Working ranges in stacked section controllers

Summary: Closes #354 - [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 #356 Differential Revision: D4365718 Pulled By: jessesquires fbshipit-source-id: 41d7bcd823415e5795a069a4ef335e60e7da806a
Instagram · Dec 23, 2016 · e9ad6b1 · e9ad6b1
1 parent c3c0e36
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -15,6 +15,8 @@ This release closes the [2.1.0 milestone](https://github.com/Instagram/IGListKit
 
 - 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)
+
 ### 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)

diff --git a/Source/IGListStackedSectionController.m b/Source/IGListStackedSectionController.m
@@ -56,6 +56,7 @@ - (instancetype)initWithSectionControllers:(NSArray <IGListSectionController<IGL
 
         self.displayDelegate = self;
         self.scrollDelegate = self;
+        self.workingRangeDelegate = self;
 
         [self reloadData];
     }
@@ -363,4 +364,18 @@ - (void)listAdapter:(IGListAdapter *)listAdapter didEndDraggingSectionController
     }
 }
 
+#pragma mark - IGListWorkingRangeDelegate
+
+- (void)listAdapter:(IGListAdapter *)listAdapter sectionControllerWillEnterWorkingRange:(IGListSectionController<IGListSectionType> *)sectionController {
+    for (IGListSectionController<IGListSectionType> *childSectionController in self.sectionControllers) {
+        [[childSectionController workingRangeDelegate] listAdapter:listAdapter sectionControllerWillEnterWorkingRange:childSectionController];
+    }
+}
+
+- (void)listAdapter:(IGListAdapter *)listAdapter sectionControllerDidExitWorkingRange:(IGListSectionController<IGListSectionType> *)sectionController {
+    for (IGListSectionController<IGListSectionType> *childSectionController in self.sectionControllers) {
+        [[childSectionController workingRangeDelegate] listAdapter:listAdapter sectionControllerDidExitWorkingRange:childSectionController];
+    }
+}
+
 @end
diff --git a/Source/Internal/IGListStackedSectionControllerInternal.h b/Source/Internal/IGListStackedSectionControllerInternal.h
@@ -15,7 +15,8 @@
 <
 IGListCollectionContext,
 IGListDisplayDelegate,
-IGListScrollDelegate
+IGListScrollDelegate,
+IGListWorkingRangeDelegate
 >
 
 @property (nonatomic, strong, readonly) NSOrderedSet<__kindof IGListSectionController<IGListSectionType> *> *sectionControllers;

diff --git a/Tests/IGListStackSectionControllerTests.m b/Tests/IGListStackSectionControllerTests.m
@@ -54,7 +54,7 @@ - (void)setUp {
     self.collectionView.frame = kStackTestFrame;
 
     self.dataSource = [[IGTestStackedDataSource alloc] init];
-    self.adapter = [[IGListAdapter alloc] initWithUpdater:[IGListAdapterUpdater new] viewController:nil workingRangeSize:0];
+    self.adapter = [[IGListAdapter alloc] initWithUpdater:[IGListAdapterUpdater new] viewController:nil workingRangeSize:1];
 }
 
 - (void)tearDown {
@@ -702,6 +702,57 @@ - (void)test_whenDeselectingChildSectionControllerIndex_thatCorrectCellDeselecte
     XCTAssertFalse([[self.collectionView cellForItemAtIndexPath:path] isSelected]);
 }
 
+- (void)test_whenRemovingSection_withWorkingRange_thatChildSectionControllersReceiveEvents {
+    [self setupWithObjects:@[
+                             [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@1 value:@[@1, @1]]
+                             ]];
+
+    IGListStackedSectionController *stack = [self.adapter sectionControllerForObject:self.dataSource.objects.firstObject];
+    IGListTestSection *section = stack.sectionControllers.firstObject;
+
+    id mockDelegate = [OCMockObject mockForProtocol:@protocol(IGListWorkingRangeDelegate)];
+    [[mockDelegate expect] listAdapter:self.adapter sectionControllerDidExitWorkingRange:section];
+
+    section.workingRangeDelegate = mockDelegate;
+
+    self.dataSource.objects = @[
+                                [[IGTestObject alloc] initWithKey:@1 value:@[@1, @1]],
+                                ];
+
+    XCTestExpectation *expectation = [self expectationWithDescription:NSStringFromSelector(_cmd)];
+
+    [self.adapter performUpdatesAnimated:YES completion:^(BOOL finished) {
+        [mockDelegate verify];
+        [expectation fulfill];
+    }];
+
+    [self waitForExpectationsWithTimeout:15 handler:nil];
+}
+
+- (void)test_whenScrolling_withWorkingRange_thatChildSectionControllersReceiveEvents {
+    [self setupWithObjects:@[
+                             [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@1 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@2 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@3 value:@[@1, @2, @3]],
+                             [[IGTestObject alloc] initWithKey:@4 value:@[@1, @1]]
+                             ]];
+
+    IGListStackedSectionController *stack = [self.adapter sectionControllerForObject:self.dataSource.objects.lastObject];
+    IGListTestSection *section = stack.sectionControllers.firstObject;
+
+    id mockDelegate = [OCMockObject mockForProtocol:@protocol(IGListWorkingRangeDelegate)];
+    [[mockDelegate expect] listAdapter:self.adapter sectionControllerWillEnterWorkingRange:section];
+
+    section.workingRangeDelegate = mockDelegate;
+
+    [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:0 inSection:4] atScrollPosition:UICollectionViewScrollPositionTop animated:NO];
+    [self.collectionView layoutIfNeeded];
+
+    [mockDelegate verify];
+}
+
 - (void)test_whenRemovingCellsFromChild_thatStackSendsDisplayEventsCorrectly {
     IGTestObject *object = [[IGTestObject alloc] initWithKey:@0 value:@[@1, @2]];
     [self setupWithObjects:@[object]];