Backed out changeset b72b444c1197

Summary: This diff isn't correct, and the Instagram cut happens today. Pulling back so I have time to test the correct change more throughly.

Reviewed By: rnystrom

Differential Revision: D4550149

fbshipit-source-id: 2e882caeb9ef999b7fd57562740b352ea8edfa5f

CHANGELOG.md

@@ -24,11 +24,6 @@ This release closes the [3.0.0 milestone](https://github.com/Instagram/IGListKit
 
 - 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)
 
-### Enhancements
-
-- Empty Views now move with Refresh Controls, and no longer use the `_collectionView.backgroundView` property. [dshahidehpour](https://github.com/dshahidehpour) [(#462)](https://github.com/Instagram/IGListKit/pull/462)]
-
-
 ### Enhancements
 
 - 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)

Source/IGListAdapter.m

@@ -540,22 +540,15 @@
     if (self.isInUpdateBlock) {
         return; // will be called again when update block completes
     }
-
-    if (shouldHide) {
-        _emptyListView.hidden = YES;
-    } else {
-        UIView *newBackgroundView = [self.dataSource emptyViewForListAdapter:self];
-        if (_emptyListView != newBackgroundView) {
-            [_emptyListView removeFromSuperview];
-            _emptyListView = newBackgroundView;
-        }
-
-        if (_emptyListView != nil) {
-            _emptyListView.frame = _collectionView.bounds;
-            _emptyListView.hidden = NO;
-            [_collectionView addSubview:(id)_emptyListView];
-        }
+    UIView *backgroundView = [self.dataSource emptyViewForListAdapter:self];
+    // don't do anything if the client is using the same view
+    if (backgroundView != _collectionView.backgroundView) {
+        // collection view will just stack the background views underneath each other if we do not remove the previous
+        // one first. also fine if it is nil
+        [_collectionView.backgroundView removeFromSuperview];
+        _collectionView.backgroundView = backgroundView;
     }
+    _collectionView.backgroundView.hidden = shouldHide;
 }
 
 - (BOOL)itemCountIsZero {

Source/IGListAdapterDataSource.h

@@ -56,8 +56,9 @@ NS_ASSUME_NONNULL_BEGIN
 
  @return A view to use as the collection view background, or `nil` if you don't want a background view.
 
- @note This method is lazily evaluated, meaning, we won't ask for the empty view until it is necessary to display it.
- You are free to return new views every time, but for performance reasons you may want to retain the view and return it here.
+ @note This method is called every time the list adapter is updated. You are free to return new views every time,
+ but for performance reasons you may want to retain the view and return it here. The infra is only responsible for
+ adding the background view and maintaining its visibility.
  */
 - (nullable UIView *)emptyViewForListAdapter:(IGListAdapter *)listAdapter;
 

Source/Internal/IGListAdapterInternal.h

@@ -40,7 +40,7 @@ IGListCollectionContext
 
 @property (nonatomic, strong, nullable) IGListAdapterProxy *delegateProxy;
 
-@property (nonatomic, strong, nullable) UIView *emptyListView;
+@property (nonatomic, strong, nullable) UIView *emptyBackgroundView;
 
 /**
  When making object updates inside a batch update block, delete operations must use the section /before/ any moves take

Tests/IGListAdapterTests.m

@@ -181,40 +181,19 @@ XCTAssertEqual(CGPointEqualToPoint(point, p), YES); \
     XCTAssertEqualObjects(identifier, @"IGNibNameUICollectionViewCell");
 }
 
-- (void)test_EmptyViewIsCreatedLazily {
-    UIView *emptyView = [[UIView alloc] init];
-    self.dataSource.emptyView = emptyView;
+- (void)test_whenDataSourceChanges_thatBackgroundViewVisibilityChanges {
     self.dataSource.objects = @[@1];
+    UIView *background = [[UIView alloc] init];
+    self.dataSource.backgroundView = background;
     __block BOOL executed = NO;
     [self.adapter reloadDataWithCompletion:^(BOOL finished) {
-        XCTAssertNil(self.adapter.emptyListView, @"Empty list view not correctly assigned");
+        XCTAssertTrue(self.adapter.collectionView.backgroundView.hidden, @"Background view should be hidden");
+        XCTAssertEqualObjects(background, self.adapter.collectionView.backgroundView, @"Background view not correctly assigned");
 
         self.dataSource.objects = @[];
         [self.adapter reloadDataWithCompletion:^(BOOL finished2) {
-            XCTAssertFalse(self.adapter.emptyListView.hidden, @"Empty list view should be visible");
-            XCTAssertEqualObjects(emptyView, self.adapter.emptyListView, @"Empty list view not correctly assigned");
-            executed = YES;
-        }];
-    }];
-    XCTAssertTrue(executed);
-}
-
-- (void)test_whenDataSourceChanges_thatEmptyViewVisibilityChanges {
-    UIView *emptyView = [[UIView alloc] init];
-    self.dataSource.emptyView = emptyView;
-    self.dataSource.objects = @[];
-    [self.adapter reloadDataWithCompletion:nil];
-
-    self.dataSource.objects = @[@1];
-    __block BOOL executed = NO;
-    [self.adapter reloadDataWithCompletion:^(BOOL finished) {
-        XCTAssertTrue(self.adapter.emptyListView.hidden, @"Empty list view should be hidden");
-        XCTAssertEqualObjects(emptyView, self.adapter.emptyListView, @"Empty list view not correctly assigned");
-
-        self.dataSource.objects = @[];
-        [self.adapter reloadDataWithCompletion:^(BOOL finished2) {
-            XCTAssertFalse(self.adapter.emptyListView.hidden, @"Empty list view should be visible");
-            XCTAssertEqualObjects(emptyView, self.adapter.emptyListView, @"Empty list view not correctly assigned");
+            XCTAssertFalse(self.adapter.collectionView.backgroundView.hidden, @"Background view should be visible");
+            XCTAssertEqualObjects(background, self.adapter.collectionView.backgroundView, @"Background view not correctly assigned");
             executed = YES;
         }];
     }];
@@ -336,54 +315,54 @@ XCTAssertEqual(CGPointEqualToPoint(point, p), YES); \
 
