# CHANGELOG

The changelog for `IGListKit`. Also see the [releases](https://github.com/instagram/IGListKit/releases) on GitHub.


5.0.0 (upcoming release)
-----

### Breaking Changes

- Removed unneeded diffing functions `IGListDiffExperiment(...)` and `IGListDiffPathsExperiment(...)`. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- `ListSectionController.collectionContext` and `ListGenericSectionController.object` are now implicitly-unwrapped optionals in Swift. [Nate Stedman](https://github.com/natestedman) (tbd)

- The argument of `IGListGenericSectionController`'s `-didUpdateToObject:` is now generic, not `id`. [Nate Stedman](https://github.com/natestedman) (tbd)

- Updated  `IGListUpdatingDelegate`, including a new method to safely perform `[IGListAdapter setDataSource:]` and changes to `-performUpdateWithCollectionViewBlock` that allows section-controllers to be created before the diffing (and therefore use a more accurate `toObjects` array) [Maxime Ollivier](https://github.com/maxolls) (tbd)

```objc
// OLD
- (void)performUpdateWithCollectionViewBlock:(IGListCollectionViewBlock)collectionViewBlock
                                 fromObjects:(nullable NSArray<id <IGListDiffable>> *)fromObjects
                              toObjectsBlock:(nullable IGListToObjectBlock)toObjectsBlock
                                    animated:(BOOL)animated
                       objectTransitionBlock:(IGListObjectTransitionBlock)objectTransitionBlock
                                  completion:(nullable IGListUpdatingCompletion)completion;

// NEW
- (void)performUpdateWithCollectionViewBlock:(IGListCollectionViewBlock)collectionViewBlock
                                    animated:(BOOL)animated
                            sectionDataBlock:(IGListTransitionDataBlock)sectionDataBlock
                       applySectionDataBlock:(IGListTransitionDataApplyBlock)applySectionDataBlock
                                  completion:(nullable IGListUpdatingCompletion)completion;

// NEW
- (void)performDataSourceChange:(IGListDataSourceChangeBlock)block;
```

- Removed `allowsBackgroundReloading` from `IGListAdapterUpdater` because it's causing performance issues and other bugs. [Maxime Ollivier](https://github.com/maxolls) (tbd)

### Enhancements

- Added `shouldSelectItemAtIndex:` to `IGListSectionController` . [dirtmelon](https://github.com/dirtmelon)

- Introduce `IGListSwiftKit`, with Swift refinements for `dequeueReusableCellOfClass` methods. [Koen Punt](https://github.com/koenpunt) [(#1388)](https://github.com/Instagram/IGListKit/pull/1388).

- Added `APPLICATION_EXTENSION_API_ONLY` support for `IGListDiffKit` [Peter Meyers](https://github.com/pm-dev) [(#1422)](https://github.com/Instagram/IGListKit/pull/1422)

-  Improved performance by deferring requesting objects from the `IGListAdapterDataSource` until just before diffing is executed. If n updates are coalesced into one, this results in just a single request for objects from the data source. Shipped with experiment `IGListExperimentDeferredToObjectCreation` from Ryan Nystrom.  [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Improved performance by using `reloadData` when there are too many diffing updates. Shipped with experiment `IGListExperimentReloadDataFallback` from Ryan Nystrom. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Small performance improvement by replacing `NSSet` with `NSArray` during the data update to avoid unnecessary hashing, especially when dealing with lots of large objects with non trivial hashes. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Lazy initialize the `-emptyViewForListAdapter:` [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Updated  `IGListAdapterUpdater` to be safer, more performant, and better organized! [Maxime Ollivier](https://github.com/maxolls) (tbd)
   - Safely handles `[IGListAdapter setDataSource:]` by also invalidating the `UICollectionView` data.
   - Safely handles `[IGListAdapter setCollectionView:]` by cancelling on-going transactions.
   - Safely handles returning nil `IGListSectionController` from `IGListAdapterDataSource` by dumping objects that don't have a controller before the diffing.
   - Checks that the `UICollectionView` section count matches the `IGListAdapter` before committing the update, otherwise fallback to a reload.
   - Schedules an update block (`dispatch_async`) only when needed, instead of scheduling on every single call to `-performUpdateWithCollectionViewBlock`.
   - Wraps each update in a `transaction` that can be easily cancelled.
   - Uses methods instead of blocks to make the callstack easier to read in crash reports.
   - Unblocks `IGListExperimentBackgroundDiffing` 

### Fixes

- `IGListCollectionViewLayout` should get the section/index counts via `UICollectionView` to stay in sync, instead of the `dataSource` [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Remove `[collectionView layoutIfNeeded]` before scrolling in `[IGListAdapter scrollToObject...]` to avoid creating off-screen cells. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Remove `[collectionView layoutIfNeeded]` before updating in `[IGListAdapterUpdater performBatchUpdates...]` to fix occasional glitches. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Fixed `IGListAdapterUpdaterDelegate` by 1) calling `willReloadDataWithCollectionView` on fallback reloads and 2) making sure `willPerformBatchUpdatesWithCollectionView` is only called when performing a batch update. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Fixed missing update when calling `performUpdatesAnimated` multiple times quickly and using the `reloadDataFallback()`. [Maxime Ollivier](https://github.com/maxolls) (tbd)

- Request the `UICollectionView` until just-before we update. This way if the `UICollectionView` is changed between update-queue and execution, we guarantee the update is performed on the correct view. Ship with experiment `IGListExperimentGetCollectionViewAtUpdate` from Ryan Nystrom. [Maxime Ollivier](https://github.com/maxolls) (tbd)

4.0.0
-----
### Breaking Changes

- Added Swift annotation name to `IGListAdapterDelegate` which removes `IG` prefix. The new name for Swift clients is `ListAdapterDelegate`. [Andrea Antonioni](https://github.com/andreaantonioni) [(#1116)](https://github.com/Instagram/IGListKit/pull/1116)

- Remove support for iOS 8 [Ian Perry](https://github.com/iperry90) [(#1381)](https://github.com/Instagram/IGListKit/pull/1381)

