fix: ios is multithread. Ensure operations are run on the main thread

will also ensure things are done in the right order

Author: farfromrefug

src/collectionview.ios.ts

@@ -26,6 +26,7 @@ export * from './collectionview-common';
 const infinity = layout.makeMeasureSpec(0, layout.UNSPECIFIED);
 
 
+const main_queue = dispatch_get_current_queue();
 
 export enum ContentInsetAdjustmentBehavior {
     Always = UIScrollViewContentInsetAdjustmentBehavior.Always,
@@ -248,9 +249,11 @@ export class CollectionView extends CollectionViewBase {
                 if (Trace.isEnabled()) {
                     CLog(CLogTypes.info, 'deleteItemsAtIndexPaths', indexes.count);
                 }
-                view.performBatchUpdatesCompletion(() => {
-                    view.deleteItemsAtIndexPaths(indexes);
-                }, null);
+                dispatch_async(main_queue, () => {
+                    view.performBatchUpdatesCompletion(() => {
+                        view.deleteItemsAtIndexPaths(indexes);
+                    }, null);
+                });
                 return;
             }
             case ChangeType.Update: {
@@ -259,10 +262,12 @@ export class CollectionView extends CollectionViewBase {
                 if (Trace.isEnabled()) {
                     CLog(CLogTypes.info, 'reloadItemsAtIndexPaths',event.index, indexes.count);
                 }
-                UIView.performWithoutAnimation(()=>{
-                    view.performBatchUpdatesCompletion(() => {
-                        view.reloadItemsAtIndexPaths(indexes);
-                    }, null);
+                dispatch_async(main_queue, () => {
+                    UIView.performWithoutAnimation(()=>{
+                        view.performBatchUpdatesCompletion(() => {
+                            view.reloadItemsAtIndexPaths(indexes);
+                        }, null);
+                    });
                 });
 
                 return;
@@ -275,36 +280,39 @@ export class CollectionView extends CollectionViewBase {
                 if (Trace.isEnabled()) {
                     CLog(CLogTypes.info, 'insertItemsAtIndexPaths', indexes.count);
                 }
-                view.performBatchUpdatesCompletion(() => {
-                    view.insertItemsAtIndexPaths(indexes);
-                }, null);
+                dispatch_async(main_queue, () => {
+                    view.performBatchUpdatesCompletion(() => {
+                        view.insertItemsAtIndexPaths(indexes);
+                    }, null);
+                });
                 // Reload the items to avoid duplicate Load on Demand indicators:
                 return;
             }
             case ChangeType.Splice: {
-                view.performBatchUpdatesCompletion(() => {
-                    if (event.addedCount > 0) {
-                        const indexes = NSMutableArray.alloc<NSIndexPath>().init();
-                        for (let index = 0; index < event.addedCount; index++) {
-                            indexes.addObject(NSIndexPath.indexPathForItemInSection(event.index + index, 0));
-                        }
-                        view.insertItemsAtIndexPaths(indexes);
-                    }
-                    if (event.removed && event.removed.length > 0) {
-                        const indexes = NSMutableArray.new<NSIndexPath>();
-                        for (let index = 0; index < event.removed.length; index++) {
-                            indexes.addObject(NSIndexPath.indexPathForItemInSection(event.index + index, 0));
+                dispatch_async(main_queue, () => {
+                    view.performBatchUpdatesCompletion(() => {
+                        if (event.addedCount > 0) {
+                            const indexes = NSMutableArray.alloc<NSIndexPath>().init();
+                            for (let index = 0; index < event.addedCount; index++) {
+                                indexes.addObject(NSIndexPath.indexPathForItemInSection(event.index + index, 0));
+                            }
+                            view.insertItemsAtIndexPaths(indexes);
                         }
-                        this.unbindUnusedCells(event.removed);
-                        if (Trace.isEnabled()) {
-                            CLog(CLogTypes.info, 'deleteItemsAtIndexPaths', indexes.count);
+                        if (event.removed && event.removed.length > 0) {
+                            const indexes = NSMutableArray.new<NSIndexPath>();
+                            for (let index = 0; index < event.removed.length; index++) {
+                                indexes.addObject(NSIndexPath.indexPathForItemInSection(event.index + index, 0));
+                            }
+                            this.unbindUnusedCells(event.removed);
+                            if (Trace.isEnabled()) {
+                                CLog(CLogTypes.info, 'deleteItemsAtIndexPaths', indexes.count);
+                            }
+                            view.performBatchUpdatesCompletion(() => {
+                                view.deleteItemsAtIndexPaths(indexes);
+                            }, null);
                         }
-                        view.performBatchUpdatesCompletion(() => {
-                            view.deleteItemsAtIndexPaths(indexes);
-                        }, null);
-                    }
-                }, null);
-
+                    }, null);
+                });
                 return;
             }
         }
@@ -354,7 +362,9 @@ export class CollectionView extends CollectionViewBase {
 
         // TODO: this is ugly look here: https://github.com/nativescript-vue/nativescript-vue/issues/525
         // this.clearRealizedCells();
-        this.nativeViewProtected.reloadData();
+        dispatch_async(main_queue, () => {
+            this.nativeViewProtected.reloadData();
+        });
 
         const args = {
             eventName: CollectionViewBase.dataPopulatedEvent,
@@ -613,7 +623,7 @@ export class CollectionView extends CollectionViewBase {
     }
 
     collectionViewNumberOfItemsInSection(collectionView: UICollectionView, section: number) {
-        return this.items ? this.items.length : 0;
+        return this.items?.length || 0;
     }
 
     collectionViewCellForItemAtIndexPath(collectionView: UICollectionView, indexPath: NSIndexPath): UICollectionViewCell {