The markdown parsing is broken/disabled for release notes. Sorry about that, I'm chasing the source of a crash that's been bringing this website down for the last couple of days.
# 4.0.0
4.0.0 is here! 🎉🎊🥳
This version has a number of improvements we've been working on for the last year. We're excited for everyone get their hands on the new improvements and features. Thanks so much to all who contributed code, submitted issues, and contributed to discussions around this release!
### 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/xohozu) [(#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/xohozu) [(#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)
### 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)
This release closes the [3.1.0 milestone](https://github.com/Instagram/IGListKit/milestone/4).
### 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)
### 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)
### Enhancements
- 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)
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)
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)
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;
```
- 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)
### Our First production release 🎉
Take a look at the [documentation](https://instagram.github.io/IGListKit/), add `IGListKit` to your [Podfile](https://cocoapods.org/pods/IGListKit), or take a pass at some of our [starter tasks](https://github.com/Instagram/IGListKit/issues?q=is%3Aissue+is%3Aopen+label%3Astarter-task).
We're launching at version 1.0 because of how widely used the framework is here at Instagram, but looking forward to enhancing and extending the framework even further. 🚀