- `IGListKit` has been split into `IGListKit` and `IGListDiffKit` for Xcode and Carthage builds. Cocoapods continues to use an all-inclusive `IGListKit` podspec. [Nate Stedman](https://github.com/natestedman) [(#1377)](https://github.com/Instagram/IGListKit/pull/1377)

- Remove `coalescanceTime` from IGListAdapterUpdate, since it increase crash rate. [Zhisheng Huang](https://github.com/lorixx) [(2f76e8c)](https://github.com/Instagram/IGListKit/commit/2f76e8ce684bf7cea75ee52f25d4ea0af3e0081b)

- All `IGListBindingSectionControllerSelectionDelegate` methods are now required. [Bofei Zhu](https://github.com/zhubofei) [(#1186)](https://github.com/Instagram/IGListKit/pull/1186)

- Renamed `[IGListAdapterUpdatingDelegate listAdapterUpdater:willPerformBatchUpdatesWithCollectionView:]` to `[IGListAdapterUpdatingDelegate listAdapterUpdater:willPerformBatchUpdatesWithCollectionView:fromObjects:toObjects:listIndexSetResult:]` to include more supporting info on updated objects. [Jeremy Cohen](https://github.com/jeremycohen) [(b200dda)](https://github.com/Instagram/IGListKit/commit/b200ddacf59547641d77e31d313566c78944a67b)

- Renamed `[IGListAdapterUpdatingDelegatelistAdapterUpdater:collectionView:willCrashWithException:fromObjects:toObjects:updates:]` to `[ IGListAdapterUpdatingDelegatelistAdapterUpdater:collectionView:willCrashWithException:fromObjects:toObjects:diffResult:updates:]` to include diff result info. [Zhisheng Huang](https://github.com/lorixx) [(039e77e)](https://github.com/Instagram/IGListKit/commit/039e77e3593251c8711497f76ab25857d641ecee)

- Remove `IGListStackedSectionController`. [Hanton Yang](https://github.com/hanton) [(#1355)](https://github.com/Instagram/IGListKit/pull/1355)

### Enhancements

- Added `IGListCollectionScrollingTraits` for exposing `UICollectionView` scrolling traits to section controllers via `IGListCollectionContext`. [Adam Stern](https://github.com/adamastern) [(b4c8ea1)](https://github.com/Instagram/IGListKit/commit/b4c8ea180f3bbda8b7995da758fbec58bf7214a8)

-  `IGListBindingSectionController` no longer asserts when reloading the entire section. A warning message is now logged if the entire section is going to be reloaded. [Jeff Bailey](https://github.com/jeffbailey) [(#1213)](https://github.com/Instagram/IGListKit/pull/1213)

- Added `preferItemReloadsForSectionReloads` in IGListAdapterUpdater so that the item updates are invoked with the proper collectionView animation, instead of using the delete+insert section operation when the number of items is unchanged. [Zhisheng Huang](https://github.com/lorixx) [(f699ea0)](https://github.com/Instagram/IGListKit/commit/f699ea0e17a8cc6335285dc9f86fb80a0ad49700)

- Created `IGListAdapterPerformanceDelegate` for IGListAdapter to be able to measure how long some operations take across all section controllers. For example, how long it takes to dequeue a cell. [Maxime Ollivier](https://github.com/maxoll) [(4662454)](https://github.com/Instagram/IGListKit/commit/4662454c4aedbc5d3bed0cb386f2ef93de40ba51)

- Update CocoaPods integration to use the CocoaPods specs CDN [Koen Punt](https://github.com/koenpunt) [(#1386)](https://github.com/Instagram/IGListKit/pull/1386)

- Remove useless system version code [Kinarobin](https://github.com/kinarobin) [(#1386)](https://github.com/Instagram/IGListKit/pull/1396)

### Fixes

- Fixed bug with layouts inconsistency in `updateAnimated:completion` of IGListBindingSectionController. [Qinghua Hong](https://github.com/qhhonx) [(#1285)](https://github.com/Instagram/IGListKit/pull/1285)

- Fixed bug with `-[IGListAdapter scrollToObject:supplementaryKinds:scrollDirection:scrollPosition:animated:]` where the content inset(bottom/right) of the collection view was incorrectly being applied to the final offset and was inconsistent with the content inset(top/left) of the collection view being applied. [Qinghua Hong](https://github.com/qhhonx) [(#1284)](https://github.com/Instagram/IGListKit/pull/1284)

- Fixed crash when the data source is nil before calling `-[IGListAdapterUpdater performUpdateWithCollectionViewBlock:fromObjects:toObjectsBlock:animated:objectTransitionBlock:completion:]`. [Zhisheng Huang](https://github.com/lorixx) [(6cdd112)](https://github.com/Instagram/IGListKit/commit/6cdd112790f13a683d3e061a7646f2c3549cc4dd)

- Experimental fix to get the `UICollectionView` for batch updating immediately before applying the update. [Ryan Nystrom](https://github.com/rnystrom) [(583efb9)](https://github.com/Instagram/IGListKit/commit/583efb936b0ba4d8beac0678b145aa5aff8ac12b)

- Fixed bug with `IGListDiff.mm` where arrays of `NSIndexPath`, instead of `NSIndexPath`, were incorrectly set as objects for the IndexPathMaps. [Bofei Zhu](https://github.com/zhubofei) [(#1205)](https://github.com/Instagram/IGListKit/pull/1205)

- `[IGListAdapterUpdater performBatchUpdatesWithCollectionViewBlock:]` and `[IGListAdapterUpdater performReloadDataWithCollectionViewBlock:]` clean state and run completion blocks if their `UICollectionView` is nil. [Brandon Darin](https://github.com/jbd1030) [(290d592)](https://github.com/Instagram/IGListKit/commit/290d592983713c3ef82eb4950ba773a0059563a2)

- Ensuring view models with duplicate diff identifiers are removed when view models are first requested by `IGListBindingSectionController` [Adam Stern](https://github.com/adamastern) [(a1ee4c1)](https://github.com/Instagram/IGListKit/commit/a1ee4c19f7a6cbd9899dba82deb5fb3ece669e9c)

