[ios, macos] Fix offline packs, updating triggers a crash.

platform/darwin/src/MGLOfflineStorage.h

@@ -139,10 +139,10 @@ typedef void (^MGLOfflinePackRemovalCompletionHandler)(NSError * _Nullable error
  
  @param fileURL The file URL of the offline database containing the offline packs
  that were copied.
- @param packs Contains an array of all known offline packs, or `nil` if there was
- an error creating or adding the pack.
- @param error Contains a pointer to an error object (if any) indicating why the
- pack could not be created or added.
+ @param packs An array of all known offline packs, or `nil` if there was an error
+ creating or adding the pack.
+ @param error A pointer to an error object (if any) indicating why the pack could
+ not be created or added.
  */
 typedef void (^MGLBatchedOfflinePackAdditionCompletionHandler)(NSURL *fileURL, NSArray<MGLOfflinePack *> * _Nullable packs, NSError * _Nullable error);
 
@@ -194,9 +194,6 @@ MGL_EXPORT
  The file must be a valid offline region database bundled with the application
  or downloaded separately.
  
- Refer to this <a href="https://www.mapbox.com/ios-sdk/maps/examples/offline-pack/">example</a>
- to learn how to download offline packs.
- 
  The resulting packs are added or updated to the shared offline storage object’s `packs`
  property, then the `completion` block is executed.
  
@@ -214,9 +211,6 @@ MGL_EXPORT
  The file must be a valid offline region database bundled with the application
  or downloaded separately.
  
- Refer to this <a href="https://www.mapbox.com/ios-sdk/maps/examples/offline-pack/">example</a>
- to learn how to download offline packs.
- 
  The resulting packs are added or updated to the shared offline storage object’s `packs`
  property, then the `completion` block is executed.
  

platform/darwin/src/MGLOfflineStorage.mm

@@ -296,19 +296,21 @@ - (void)addContentsOfURL:(NSURL *)fileURL withCompletionHandler:(MGLBatchedOffli
 
             id mutablePacks = [strongSelf mutableArrayValueForKey:@"packs"];
             NSMutableIndexSet *replaceIndexSet = [NSMutableIndexSet indexSet];
+            NSMutableArray *replacePacksArray = [NSMutableArray array];
             [strongSelf.packs enumerateObjectsUsingBlock:^(MGLOfflinePack * _Nonnull pack, NSUInteger idx, BOOL * _Nonnull stop) {
                 MGLOfflinePack *newPack = packsByIdentifier[@(pack.mbglOfflineRegion->getID())];
                 if (newPack) {
                     MGLOfflinePack *previousPack = [mutablePacks objectAtIndex:idx];
                     [previousPack invalidate];
                     [replaceIndexSet addIndex:idx];
+                    [replacePacksArray addObject:[packsByIdentifier objectForKey:@(newPack.mbglOfflineRegion->getID())]];
                     [packsByIdentifier removeObjectForKey:@(newPack.mbglOfflineRegion->getID())];
                 }
 
             }];
 
             if (replaceIndexSet.count > 0) {
-                [mutablePacks replaceObjectsAtIndexes:replaceIndexSet withObjects:packs];
+                [mutablePacks replaceObjectsAtIndexes:replaceIndexSet withObjects:replacePacksArray];
             }
 
             [mutablePacks addObjectsFromArray:packsByIdentifier.allValues];

platform/darwin/test/MGLOfflineStorageTests.mm

@@ -315,6 +315,11 @@ - (void)testAddFileContent {
 
         NSUInteger countOfPacks = [MGLOfflineStorage sharedOfflineStorage].packs.count;
 
+        [self keyValueObservingExpectationForObject:[MGLOfflineStorage sharedOfflineStorage] keyPath:@"packs" handler:^BOOL(id _Nonnull observedObject, NSDictionary * _Nonnull change) {
+            const auto changeKind = static_cast<NSKeyValueChange>([change[NSKeyValueChangeKindKey] unsignedLongValue]);
+            NSIndexSet *indices = change[NSKeyValueChangeIndexesKey];
+            return changeKind == NSKeyValueChangeInsertion && indices.count == 1;
+        }];
 
         XCTestExpectation *fileAdditionCompletionHandlerExpectation = [self expectationWithDescription:@"add database content completion handler"];
         MGLOfflineStorage *os = [MGLOfflineStorage sharedOfflineStorage];