#TABLE SWIPE DELETE FLICKERY SWIFT HOW TO#
#TABLE SWIPE DELETE FLICKERY SWIFT UPDATE#
#TABLE SWIPE DELETE FLICKERY SWIFT PLUS#

That is to call reloadItems outside the performBatchUpdates. There’s one thing to notice, otherwise you will get the familiar ‘ NSInternalInconsistencyException’. You can take a look at UICollectionView extension. The conversion from Change to IndexPath is pretty much self explanatory. With the changes array returned by DeepDiff, we can infer the required set of IndexPath to feed to UICollectionView to perform the updates. You can take a look at the MoveReducer, it’s not very efficiently implemented, but at least it gives you some hints. A move is just a deletion following by insertion of the same item. Where’s the move? Turn out that’s it’s not difficult.

The algorithms have some other little details, but you should take a look at the code, it tells you more.īy now you have notice we have just updated steps for insertions, deletions and replacement. Since each kind of Change is mutual exclusive, they are perfect to be represented as enum Seeing that we only operate one row at a time, it’s inefficient to store the whole matrix, instead we can just use 2 arrays to compute, and that also reduces the memory footprint. “We can adapt the algorithm to use less space, O(m) instead of O(mn), since it only requires that the previous row and current row be stored at any one time.” If you take a look at the wiki page, there’s some hints on what we can do to improve performance. The more complex and how deep you want to perform Equatable can greatly affect your performance. So we can see that the complexity of this algorithm is O(mn).Īlso the performance greatly depends on the size of the collection and how complex the item is. We iterate through the matrix, where m and n are the length of source and destination collection respectively. But in the next sections, I will outline some technical points in the library for you to easily follow.

#TABLE SWIPE DELETE FLICKERY SWIFT UPDATE#

With a collection of 6 items, we perform some update operations and figure out what IndexPath should be.įor a better understanding, take a look at more examples here: CollectionUpdateExample.Ĭode is the ultimate source of explanation. Let’s refine our knowledge of IndexPath by going through some examples. Although the message is very descriptive, it may take a while to figure it out. In my experience it happened randomly because user has different data.

#TABLE SWIPE DELETE FLICKERY SWIFT PLUS#

The number of items contained in an existing section after the update (213) must be equal to the number of items contained in that section before the update (154), plus or minus the number of items inserted or deleted from that section (40 inserted, 0 deleted) and plus or minus the number of items moved into or out of that section (0 moved in, 0 moved out).’ Terminating app due to uncaught exception ‘NSInternalInconsistencyException’, reason: ‘Invalid update: invalid number of items in section 0. Most the time you will get the following crashes: If you have a large number of items with many insertions and deletions from backend response, you need to calculate the correct IndexPath to call, which are not an easy thing. But in real projects, the data is much more complex, the changes are not that trivial. This is a trivial example, you just remove or add 1 item from a collection. And to any of you searching for NSCollectionView on Google, it is just a bit harder: This guide uses UICollectionView as examples, but UITableView behaves the same.

#TABLE SWIPE DELETE FLICKERY SWIFT HOW TO#

Unfortunately, you don’t have that luxury in iOS, but we can learn how to do it. If you’re doing Android, you probably know that instead of calling notifyDataSetChanged, you can use the provided DiffUtil to calculate the changes for us, so that updating RecyclerView becomes easy. Further if those changes should be noticeable, and you want to give users better understanding of what’s going on, then manually insert and delete of rows is preferred. But it makes the UITableView reinvalidate cell sizes again, which can reduce performance. It’s fine for scenarios when you want a quick way to refresh content. This way the whole list is refreshed with completely new content.

That’s where your favorite function comes in, reloadData. And later, when data has changed, we update your interface to reflect that some items have been inserted or deleted. Most of the time, we fetch data from the backend, cache and filter to show that data as list or grid. It’s hard to imagine any apps that don’t use table view or collection view, via classes like UITableView, UICollectionView in iOS, tvOS or NSTableView, NSCollectionView in macOS.

Table swipe delete flickery swift