- Fixed `[IGListAdapterUpdater reloadItemInCollectionView:fromIndexPath:toIndexPath:]` does not call delegate when not inside a batch update. [Bofei Zhu](https://github.com/zhubofei) [(#1211)](https://github.com/Instagram/IGListKit/pull/1211)

- Log instead of assert for duplicate diff identifiers to make code testable. [Adam Stern](https://github.com/adamastern) [(bee2178)](https://github.com/Instagram/IGListKit/commit/bee2178443ffcaff1d9135c4e094f74240433a62)

- Removed `nibName` argument from `IGListReusableViewIdentifier`. [Trung Duc](https://github.com/trungducc) [(#1223)](https://github.com/Instagram/IGListKit/issues/1223)

- Fixed crash when using `-[IGListCollectionContext dequeueReusableCellOfClass:withReuseIdentifier:forSectionController:atIndex:]` [Jeremy Lawrence](https://github.com/ziewvater) [(3b19cfb)](https://github.com/Instagram/IGListKit/commit/3b19cfb9d742d1fd97540bd8cf42c3552ab47de9)

- Added missing method override to `IGListBindingSectionController` that updates the internal `viewModels` array after moving a cell. [Dennis Müller](https://github.com/d3mueller) [(#1262)](https://github.com/Instagram/IGListKit/issues/1262)

- Fixed logic flaw in `[IGListCollectionViewLayout shouldInvalidateLayoutForBoundsChange:]`. [Allen Hsu](https://github.com/allenhsu) [(#1236)](https://github.com/Instagram/IGListKit/pull/1236)

- Fixed crash when calling `[UICollectionView layoutAttributesForSupplementaryElementOfKind...]` with `IGListCollectionViewLayout` and the section controller doesn't actually return a supplementary view [Maxime Ollivier](https://github.com/maxolls) [(cddb297)](https://github.com/Instagram/IGListKit/commit/cddb29799c5393f3c1a1ab7e9c072208e8c23225)

- Added `IGListExperimentAvoidLayoutOnScrollToObject` to avoid creating off-screen cells when calling `[IGListAdapter scrollToObject ...]`. [Maxime Ollivier](https://github.com/maxolls) [(6faddd9)](https://github.com/Instagram/IGListKit/commit/6faddd99c95428cf42bb38684464b458ef1455c0)

- Added `IGListExperimentFixIndexPathImbalance` to test fixing a crash when inserting and deleting the same NSIndexPath multiple times. [Maxime Ollivier](https://github.com/maxolls) [(7824698)](https://github.com/Instagram/IGListKit/commit/78246986108e7caf73111fe784057cc107ee67f1)

3.4.0
-----

### Enhancements

- Relicensed IGListKit to MIT. [Ryan Nystrom](https://github.com/rnystrom) [(000bc36)](https://github.com/Instagram/IGListKit/commit/000bc3691909f50649a5dfb098a5f2102c86385b)

- Experimental performance improvement from deferring `-[IGListAdapterDataSource objectsForListAdapter:]` calls until just before diffing. [Ryan Nystrom](https://github.com/rnystrom) [(3059c5e)](https://github.com/Instagram/IGListKit/commit/3059c5e6f5aeac73f112375d032677ae5f38342a)

3.3.0
-----

### Enhancements

- Add support for UICollectionView's interactive reordering in iOS 9+.  Updates include `-[IGListSectionController canMoveItemAtIndex:]` to enable the behavior, `-[IGListSectionController moveObjectFromIndex:toIndex:]` called when items within a section controller were moved through reordering, `-[IGListAdapterDataSource listAdapter:moveObject:from:to]` called when section controllers themselves were reordered (only possible when all section controllers contain exactly 1 object), and `-[IGListUpdatingDelegate moveSectionInCollectionView:fromIndex:toIndex]` to enable custom updaters to conform to the reordering behavior. The update also includes two new examples `ReorderableSectionController` and `ReorderableStackedViewController` to demonstrate how to enable interactive reordering in your client app. [Jared Verdi](https://github.com/jverdi) [(#976)](https://github.com/Instagram/IGListKit/pull/976)

- 5x improvement to diffing performance when result is only inserts or deletes. [Ryan Nystrom](https://github.com/rnystrom) [(afd2d29)](https://github.com/Instagram/IGListKit/commit/afd2d29eecfac2231d2bcf815c76e844c98d838e)

- Can always show sticky header although section data is empty.  [Marcus Wu](https://github.com/marcuswu0814) [(#1129)](https://github.com/Instagram/IGListKit/pull/1129)

- Added `-[IGListCollectionContext dequeueReusableCellOfClass:withReuseIdentifier:forSectionController:atIndex:]` to allow for registering cells of the same class with different reuse identifiers. [Jeremy Lawrence](https://github.com/Ziewvater) [(f47753e)](https://github.com/Instagram/IGListKit/commit/f47753e3615431f3b079eb3b7900469f9ffdce5b)

### Fixes

- Fixed Xcode 9.3 build errors. [Sho Ikeda](https://github.com/ikesyo) [(#1143)](https://github.com/Instagram/IGListKit/pull/1143)

- Copy objects when retrieving from datasource to prevent modification of models in binding section controller. [Kashish Goel](https://github.com/kashishgoel) [(#1109)](https://github.com/Instagram/IGListKit/pull/1109)

- Fixed footer is sticky when `stickyHeader` is `true` [aelam](https://github.com/aelam) [(#1094)](https://github.com/Instagram/IGListKit/pull/1094)

- Updated IGListCollectionViewLayout to rely on layoutAttributesClass instead of vanilla `UICollectionViewLayoutAttributes` [Cole Potrocky](https://github.com/SirensOfTitan) [#1135](https://github.com/instagram/IGListKit/pull/1135)

- `-[IGListSectionController didSelectItemAtIndex:]` is now called when a `scrollViewDelegate` or `collectionViewDelegate` is set. [Ryan Nystrom](https://github.com/rnystrom) [(#1108)](https://github.com/Instagram/IGListKit/pull/1108)

