Respond to CR.

Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift

@@ -241,12 +241,12 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
         isInBatchSelectMode = true
 
         for attachment in attachments {
-            guard let assetId = attachment.sourceId else {
+            guard let assetId = attachment.assetId else {
                 owsFailDebug("Attachment is missing asset id.")
                 continue
             }
             // Link the attachment with its asset to ensure caption continuity.
-            attachment.sourceId = assetId
+            attachment.assetId = assetId
             // Restore any existing caption for this attachment.
             attachment.captionText = assetIdToCommentMap[assetId]
         }
@@ -349,7 +349,6 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
         if isInBatchSelectMode {
             updateDoneButton()
         } else {
-            let asset = photoCollectionContents.asset(at: indexPath.row)
             complete(withAssets: [asset])
         }
     }
@@ -404,7 +403,7 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
     func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, changedCaptionOfAttachment attachment: SignalAttachment) {
         AssertIsOnMainThread()
 
-        guard let assetId = attachment.sourceId else {
+        guard let assetId = attachment.assetId else {
             owsFailDebug("Attachment missing source id.")
             return
         }

Signal/src/ViewControllers/PhotoLibrary/PhotoLibrary.swift

@@ -151,13 +151,13 @@ class PhotoCollectionContents {
         case .image:
             return requestImageDataSource(for: asset).map { (dataSource: DataSource, dataUTI: String) in
                 let attachment = SignalAttachment.attachment(dataSource: dataSource, dataUTI: dataUTI, imageQuality: .medium)
-                attachment.sourceId = asset.localIdentifier
+                attachment.assetId = asset.localIdentifier
                 return attachment
             }
         case .video:
             return requestVideoDataSource(for: asset).map { (dataSource: DataSource, dataUTI: String) in
                 let attachment = SignalAttachment.attachment(dataSource: dataSource, dataUTI: dataUTI)
-                attachment.sourceId = asset.localIdentifier
+                attachment.assetId = asset.localIdentifier
                 return attachment
             }
         default:

SignalMessaging/attachments/SignalAttachment.swift

@@ -160,9 +160,9 @@ public class SignalAttachment: NSObject {
     @objc
     public let dataUTI: String
 
-    // Can be used by views to link this SignalAttachment with an arbitrary source.
+    // Can be used by views to link this SignalAttachment with an Photos framework asset.
     @objc
-    public var sourceId: String?
+    public var assetId: String?
 
     var error: SignalAttachmentError? {
         didSet {