IGListCollectionContext
@protocol IGListCollectionContext <NSObject>
The collection context provides limited access to the collection-related information that section controllers need for operations like sizing, dequeing cells, insterting, deleting, reloading, etc.
-
The size of the collection view. You can use this for sizing cells.
Declaration
Objective-C
@property (readonly, nonatomic) CGSize containerSize;
-
The content insets of the collection view. You can use this for sizing cells.
Declaration
Objective-C
@property (readonly, nonatomic) UIEdgeInsets containerInset;
-
The size of the collection view with content insets applied.
Declaration
Objective-C
@property (readonly, nonatomic) CGSize insetContainerSize;
-
Returns size of the collection view relative to the section controller.
Declaration
Objective-C
- (CGSize)containerSizeForSectionController: (nonnull IGListSectionController *)sectionController;
Parameters
sectionController
The section controller requesting this information.
Return Value
The size of the collection view minus the given section controller’s insets.
-
Returns the index of the specified cell in the collection relative to the section controller.
Declaration
Objective-C
- (NSInteger)indexForCell:(nonnull UICollectionViewCell *)cell sectionController:(nonnull IGListSectionController *)sectionController;
Parameters
cell
An existing cell in the collection.
sectionController
The section controller requesting this information.
Return Value
The index of the cell or
NSNotFound
if it does not exist in the collection. -
Returns the cell in the collection at the specified index for the section controller.
Warning
This method may return
nil
if the cell is offscreen.Declaration
Objective-C
- (nullable __kindof UICollectionViewCell *) cellForItemAtIndex:(NSInteger)index sectionController:(nonnull IGListSectionController *)sectionController;
Parameters
index
The index of the desired cell.
sectionController
The section controller requesting this information.
Return Value
The collection view cell, or
nil
if not found. -
Returns the visible cells for the given section controller.
Declaration
Objective-C
- (nonnull NSArray<UICollectionViewCell *> *)visibleCellsForSectionController: (nonnull IGListSectionController *)sectionController;
Parameters
sectionController
The section controller requesting this information.
Return Value
An array of visible cells, or an empty array if none are found.
-
Returns the visible paths for the given section controller.
Declaration
Objective-C
- (nonnull NSArray<NSIndexPath *> *)visibleIndexPathsForSectionController: (nonnull IGListSectionController *)sectionController;
Parameters
sectionController
The section controller requesting this information.
Return Value
An array of visible index paths, or an empty array if none are found.
-
Deselects a cell in the collection.
Declaration
Objective-C
- (void)deselectItemAtIndex:(NSInteger)index sectionController:(nonnull IGListSectionController *)sectionController animated:(BOOL)animated;
Parameters
index
The index of the item to deselect.
sectionController
The section controller requesting this information.
animated
Pass
YES
to animate the change,NO
otherwise. -
Dequeues a cell from the collection view reuse pool.
Note
This method uses a string representation of the cell class as the identifier.
Declaration
Objective-C
- (nonnull __kindof UICollectionViewCell *) dequeueReusableCellOfClass:(nonnull Class)cellClass forSectionController:(nonnull IGListSectionController *)sectionController atIndex:(NSInteger)index;
Parameters
cellClass
The class of the cell you want to dequeue.
sectionController
The section controller requesting this information.
index
The index of the cell.
Return Value
A cell dequeued from the reuse pool or a newly created one.
-
Dequeues a cell from the collection view reuse pool.
Note
This method uses a string representation of the cell class as the identifier.
Declaration
Objective-C
- (nonnull __kindof UICollectionViewCell *) dequeueReusableCellWithNibName:(nonnull NSString *)nibName bundle:(nullable NSBundle *)bundle forSectionController: (nonnull IGListSectionController *)sectionController atIndex:(NSInteger)index;
Parameters
nibName
The name of the nib file.
bundle
The bundle in which to search for the nib file. If
nil
, this method searches the main bundle.sectionController
The section controller requesting this information.
index
The index of the cell.
Return Value
A cell dequeued from the reuse pool or a newly created one.
-
Dequeues a storyboard prototype cell from the collection view reuse pool.
Declaration
Objective-C
- (nonnull __kindof UICollectionViewCell *) dequeueReusableCellFromStoryboardWithIdentifier:(nonnull NSString *)identifier forSectionController: (nonnull IGListSectionController *) sectionController atIndex:(NSInteger)index;
Parameters
identifier
The identifier of the cell prototype in storyboard.
sectionController
The section controller requesting this information.
index
The index of the cell.
