchOptions) -> PHFetchResult<PHAsset> {
         return PHAsset.fetchAssets(with: options)
     }