From e66bd85e32662f9375cf0c2c54132e46fde1af6b Mon Sep 17 00:00:00 2001
From: Ryan Nystrom <rnystrom@instagram.com>
Date: Tue, 6 Dec 2016 18:47:59 -0800
Subject: [PATCH] Fix deselection from stack collection context offset

Summary:
Offset should be relative.

Fixes #279

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/295

Differential Revision: D4290143

Pulled By: rnystrom

fbshipit-source-id: 8d6dccb821b12700d0d7e8704006ef5371396dfd
---
 CHANGELOG.md                              |  2 ++
 Source/IGListStackedSectionController.m   |  4 ++--
 Tests/IGListStackSectionControllerTests.m | 16 ++++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0aeee8a..23ec38c1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -113,6 +113,8 @@ You can find a [migration guide here](https://instagram.github.io/IGListKit/migr
 
 - 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)
+
 1.0.0
 -----
 
diff --git a/Source/IGListStackedSectionController.m b/Source/IGListStackedSectionController.m
index 366a3f25..16665ace 100644
--- a/Source/IGListStackedSectionController.m
+++ b/Source/IGListStackedSectionController.m
@@ -162,8 +162,8 @@
 }
 
 - (void)deselectItemAtIndex:(NSInteger)index sectionController:(IGListSectionController<IGListSectionType> *)sectionController animated:(BOOL)animated {
-    const NSUInteger localIndex = [self localIndexForSectionController:sectionController index:index];
-    [self.collectionContext deselectItemAtIndex:localIndex sectionController:self animated:animated];
+    const NSUInteger offsetIndex = [self relativeIndexForSectionController:sectionController fromLocalIndex:index];
+    [self.collectionContext deselectItemAtIndex:offsetIndex sectionController:self animated:animated];
 }
 
 - (NSInteger)sectionForSectionController:(IGListSectionController<IGListSectionType> *)sectionController {
diff --git a/Tests/IGListStackSectionControllerTests.m b/Tests/IGListStackSectionControllerTests.m
index fcfead45..63350f41 100644
--- a/Tests/IGListStackSectionControllerTests.m
+++ b/Tests/IGListStackSectionControllerTests.m
@@ -686,4 +686,20 @@ static const CGRect kStackTestFrame = (CGRect){{0.0, 0.0}, {100.0, 100.0}};
     XCTAssertEqual(self.collectionView.contentOffset.y, 170);
 }
 
+- (void)test_whenDeselectingChildSectionControllerIndex_thatCorrectCellDeselected {
+    [self setupWithObjects:@[
+                             [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@1 value:@[@1, @1]]
+                             ]];
+
+    NSIndexPath *path = [NSIndexPath indexPathForItem:1 inSection:1];
+    [self.collectionView selectItemAtIndexPath:path animated:NO scrollPosition:UICollectionViewScrollPositionTop];
+    XCTAssertTrue([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
+
+    IGListStackedSectionController *stack = [self.adapter sectionControllerForObject:self.dataSource.objects.lastObject];
+    IGListSectionController<IGListSectionType> *section = stack.sectionControllers.lastObject;
+    [section.collectionContext deselectItemAtIndex:0 sectionController:section animated:NO];
+    XCTAssertFalse([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
+}
+
 @end