- Fixed binding section controllers failing to update their cells when the section controller's section changes. [Chrisna Aing](https://github.com/ccrazy88) [(#1144)](https://github.com/Instagram/IGListKit/pull/1144)

- Fixed a bug caused when applying interactive reordering on a single section item while dragging it through the last spot of the collection view and back to some (non-last) target position. [Ofir Gluzman](https://github.com/ofirgluzman) [#1289](https://github.com/Instagram/IGListKit/pull/1289)

3.2.0
-----

### Enhancements

- Added `-[IGListSectionController didHighlightItemAtIndex:]` and `-[IGListSectionController didUnhighlightItemAtIndex:]` APIs to support `UICollectionView` cell highlighting. [Kevin Delannoy](https://github.com/delannoyk) [(#933)](https://github.com/Instagram/IGListKit/pull/933)

- Added `-didDeselectSectionController:withObject:` to `IGListSingleSectionControllerDelegate` [Darren Clark](https://github.com/darrenclark) [(#954)](https://github.com/Instagram/IGListKit/pull/954)

- Added a new listener API to be notified when `IGListAdapter` finishes updating. Add listeners via `-[IGListAdapter addUpdateListener:]` with objects conforming to the new `IGListAdapterUpdateListener` protocol. [Ryan Nystrom](https://github.com/rnystrom) [(5cf01cc)](https://github.com/Instagram/IGListKit/commit/5cf01cc0a7c41d370600df495aff91d1099fa0bc)

- Updated project settings for iOS 11. [Ryan Nystrom](https://github.com/rnystrom) [(#942)](https://github.com/Instagram/IGListKit/pull/942)

- Added support UICollectionElementKindSectionFooter for IGListCollectionViewLayout. [Igor Vasilenko](https://github.com/vasilenkoigor) [(#1017)](https://github.com/Instagram/IGListKit/pull/1017)

- Added experiment to make  `-[IGListAdapter visibleSectionControllers:]` a bit faster. [Maxime Ollivier](https://github.com/maxoll) [(82a2a2e)](https://github.com/Instagram/IGListKit/commit/82a2a2ee18bb6272744fd14c64c8ff2da3a620a6)

- Added support `-[UIScrollView adjustedContentInset]` for iOS 11. [Guoyin Li](https://github.com/yiplee) [(#1020)](https://github.com/Instagram/IGListKit/pull/1020)

- Added new `transitionDelegate` API to give `IGListSectionController`s control to customize initial and final `UICollectionViewLayoutAttribute`s. Includes automatic integration with `IGListCollectionViewLayout`. Sue Suhan Ma [(26924ec)](https://github.com/Instagram/IGListKit/commit/26924ec3b665d37aeed7e28887e4221a7f3501b1)

- Reordered position of intercepted selector in `IGListAdapterProxy`'s `isInterceptedSelector` method to reduce overall consumption of compare. [zhongwuzw](https://github.com/zhongwu) [(#1055)](https://github.com/Instagram/IGListKit/pull/1055)

- Made IGListTransitionDelegate inherited from NSObject. [Igor Vasilenko](https://github.com/vasilenkoigor) [(#1075)](https://github.com/Instagram/IGListKit/pull/1075)

### Fixes

- Duplicate objects for initial data source setup filtered out. [Mikhail Vashlyaev](https://github.com/yemodin) [(#993](https://github.com/Instagram/IGListKit/pull/993)

- Weakly reference the `UICollectionView` in coalescence so that it can be released if the rest of system is destroyed. [Ryan Nystrom](https://github.com/rnystrom) [(d322c2e)](https://github.com/Instagram/IGListKit/commit/d322c2e5ae241141309923da257542f163c07cc6)

- Fix bug with `-[IGListAdapter scrollToObject:supplementaryKinds:scrollDirection:scrollPosition:animated:]` where the content inset of the collection view was incorrectly being applied to the final offset. [Ryan Nystrom](https://github.com/rnystrom) [(b2860c3)](https://github.com/Instagram/IGListKit/commit/b2860c3604f0c452be1d21ab09c771c921786150)

- Avoid crash when invalidating the layout while inside `-[UICollectionView performBatchUpdates:completion:]. [Ryan Nystrom](https://github.com/rnystrom) [(d9a89c9)](https://github.com/Instagram/IGListKit/commit/d9a89c9b00aa1a9537a24d9affb6919f83065f65)

- Duplicate view models in `IGListBindingSectionController` gets filtered out. [Weyert de Boer](https://github.com/weyert) [(#916)](https://github.com/Instagram/IGListKit/pull/916)

- Check object type on lookup to prevent crossing types if different objects collide with their identifiers. [Ryan Nystrom](https://github.com/rnystrom) [(296baf5)](https://github.com/Instagram/IGListKit/commit/296baf5f854f57150ed12ca5bd8d3903db492734)

3.1.1
-----

### Fixes

- Prevent a crash when `IGListBindingSectionControllerDelegate` objects do not implement the optional deselection API. [Ryan Nystrom](https://github.com/rnystrom) [(#921)](https://github.com/Instagram/IGListKit/pull/921)

3.1.0
-----

### Enhancements

- Added debug descriptions for 'IGListBindingSectionController' when printing to lldb via `po [IGListDebugger dump]`. [Candance Smith](https://github.com/candance) [(#856)](https://github.com/Instagram/IGListKit/pull/856)

- Added `-[IGListSectionController didDeselectItemAtIndex:]` API to support default `UICollectionView` cell deselection. [Ryan Nystrom](https://github.com/rnystrom) [(6540f96)](https://github.com/Instagram/IGListKit/commit/6540f960e2e69bd4776e1e1d8c460ff812ba4c07)

- Added `-[IGListCollectionContext selectItemAtIndex:]` Select an item through IGListCollectionContext like `-[IGListCollectionContext deselectItemAtIndex:]`. [Marvin Nazari](https://github.com/MarvinNazari) [(#874)](https://github.com/Instagram/IGListKit/pull/874)

- Added horizontal scrolling support to `IGListCollectionViewLayout`. [Peter Edmonston](https://github.com/edmonston)  [(#857)](https://github.com/Instagram/IGListKit/pull/857)