Return Value
A cell dequeued from the reuse pool or a newly created one.
-
Dequeues a supplementary view from the collection view reuse pool.
Note
This method uses a string representation of the view class as the identifier.
Declaration
Objective-C
- (nonnull __kindof UICollectionReusableView *) dequeueReusableSupplementaryViewOfKind:(nonnull NSString *)elementKind forSectionController: (nonnull IGListSectionController *)sectionController class:(nonnull Class)viewClass atIndex:(NSInteger)index;
Parameters
elementKind
The kind of supplementary view.
sectionController
The section controller requesting this information.
viewClass
The class of the supplementary view.
index
The index of the supplementary view.
Return Value
A supplementary view dequeued from the reuse pool or a newly created one.
-
Dequeues a supplementary view from the collection view reuse pool.
Declaration
Objective-C
- (nonnull __kindof UICollectionReusableView *) dequeueReusableSupplementaryViewFromStoryboardOfKind: (nonnull NSString *)elementKind withIdentifier: (nonnull NSString *)identifier forSectionController: (nonnull IGListSectionController *) sectionController atIndex:(NSInteger)index;
Parameters
elementKind
The kind of supplementary view.
identifier
The identifier of the supplementary view in storyboard.
sectionController
The section controller requesting this information.
index
The index of the supplementary view.
Return Value
A supplementary view dequeued from the reuse pool or a newly created one.
-
Dequeues a supplementary view from the collection view reuse pool.
Note
This method uses a string representation of the view class as the identifier.
Declaration
Objective-C
- (nonnull __kindof UICollectionReusableView *) dequeueReusableSupplementaryViewOfKind:(nonnull NSString *)elementKind forSectionController: (nonnull IGListSectionController *)sectionController nibName:(nonnull NSString *)nibName bundle:(nullable NSBundle *)bundle atIndex:(NSInteger)index;
Parameters
elementKind
The kind of supplementary view.
sectionController
The section controller requesting this information.
nibName
The name of the nib file.
bundle
The bundle in which to search for the nib file. If
nil
, this method searches the main bundle.index
The index of the supplementary view.
Return Value
A supplementary view dequeued from the reuse pool or a newly created one.
-
Invalidate the backing
UICollectionViewLayout
for all items in the section controller.Note
This method can be wrapped in
UIView
animation APIs to control the duration or perform without animations. This will end up calling-[UICollectionView performBatchUpdates:completion:]
internally, so invalidated changes may not be reflected in the cells immediately.Declaration
Objective-C
- (void)invalidateLayoutForSectionController: (nonnull IGListSectionController *)sectionController completion: (nullable void (^)(BOOL))completion;
Parameters
sectionController
The section controller that needs invalidating.
completion
An optional completion block to execute when the updates are finished.
-
Batches and performs many cell-level updates in a single transaction.
Note
You should make state changes that impact the number of items in your section controller within the updates block alongside changes on the context object.
For example, inside your section controllers, you may want to delete and insert into the data source that backs your section controller. For example:
[self.collectionContext performBatchItemUpdates:^ (id<IGListBatchContext> batchContext>){ // perform data source changes inside the update block [self.items addObject:newItem]; [self.items removeObjectAtIndex:0]; NSIndexSet *inserts = [NSIndexSet indexSetWithIndex:[self.items count] - 1]; [batchContext insertInSectionController:self atIndexes:inserts]; NSIndexSet *deletes = [NSIndexSet indexSetWithIndex:0]; [batchContext deleteInSectionController:self atIndexes:deletes]; } completion:nil];
Warning
You must perform data modifications inside the update block. Updates will not be performed synchronously, so you should make sure that your data source changes only when necessary.Declaration
Objective-C
- (void) performBatchAnimated:(BOOL)animated updates:(nonnull void (^)(id<IGListBatchContext> _Nonnull))updates completion:(nullable void (^)(BOOL))completion;
Parameters
animated
A flag indicating if the transition should be animated.
updates
A block with a context parameter to make mutations.
completion
An optional completion block to execute when the updates are finished.
-
Scrolls to the specified section controller in the list.
Declaration
Objective-C
- (void)scrollToSectionController: (nonnull IGListSectionController *)sectionController atIndex:(NSInteger)index scrollPosition:(UICollectionViewScrollPosition)scrollPosition animated:(BOOL)animated;
Parameters
sectionController
The section controller.
index
The index of the item in the section controller to which to scroll.
scrollPosition
An option that specifies where the item should be positioned when scrolling finishes.
animated
A flag indicating if the scrolling should be animated.