Select an item through IGListCollectionContext

CHANGELOG.md

@@ -12,6 +12,7 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 ### Enhancements
 
 - Added `-[IGListSectionController didDeselectItemAtIndex:]` API to support default `UICollectionView` cell deselection. [Ryan Nystrom](https://github.com/rnystrom) (tbd)
+- Added `-[IGListCollectionContext selectItemAtIndex:]` Select an item through IGListCollectionContext like `-[IGListCollectionContext deselectItemAtIndex:]`. [Marvin Nazari](https://github.com/MarvinNazari) (tbd)
 
 3.0.0
 -----

Source/IGListAdapter.m

@@ -806,6 +806,16 @@ - (void)deselectItemAtIndex:(NSInteger)index
     [self.collectionView deselectItemAtIndexPath:indexPath animated:animated];
 }
 
+- (void)selectItemAtIndex:(NSInteger)index
+        sectionController:(IGListSectionController *)sectionController
+                 animated:(BOOL)animated
+            scrollPosition:(UICollectionViewScrollPosition)scrollPosition {
+    IGAssertMainThread();
+    IGParameterAssert(sectionController != nil);
+    NSIndexPath *indexPath = [self indexPathForSectionController:sectionController index:index usePreviousIfInUpdateBlock:NO];
+    [self.collectionView selectItemAtIndexPath:indexPath animated:animated scrollPosition:scrollPosition];
+}
+
 - (__kindof UICollectionViewCell *)dequeueReusableCellOfClass:(Class)cellClass
                                          forSectionController:(IGListSectionController *)sectionController
                                                       atIndex:(NSInteger)index {

Source/IGListCollectionContext.h

@@ -99,6 +99,19 @@ NS_SWIFT_NAME(ListCollectionContext)
           sectionController:(IGListSectionController *)sectionController
                    animated:(BOOL)animated;
 
+/**
+ Selects a cell in the collection.
+
+ @param index The index of the item to select.
+ @param sectionController The section controller requesting this information.
+ @param animated Pass `YES` to animate the change, `NO` otherwise.
+ @param scrollPosition An option that specifies where the item should be positioned when scrolling finishes.
+ */
+- (void)selectItemAtIndex:(NSInteger)index
+        sectionController:(IGListSectionController *)sectionController
+                 animated:(BOOL)animated
+           scrollPosition:(UICollectionViewScrollPosition)scrollPosition;
+
 /**
  Dequeues a cell from the collection view reuse pool.
 

Source/IGListStackedSectionController.m

@@ -225,6 +225,14 @@ - (void)deselectItemAtIndex:(NSInteger)index sectionController:(IGListSectionCon
     [self.collectionContext deselectItemAtIndex:offsetIndex sectionController:self animated:animated];
 }
 
+- (void)selectItemAtIndex:(NSInteger)index
+        sectionController:(IGListSectionController *)sectionController
+                 animated:(BOOL)animated
+           scrollPosition:(UICollectionViewScrollPosition)scrollPosition {
+    const NSInteger offsetIndex = [self relativeIndexForSectionController:sectionController fromLocalIndex:index];
+    [self.collectionContext selectItemAtIndex:offsetIndex sectionController:self animated:animated scrollPosition:scrollPosition];
+}
+
 - (UICollectionViewCell *)dequeueReusableCellOfClass:(Class)cellClass
                                 forSectionController:(IGListSectionController *)sectionController
                                              atIndex:(NSInteger)index {

Tests/IGListAdapterTests.m

@@ -969,6 +969,15 @@ - (void)test_whenDeselectingThroughContext_thatCellDeselected {
     XCTAssertFalse([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
 }
 
+- (void)test_whenSelectingThroughContext_thatCellSelected {
+    self.dataSource.objects = @[@1, @2, @3];
+    [self.adapter reloadDataWithCompletion:nil];
+
+    NSIndexPath *path = [NSIndexPath indexPathForItem:0 inSection:0];
+    [self.adapter selectItemAtIndex:0 sectionController:[self.adapter sectionControllerForObject:@1] animated:NO scrollPosition:UICollectionViewScrollPositionTop];
+    XCTAssertTrue([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
+}
+
 - (void)test_whenScrollingToIndex_withSectionController_thatPositionCorrect {
     self.dataSource.objects = @[@1, @2, @3, @4, @5, @6, @7, @8, @9, @10, @11, @12, @13, @14, @15, @16, @17, @18, @19];
     [self.adapter reloadDataWithCompletion:nil];

Tests/IGListStackSectionControllerTests.m

@@ -826,6 +826,20 @@ - (void)test_whenDeselectingChildSectionControllerIndex_thatCorrectCellDeselecte
     XCTAssertFalse([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
 }
 
+- (void)test_whenSelectingChildSectionControllerIndex_thatCorrectCellSelected {
+    [self setupWithObjects:@[
+                             [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@1 value:@[@1, @1]]
+                             ]];
+
+    NSIndexPath *path = [NSIndexPath indexPathForItem:1 inSection:1];
+
+    IGListStackedSectionController *stack = [self.adapter sectionControllerForObject:self.dataSource.objects.lastObject];
+    IGListSectionController *section = stack.sectionControllers.lastObject;
+    [section.collectionContext selectItemAtIndex:0 sectionController:section animated:NO scrollPosition:UICollectionViewScrollPositionTop];
+    XCTAssertTrue([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
+}
+
 - (void)test_whenRemovingSection_withWorkingRange_thatChildSectionControllersReceiveEvents {
     [self setupWithObjects:@[
                              [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2, @3]],