- Added support for `scrollViewDidEndDecelerating` to `IGListAdapter`. [Phil Larson](https://github.com/plarson) [(#899)](https://github.com/Instagram/IGListKit/pull/899)

- Automatically disable `[UICollectionView isPrefetchingEnabled]` when setting a collection view on an adapter. [Ryan Nystrom](https://github.com/rnystrom) [(#889)](https://github.com/Instagram/IGListKit/pull/889)

### Fixes

- Prevent a crash when update queued immediately after item batch update. [Ryan Nystrom](https://github.com/rnystrom) [(3dc6060)](https://github.com/Instagram/IGListKit/commit/3dc6060a385d9bfcb4fa1f61262ba74776573229)

- Return correct `-[IGListAdapter visibleSectionControllers]` when section has no items, but has supplementary views. [Mani Ghasemlou](https://github.com/manicakes) [(#643)](https://github.com/Instagram/IGListKit/issues/643)

- Call `[CATransaction commit]` before calling completion block in IGListAdapterUpdater to prevent animation issues. [Maxime Ollivier](https://github.com/maxoll) [(6f946b2)](https://github.com/Instagram/IGListKit/commit/6f946b2981d266f823324a366213bd214357bb6d)

- Fix `scrollToObject:supplementaryKinds:...` not scrolling when section is empty but does have supplymentary views. [Gulam Moledina](https://github.com/gmoledina) [(#808)](https://github.com/Instagram/IGListKit/pull/808)

- Better support for non-top positions in `scrollToObject:` API. [Gulam Moledina](https://github.com/gmoledina) [(#861)](https://github.com/Instagram/IGListKit/pull/861)

3.0.0
-----

This release closes the [3.0.0 milestone](https://github.com/Instagram/IGListKit/milestone/3).

### Breaking Changes

- Added Swift annotation names which remove `IG` prefixes from class names, C functions, and other APIs. Note, this only affects Swift clients. [Robert Payne](https://github.com/robertjpayne) [(#593)](https://github.com/Instagram/IGListKit/pull/593)

Example:

```swift
// OLD
class MySectionController : IGListSectionController { ... }

// NEW
class MySectionController : ListSectionController { ... }

// OLD
IGListDiff([], [], .equality)

// NEW
ListDiff(oldArray: [], newArray: [], .equality)

```

- Updated `didSelect` delegate call in `IGListSingleSectionControllerDelegate` to include object. [Sherlouk](https://github.com/Sherlouk) [(#397)](https://github.com/Instagram/IGListKit/pull/397)

```objc
// OLD
- (void)didSelectSingleSectionController:(IGListSingleSectionController *)sectionController;

// NEW
- (void)didSelectSectionController:(IGListSingleSectionController *)sectionController
                        withObject:(id)object;
```

- `IGListUpdatingDelegate` now conforms to `NSObject`, bringing it in line with other framework protocols. [Adlai Holler](https://github.com/Adlai-Holler) [(#435)](https://github.com/Instagram/IGListKit/pull/435)

- Changed `hasChanges` methods in `IGListIndexPathResult` and `IGListIndexSetResult` to read-only properties. [Bofei Zhu](https://github.com/zhubofei) [(#453)](https://github.com/Instagram/IGListKit/pull/453)

- Replaced `IGListGridCollectionViewLayout` with `IGListCollectionViewLayout`. [Ryan Nystrom](https://github.com/rnystrom) ([#482](https://github.com/Instagram/IGListKit/pull/482), [#450](https://github.com/Instagram/IGListKit/pull/450))

- Renamed `IGListAdapterUpdaterDelegate` method to `listAdapterUpdater:didPerformBatchUpdates:collectionView:`. [Vincent Peng](https://github.com/vincent-peng) [(#491)](https://github.com/Instagram/IGListKit/pull/491)

- Moved section controller mutations to `IGListBatchContext`, provided as a parameter when calling `-performBatchAnimated:updates:completion` on a section controller's `collectionContext`. All updates (insert, delete, reload item/section controller) must now be done inside a batch update block. [Ryan Nystrom](https://github.com/rnystrom) [(a15ea08)](https://github.com/Instagram/IGListKit/commit/a15ea0861492c8476bc9b1b92b0d9835814091c7)

```objc
// OLD
[self.collectionContext performBatchAnimated:YES updates:^{
  self.expanded = YES;
  [self.collectionContext insertInSectionController:self atIndexes:[NSIndexSet indexSetWithIndex:1]];
} completion:nil];

// NEW
[self.collectionContext performBatchAnimated:YES updates:^(id<IGListBatchContext> batchContext) {
  self.expanded = YES;
  [batchContext insertInSectionController:self atIndexes:[NSIndexSet indexSetWithIndex:1]];
} completion:nil];

// OLD
[self.collectionContext reloadSectionController:self];

// NEW
[self.collectionContext performBatchAnimated:YES updates:^(id<IGListBatchContext> batchContext) {
  [batchContext reloadSectionController:self];
} completion:nil];
```

- `-[IGListCollectionContext containerSize]` no longer accounts for the content inset of the collection view when returning a size. If you require that behavior, you can now use `-[IGListCollectionContext insetContainerSize]`. [Ryan Nystrom](https://github.com/rnystrom) [(623ff2a)](https://github.com/Instagram/IGListKit/commit/623ff2a8a85e0e2e8d0331ae3250d67985cd06b6)

- `IGListCollectionView` has been **completely removed** in favor of using plain old `UICollectionView`. See discussion at [#409](https://github.com/Instagram/IGListKit/issues/409) for details. [Jesse Squires](https://github.com/jessesquires) [(2284ce3)](https://github.com/Instagram/IGListKit/commit/2284ce389708f62d99f48ff2ec15644f1ec59537)

- `IGListBatchUpdateData` replaced its `NSSet` properties with `NSArray` instead. [Ryan Nystrom](https://github.com/rnystrom) [(#616)](https://github.com/Instagram/IGListKit/pull/616)