 - (void)test_whenDataSourceAddsItems_thatEmptyViewBecomesVisible {
     self.dataSource.objects = @[];
-    UIView *emptyView = [UIView new];
-    self.dataSource.emptyView = emptyView;
+    UIView *background = [UIView new];
+    self.dataSource.backgroundView = background;
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertEqual(self.adapter.emptyListView, emptyView);
-    XCTAssertFalse(self.adapter.emptyListView.hidden);
+    XCTAssertEqual(self.collectionView.backgroundView, background);
+    XCTAssertFalse(self.collectionView.backgroundView.hidden);
     self.dataSource.objects = @[@2];
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertTrue(self.adapter.emptyListView.hidden);
+    XCTAssertTrue(self.collectionView.backgroundView.hidden);
 }
 
 - (void)test_whenInsertingIntoEmptySection_thatEmptyViewBecomesHidden {
     self.dataSource.objects = @[@0];
-    self.dataSource.emptyView = [UIView new];
+    self.dataSource.backgroundView = [UIView new];
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertFalse(self.adapter.emptyListView.hidden);
+    XCTAssertFalse(self.collectionView.backgroundView.hidden);
     IGListTestSection *sectionController = [self.adapter sectionControllerForObject:@(0)];
     sectionController.items = 1;
     [self.adapter insertInSectionController:sectionController atIndexes:[NSIndexSet indexSetWithIndex:0]];
-    XCTAssertTrue(self.adapter.emptyListView.hidden);
+    XCTAssertTrue(self.collectionView.backgroundView.hidden);
 }
 
 - (void)test_whenDeletingAllItemsFromSection_thatEmptyViewBecomesVisible {
     self.dataSource.objects = @[@1];
-    self.dataSource.emptyView = [UIView new];
+    self.dataSource.backgroundView = [UIView new];
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertNil(self.adapter.emptyListView);
+    XCTAssertTrue(self.collectionView.backgroundView.hidden);
     IGListTestSection *sectionController = [self.adapter sectionControllerForObject:@(1)];
     sectionController.items = 0;
     [self.adapter deleteInSectionController:sectionController atIndexes:[NSIndexSet indexSetWithIndex:0]];
-    XCTAssertFalse(self.adapter.emptyListView.hidden);
+    XCTAssertFalse(self.collectionView.backgroundView.hidden);
 }
 
 - (void)test_whenEmptySectionAddsItems_thatEmptyViewBecomesHidden {
     self.dataSource.objects = @[@0];
-    self.dataSource.emptyView = [UIView new];
+    self.dataSource.backgroundView = [UIView new];
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertFalse(self.adapter.emptyListView.hidden);
+    XCTAssertFalse(self.collectionView.backgroundView.hidden);
     IGListTestSection *sectionController = [self.adapter sectionControllerForObject:@(0)];
     sectionController.items = 2;
     [self.adapter reloadSectionController:sectionController];
-    XCTAssertTrue(self.adapter.emptyListView.hidden);
+    XCTAssertTrue(self.collectionView.backgroundView.hidden);
 }
 
 - (void)test_whenSectionItemsAreDeletedAsBatch_thatEmptyViewBecomesVisible {
     self.dataSource.objects = @[@1, @2];
-    self.dataSource.emptyView = [UIView new];
+    self.dataSource.backgroundView = [UIView new];
     [self.adapter reloadDataWithCompletion:nil];
-    XCTAssertNil(self.adapter.emptyListView);
+    XCTAssertTrue(self.collectionView.backgroundView.hidden);
     IGListTestSection *firstSectionController = [self.adapter sectionControllerForObject:@(1)];
     IGListTestSection *secondSectionController = [self.adapter sectionControllerForObject:@(2)];
     XCTestExpectation *expectation =  [self expectationWithDescription:NSStringFromSelector(_cmd)];
@@ -394,7 +373,7 @@ XCTAssertEqual(CGPointEqualToPoint(point, p), YES); \
         NSIndexSet *indexesToDelete = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, 2)];
         [self.adapter deleteInSectionController:secondSectionController atIndexes:indexesToDelete];
     } completion:^(BOOL finished) {
-        XCTAssertFalse(self.adapter.emptyListView.hidden);
+        XCTAssertFalse(self.collectionView.backgroundView.hidden);
         [expectation fulfill];
     }];
     [self waitForExpectationsWithTimeout:15 handler:nil];

Tests/Objects/IGListTestAdapterDataSource.h

@@ -16,6 +16,6 @@
 // array of numbers which is then passed to -[IGListTestSection setItems:]
 @property (nonatomic, strong) NSArray <NSNumber *> *objects;
 
-@property (nonatomic, strong) UIView *emptyView;
+@property (nonatomic, strong) UIView *backgroundView;
 
 @end

Tests/Objects/IGListTestAdapterDataSource.m

@@ -25,7 +25,7 @@
 }
 
 - (nullable UIView *)emptyViewForListAdapter:(IGListAdapter *)listAdapter {
-    return self.emptyView;
+    return self.backgroundView;
 }
 
 @end