- `IGListUpdatingDelegate` now requires method `-reloadItemInCollectionView:fromIndexPath:toIndexPath:` to handle reloading cells between index paths. [Ryan Nystrom](https://github.com/rnystrom) [(#657)](https://github.com/Instagram/IGListKit/pull/657)

- `-[IGListCollectionContext sectionForSectionController:]` has been removed and replaced with the `NSInteger sectionIndex` property on `IGListSectionController`. [Andrew Monshizadeh](https://github.com/amonshiz) [#671](http://github.com/Instagram/IGListKit/pull/671)

### Enhancements

- Added an initializer on `IGListAdapter` that does not take a `workingRangeSize` and defaults it to 0. [BasThomas](https://github.com/BasThomas) [(#686)](https://github.com/Instagram/IGListKit/pull/686)

- Added `-[IGListAdapter visibleCellsForObject:]` API. [Sherlouk](https://github.com/Sherlouk) [(#442)](https://github.com/Instagram/IGListKit/pull/442)

- Added `-[IGListAdapter sectionControllerForSection:]` API. [Adlai-Holler](https://github.com/Adlai-Holler) [(#477)](https://github.com/Instagram/IGListKit/pull/477)

- You can now manually move items (cells) within a section controller, ex: `[self.collectionContext moveInSectionController:self fromIndex:0 toIndex:1]`. [Ryan Nystrom](https://github.com/rnystrom) [(#418)](https://github.com/Instagram/IGListKit/pull/418)

- Invalidate the layout of a section controller and control the transition with `UIView` animation APIs. [Ryan Nystrom](https://github.com/rnystrom) [(#499)](https://github.com/Instagram/IGListKit/pull/499)

- Added `-[IGListAdapter visibleIndexPathsForSectionController:]` API. [Malecks](https://github.com/Malecks) [(#465)](https://github.com/Instagram/IGListKit/pull/465)

- Added `IGListBindingSectionController` which automatically binds view models to cells and animates updates at the cell level. [Ryan Nystrom](https://github.com/rnystrom) [(#494)](https://github.com/Instagram/IGListKit/pull/494)

- Added `IGListGenericSectionController` to take advantage of Objective-C (and Swift) generics and automatically store strongly-typed references to the object powering your section controller. [Ryan Nystrom](https://github.com/rnystrom) ([301f147](https://github.com/Instagram/IGListKit/commit/301f1471c9a7a802320e07890f5e98f15ada4e2e))

- Added a debug option for IGListKit that you can print to lldb via `po [IGListDebugger dump]`. [Ryan Nystrom](https://github.com/rnystrom) [(#617)](https://github.com/Instagram/IGListKit/pull/617)

### Fixes

- Gracefully handle a `nil` section controller returned by an `IGListAdapterDataSource`. [Ryan Nystrom](https://github.com/rnystrom) [(#488)](https://github.com/Instagram/IGListKit/pull/488)

- Fix bug where emptyView's hidden status is not updated after the number of items is changed with `insertInSectionController:atIndexes:` or related methods. [Peter Edmonston](https://github.com/edmonston) [(#395)](https://github.com/Instagram/IGListKit/pull/395)

- Fix bug where `IGListStackedSectionController`'s children need to know `numberOrItems` before didUpdate is called. [(#348)](https://github.com/Instagram/IGListKit/pull/390)

- Fix bug where `-[UICollectionViewCell ig_setStackedSectionControllerIndex:]` should use `OBJC_ASSOCIATION_COPY_NONATOMIC` for NSNumber. [PhilCai](https://github.com/PhilCai1993) [(#424)](https://github.com/Instagram/IGListKit/pull/426)

- Fix potential bug with suppressing animations (by passing `NO`) during `-[IGListAdapter performUpdatesAnimated: completion:]` where user would see UI glitches/flashing. [Jesse Squires](https://github.com/jessesquires) [(019c990)](https://github.com/Instagram/IGListKit/commit/019c990312eea4203c7388a83b50685d426aa372)

- Fix bug where scroll position would be incorrect in call to `-[IGListAdapter scrollToObject:supplementaryKinds:scrollDirection:scrollPosition:animated:` with scrollDirection/scrollPosition of UICollectionViewScrollDirectionVertical/UICollectionViewScrollPositionCenteredVertically or UICollectionViewScrollDirectionHorizontal/UICollectionViewScrollPositionCenteredHorizontally and with a collection view with nonzero contentInset. [David Yamnitsky](https://github.com/nitsky) [(5cc0fcd)](https://github.com/Instagram/IGListKit/commit/5cc0fcd1d77d6296f57ce1c298301b9881cb4d4a)

- Fix a crash when reusing collection views between embedded `IGListAdapter`s. [Ryan Nystrom](https://github.com/rnystrom) [(#517)](https://github.com/Instagram/IGListKit/pull/517)

- Only collect batch updates when explicitly inside the batch update block, execute them otherwise. Fixes dropped updates. [Ryan Nystrom](https://github.com/rnystrom) [(#494)](https://github.com/Instagram/IGListKit/pull/494)

- Remove objects that return `nil` diff identifiers before updating. [Ryan Nystrom](https://github.com/rnystrom) [(af984ca)](https://github.com/Instagram/IGListKit/commit/af984ca81d4d8c4ba3012be1a45f69670a832ccf)

- Fix a potential crash when a section is moved and deleted at the same time. [Ryan Nystrom](https://github.com/rnystrom) [(#577)](https://github.com/Instagram/IGListKit/pull/577)

- Prevent section controllers and supplementary sources from returning negative sizes that crash `UICollectionViewFlowLayout`. [Ryan Nystrom](https://github.com/rnystrom) [(#583)](https://github.com/Instagram/IGListKit/pull/583)

- Add nullability annotations to a few more headers. [Adlai Holler](https://github.com/Adlai-Holler) [(#626)](https://github.com/Instagram/IGListKit/pull/626)

- Fix a crash when inserting or deleting from the same index within the same batch-update application. [Ryan Nystrom](https://github.com/rnystrom) [(#616)](https://github.com/Instagram/IGListKit/pull/616)

- `IGListSectionType` protocol was removed and its methods were absorted into the `IGListSectionController` base class with default implementations. [Ryan Nystrom](https://github.com/rnystrom) ([3102852](https://github.com/Instagram/IGListKit/commit/3102852ce258274e8727f9094695a9c331e1abf3))

- When setting the collection view on `IGListAdapter`, its layout is now properly invalidated. [Jesse Squires](https://github.com/jessesquires) [(#677)](https://github.com/Instagram/IGListKit/pull/677)

- Fixes a bug when reusing `UICollectionView`s with multiple `IGListAdapter`s in an embedded environment that would accidentally `nil` the `collectionView` property of another adapter. [Ryan Nystrom](https://github.com/rnystrom) [(#721)](https://github.com/Instagram/IGListKit/pull/721)

- Fixes a bug where maintaining a reference to a section controller but not the list adapter in an async block could lead to calling `-[IGListAdapter sectionForSectionController:]` (or checking `-[IGListSectionController sectionIndex]`) and receiving an incorrect value. With the adapter check the value would be 0 because the adapter was `nil` and for the section controller property the value would be the last set index value. [Andrew Monshizadeh](https://github.com/amonshiz) [(#709)](https://github.com/Instagram/IGListKit/issues/709)

2.1.0
-----

This release closes the [2.1.0 milestone](https://github.com/Instagram/IGListKit/milestone/2).

### Enhancements

- Added support for macOS. Note: this is *only* for the Diffing components. There is **no support** for `IGListAdapter`, `IGListSectionController`, and other components at this time. [Guilherme Rambo](https://github.com/insidegui) [(#235)](https://github.com/Instagram/IGListKit/pull/235)

- Added a [macOS example](https://github.com/Instagram/IGListKit/tree/master/Examples/Examples-macOS) project. [Guilherme Rambo](https://github.com/insidegui) [(#337)](https://github.com/Instagram/IGListKit/pull/337)

- Disables `prefetchEnabled` by default on `IGListCollectionView`. [Sven Bacia](https://github.com/svenbacia) [(#323)](https://github.com/Instagram/IGListKit/pull/323)

- Working ranges now work with `IGListStackedSectionController`. [Ryan Nystrom](https://github.com/rnystrom) [(#356)](https://github.com/Instagram/IGListKit/pull/356)

- Added CocoaPods subspec for diffing, `IGListKit/Diffing` and an [installation guide](https://instagram.github.io/IGListKit/installation.html). [Sherlouk](https://github.com/Sherlouk) [(#368)](https://github.com/Instagram/IGListKit/pull/368)

- Added `allowsBackgroundReloading` flag (default `YES`) to `IGListAdapterUpdater` so users can configure this behavior as needed. [Adlai-Holler](https://github.com/Adlai-Holler) [(#375)](https://github.com/Instagram/IGListKit/pull/375)

- `-[IGListAdapter updater]` is now public (read-only). [Adlai-Holler](https://github.com/Adlai-Holler) [(#379)](https://github.com/Instagram/IGListKit/pull/379)

### Fixes

- Avoid `UICollectionView` crashes when queueing a reload and insert/delete on the same item as well as reloading an item in a section that is animating. [Ryan Nystrom](https://github.com/rnystrom) [(#325)](https://github.com/Instagram/IGListKit/pull/325)

- Prevent adapter data source from deallocating after queueing an update. [Ryan Nystrom](https://github.com/rnystrom) [(4cc91a2)](https://github.com/Instagram/IGListKit/commit/4cc91a25c8b262953e4f2d8e5dc78ee15c6265b2)

- Fix out-of-bounds bug when child section controllers in a stack remove cells. [Ryan Nystrom](https://github.com/rnystrom) [(#358)](https://github.com/Instagram/IGListKit/pull/358)

- Fix a grid layout bug when item has full-width and iter-item spacing is not zero. [Bofei Zhu](https://github.com/zhubofei) [(#361)](https://github.com/Instagram/IGListKit/pull/361)

2.0.0
-----

This release closes the [2.0.0 milestone](https://github.com/Instagram/IGListKit/milestone/1?closed=1). We've increased test coverage to 97%. Thanks to the [27 contributors](https://github.com/Instagram/IGListKit/graphs/contributors) who helped with this release!

You can find a [migration guide here](https://instagram.github.io/IGListKit/migration.html) to assist with migrating between 1.0 and 2.0.

### Breaking Changes

- Diff result method on `IGListIndexPathResult` changed. `-resultWithUpdatedMovesAsDeleteInserts` was removed and replaced with `-resultForBatchUpdates` [(b5aa5e3)](https://github.com/Instagram/IGListKit/commit/b5aa5e39002854c947e777c11ae241f67f24d19c)

```
// OLD
- (IGListIndexPathResult *)resultWithUpdatedMovesAsDeleteInserts;

// NEW
- (IGListIndexPathResult *)resultForBatchUpdates;
```

- `IGListDiffable` equality method changed from `isEqual:` to `isEqualToDiffableObject:` [(ab890fc)](https://github.com/Instagram/IGListKit/commit/ab890fc6070f170a2db5a383a6296e62dcf75678)

- The default `NSObject<IGListDiffable>` category was removed and replaced with `NSString<IGListDiffable>` and `NSNumber<IGListDiffable>` categories. All other models will need to conform to `IGListDiffable`. [(3947600)](https://github.com/Instagram/IGListKit/commit/394760081c7c2daa5ae6c18e00cdeaf2b67e22c1)

- Added support for specifying an end position when scrolling. [Bofei Zhu](https://github.com/zhubofei) [(#196)](https://github.com/Instagram/IGListKit/pull/196). The `IGListAdapter` scrolling method changed:

```objc
// OLD
- (void)scrollToObject:(id)object
    supplementaryKinds:(nullable NSArray<NSString *> *)supplementaryKinds
       scrollDirection:(UICollectionViewScrollDirection)scrollDirection
              animated:(BOOL)animated;

// NEW
- (void)scrollToObject:(id)object
    supplementaryKinds:(nullable NSArray<NSString *> *)supplementaryKinds
       scrollDirection:(UICollectionViewScrollDirection)scrollDirection
        scrollPosition:(UICollectionViewScrollPosition)scrollPosition
              animated:(BOOL)animated;
```

### Fixes

- Consider supplementary views with display and end-display events. [Ryan Nystrom](https://github.com/rnystrom) [(#470)](https://github.com/Instagram/IGListKit/pull/470)


- Changed `NSUInteger` to `NSInteger` in all public APIs. [Suraya Shivji](https://github.com/surayashivji) [(#200)](https://github.com/Instagram/IGListKit/issues/200)

### Enhancements

- Added support for supplementaryViews created from nibs. [Rawlinxx](https://github.com/rawlinxx) [(#90)](https://github.com/Instagram/IGListKit/pull/90)

- Added support for cells created from nibs. [Sven Bacia](https://github.com/svenbacia) [(#56)](https://github.com/Instagram/IGListKit/pull/56)

- Added an additional initializer for `IGListSingleSectionController` to be able to support single sections created from nibs. An example can be found [here](https://github.com/Instagram/IGListKit/tree/master/Examples/Examples-iOS/IGListKitExamples/ViewControllers/SingleSectionViewController.swift). [(#56)](https://github.com/Instagram/IGListKit/pull/56)

```objc
- (instancetype)initWithNibName:(NSString *)nibName
                         bundle:(nullable NSBundle *)bundle
                 configureBlock:(IGListSingleSectionCellConfigureBlock)configureBlock
                      sizeBlock:(IGListSingleSectionCellSizeBlock)sizeBlock;
```

- Added `-isFirstSection` and `-isLastSection` APIs to `IGListSectionController` [(316fbe2)](https://github.com/Instagram/IGListKit/commit/316fbe2b8b2508b58a0f38387c3a343b9c37e282)

- Added support for cells and supplementaryViews created from storyboard. There's a new required method on the `IGListCollectionContext` protocol to do this. [Bofei Zhu](https://github.com/zhubofei) [(#92)](https://github.com/Instagram/IGListKit/pull/92)

```objc
// IGListCollectionContext
- (__kindof UICollectionViewCell *)dequeueReusableCellFromStoryboardWithIdentifier:(NSString *)identifier
                                                              forSectionController:(IGListSectionController<IGListSectionType> *)sectionController
                                                                           atIndex:(NSInteger)index;
```

- Added `tvOS` support. [Jesse Squires](https://github.com/jessesquires) [(#137)](https://github.com/Instagram/IGListKit/pull/137)

- Added `-[IGListAdapter visibleObjects]` API. [Ryan Nystrom](https://github.com/rnystrom) [(386ae07)](https://github.com/Instagram/IGListKit/commit/386ae0786445c06e1eabf074a4181614332f155f)

- Added `-[IGListAdapter objectForSectionController:]` API. [Ayush Saraswat](https://github.com/saraswatayu) [(#204)](https://github.com/Instagram/IGListKit/pull/204)

- Added `IGListGridCollectionViewLayout`, a section-based grid layout. [Bofei Zhu](https://github.com/zhubofei) [(#225)](https://github.com/Instagram/IGListKit/pull/225)

- Added support for scrolling to an index in a section controller from within that section controller. There's a new required method on the `IGListCollectionContext` protocol to do this. [Jesse Squires](https://github.com/jessesquires) [(e5afb5b)](https://github.com/Instagram/IGListKit/commit/e5afb5b4d0cfc70a2736b02279b6bc239ddf1e5d)

```objc
// IGListCollectionContext
- (void)scrollToSectionController:(IGListSectionController<IGListSectionType> *)sectionController
                          atIndex:(NSInteger)index
                   scrollPosition:(UICollectionViewScrollPosition)scrollPosition
                         animated:(BOOL)animated;
```

### Fixes

- Fixed `-[IGListAdapter reloadDataWithCompletion:]` not returning early when `collectionView` or `dataSource` is `nil` and `completion` is `nil`. [Ben Asher](https://github.com/benasher44) [(#51)](https://github.com/Instagram/IGListKit/pull/51)

- Prevent `UICollectionView` bug when accessing a cell during working range updates. [Ryan Nystrom](https://github.com/rnystrom) [(#216)](https://github.com/Instagram/IGListKit/pull/216)

- Skip reloading for objects that are not found when calling `-[IGListAdapter reloadObjects:]`. [Ryan Nystrom](https://github.com/rnystrom) [(ca15e29)](https://github.com/Instagram/IGListKit/commit/ca15e29cf1dadc6c396fe8f14f16c27f6a38519c)

- Fixes a crash when a reload is queued for an object that is deleted in the same runloop turn. [Ryan Nystrom](https://github.com/rnystrom) [(7c3d499)](https://github.com/Instagram/IGListKit/commit/7c3d4999ebde36ee4666e5aee99716d1ed1fb2d8)

- Fixed a bug where `IGListStackSectionController` would only set its supplementary source once. [Ryan Nystrom](https://github.com/rnystrom) [(#286)](https://github.com/Instagram/IGListKit/pull/286)

- Fixed a bug where `IGListStackSectionController` passed the wrong section controller for will-drag scroll events. [Ryan Nystrom](https://github.com/rnystrom) [(#286)](https://github.com/Instagram/IGListKit/pull/286)

- Fixed a crash when deselecting a cell through a child section controller in an `IGListStackSectionController`. [Ryan Nystrom](https://github.com/rnystrom) [(#295)](https://github.com/Instagram/IGListKit/pull/295)

### Documentation

- We now have 100% documentation coverage. Docs been refined and clarified. [Jesse Squires](https://github.com/jessesquires) [(#207)](https://github.com/Instagram/IGListKit/pull/207)

- Added new Guides: [Getting Started](https://instagram.github.io/IGListKit/getting-started.html), [Migration](https://instagram.github.io/IGListKit/migration.html)

- Added examples for Today & iMessage extensions. [Sherlouk](https://github.com/Sherlouk) [(#112)](https://github.com/Instagram/IGListKit/pull/112)

- Added `tvOS` example pack. [Sherlouk](https://github.com/Sherlouk) [(#141)](https://github.com/Instagram/IGListKit/pull/141)

1.0.0
-----

Initial release. :tada:
