IGListCollectionContext Protocol Reference


                    
                    
                    containerSize

The size of the collection view. You can use this for sizing cells.

Declaration

Objective-C

@property (nonatomic, readonly) CGSize containerSize;

Swift

var containerSize: CGSize { get }


                    
                    
                    containerInset

The content insets of the collection view. You can use this for sizing cells.

Declaration

Objective-C

@property (nonatomic, readonly) UIEdgeInsets containerInset;

Swift

var containerInset: UIEdgeInsets { get }


                    
                    
                    adjustedContainerInset

The adjusted content insets of the collection view. Equivalent to containerInset under iOS 11.

Declaration

Objective-C

@property (nonatomic, readonly) UIEdgeInsets adjustedContainerInset;

Swift

var adjustedContainerInset: UIEdgeInsets { get }


                    
                    
                    insetContainerSize

The size of the collection view with content insets applied.

Declaration

Objective-C

@property (nonatomic, readonly) CGSize insetContainerSize;

Swift

var insetContainerSize: CGSize { get }


                    
                    
                    containerContentOffset

The content offset of the collection view.

Declaration

Objective-C

@property (nonatomic, readonly) CGPoint containerContentOffset;

Swift

var containerContentOffset: CGPoint { get }


                    
                    
                    traitCollection

The trait collection of the collection view.

Declaration

Objective-C

@property (nonatomic, readonly, nullable) UITraitCollection *traitCollection;

Swift

var traitCollection: UITraitCollection? { get }


                    
                    
                    scrollingTraits

The current scrolling traits of the underlying collection view.

Declaration

Objective-C

@property (nonatomic, readonly) IGListCollectionScrollingTraits scrollingTraits;

Swift

var scrollingTraits: IGListCollectionScrollingTraits { get }


                    
                    
                    experiments

A bitmask of experiments to conduct on the section controller.

Declaration

Objective-C

@property (nonatomic) IGListExperiment experiments;

Swift

var experiments: IGListExperiment { get set }


                    
                    
                    -containerSizeForSectionController:

Returns size of the collection view relative to the section controller.

Declaration

Objective-C

- (CGSize)containerSizeForSectionController:
    (nonnull IGListSectionController *)sectionController;

Swift

func containerSize(for sectionController: IGListSectionController) -> CGSize

Parameters


                                sectionController

The section controller requesting this information.

Return Value

The size of the collection view minus the given section controller’s insets.


                    
                    
                    -indexForCell:sectionController:

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;

Swift

func index(for cell: UICollectionViewCell, sectionController: IGListSectionController) -> Int

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.


                    
                    
                    -cellForItemAtIndex:sectionController:

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;

Swift

func cellForItem(at index: Int, sectionController: IGListSectionController) -> UICollectionViewCell?

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.


                    
                    
                    -viewForSupplementaryElementOfKind:atIndex:sectionController:

Returns the supplementary view 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 UICollectionReusableView *)
    viewForSupplementaryElementOfKind:(nonnull NSString *)elementKind
                              atIndex:(NSInteger)index
                    sectionController:
                        (nonnull IGListSectionController *)sectionController;

Swift

func viewForSupplementaryElement(ofKind elementKind: String, at index: Int, sectionController: IGListSectionController) -> UICollectionReusableView?

Parameters

`elementKind`	The element kind of the supplementary view.
`index`	The index of the desired cell.
`sectionController`	The section controller requesting this information.

Return Value

The collection reusable view, or nil if not found.


                    
                    
                    -fullyVisibleCellsForSectionController:

Returns the fully visible cells for the given section controller.

Declaration

Objective-C

- (nonnull NSArray<UICollectionViewCell *> *)
    fullyVisibleCellsForSectionController:
        (nonnull IGListSectionController *)sectionController;

Swift

func fullyVisibleCells(for sectionController: IGListSectionController) -> [UICollectionViewCell]

Parameters


                                sectionController

The section controller requesting this information.

Return Value

An array of fully visible cells, or an empty array if none are found.


                    
                    
                    -visibleCellsForSectionController:

Returns the visible cells for the given section controller.

Declaration

Objective-C

- (nonnull NSArray<UICollectionViewCell *> *)visibleCellsForSectionController:
    (nonnull IGListSectionController *)sectionController;

Swift

func visibleCells(for sectionController: IGListSectionController) -> [UICollectionViewCell]

Parameters


                                sectionController

The section controller requesting this information.

Return Value

An array of visible cells, or an empty array if none are found.


                    
                    
                    -visibleIndexPathsForSectionController:

Returns the visible paths for the given section controller.

Declaration

Objective-C

- (nonnull NSArray<NSIndexPath *> *)visibleIndexPathsForSectionController:
    (nonnull IGListSectionController *)sectionController;

Swift

func visibleIndexPaths(for sectionController: IGListSectionController) -> [IndexPath]

Parameters


                                sectionController

The section controller requesting this information.

Return Value

An array of visible index paths, or an empty array if none are found.


                    
                    
                    -deselectItemAtIndex:sectionController:animated:

Deselects a cell in the collection.

Declaration

Objective-C

- (void)deselectItemAtIndex:(NSInteger)index
          sectionController:(nonnull IGListSectionController *)sectionController
                   animated:(BOOL)animated;

Swift

func deselectItem(at index: Int, sectionController: IGListSectionController, animated: Bool)

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.


                    
                    
                    -selectItemAtIndex:sectionController:animated:scrollPosition:

Selects a cell in the collection.

Declaration

Objective-C

- (void)selectItemAtIndex:(NSInteger)index
        sectionController:(nonnull IGListSectionController *)sectionController
                 animated:(BOOL)animated
           scrollPosition:(UICollectionViewScrollPosition)scrollPosition;

Swift

func selectItem(at index: Int, sectionController: IGListSectionController, animated: Bool, scrollPosition: UICollectionView.ScrollPosition)

Parameters

`index`	The index of the item to select.
`sectionController`	The section controller requesting this information.
`animated`	Pass `YES` to animate the change, `NO` otherwise.
`scrollPosition`	An option that specifies where the item should be positioned when scrolling finishes.


                    
                    
                    -dequeueReusableCellOfClass:withReuseIdentifier:forSectionController:atIndex:

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
           withReuseIdentifier:(nullable NSString *)reuseIdentifier
          forSectionController:
              (nonnull IGListSectionController *)sectionController
                       atIndex:(NSInteger)index;

Swift

func dequeueReusableCell(of cellClass: AnyClass, withReuseIdentifier reuseIdentifier: String?, for sectionController: IGListSectionController, at index: Int) -> UICollectionViewCell

Parameters

`cellClass`	The class of the cell you want to dequeue.
`reuseIdentifier`	A reuse identifier for the specified cell. This parameter may be `nil`.
`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.


                    
                    
                    -dequeueReusableCellOfClass:forSectionController:atIndex:

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;

Swift

func dequeueReusableCell(of cellClass: AnyClass, for sectionController: IGListSectionController, at index: Int) -> UICollectionViewCell

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.


                    
                    
                    -dequeueReusableCellWithNibName:bundle:forSectionController:atIndex:

Dequeues a cell from the collection view reuse pool.

Note

This method uses the nib name as the reuse identifier.

Declaration

Objective-C

- (nonnull __kindof UICollectionViewCell *)
    dequeueReusableCellWithNibName:(nonnull NSString *)nibName
                            bundle:(nullable NSBundle *)bundle
              forSectionController:
                  (nonnull IGListSectionController *)sectionController
                           atIndex:(NSInteger)index;

Swift

func dequeueReusableCell(withNibName nibName: String, bundle: Bundle?, for sectionController: IGListSectionController, at index: Int) -> UICollectionViewCell

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.


                    
                    
                    -dequeueReusableCellFromStoryboardWithIdentifier:forSectionController:atIndex:

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;

Swift

func dequeueReusableCellFromStoryboard(withIdentifier identifier: String, for sectionController: IGListSectionController, at index: Int) -> UICollectionViewCell

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.


                    
                    
                    -dequeueReusableSupplementaryViewOfKind:forSectionController:class:atIndex:

Dequeues a supplementary view from the collection view reuse pool.

Note

This method uses a string representation of the view class and the kind as the identifier.

Declaration

Objective-C

- (nonnull __kindof UICollectionReusableView *)
    dequeueReusableSupplementaryViewOfKind:(nonnull NSString *)elementKind
                      forSectionController:
                          (nonnull IGListSectionController *)sectionController
                                     class:(nonnull Class)viewClass
                                   atIndex:(NSInteger)index;

Swift

func dequeueReusableSupplementaryView(ofKind elementKind: String, for sectionController: IGListSectionController, class viewClass: AnyClass, at index: Int) -> UICollectionReusableView

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.


                    
                    
                    -dequeueReusableSupplementaryViewFromStoryboardOfKind:withIdentifier:forSectionController:atIndex:

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;

Swift

func dequeueReusableSupplementaryView(fromStoryboardOfKind elementKind: String, withIdentifier identifier: String, for sectionController: IGListSectionController, at index: Int) -> UICollectionReusableView

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.


                    
                    
                    -dequeueReusableSupplementaryViewOfKind:forSectionController:nibName:bundle:atIndex:

Dequeues a supplementary view from the collection view reuse pool.

Note

This method uses the nib name as the reuse 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;

Swift

func dequeueReusableSupplementaryView(ofKind elementKind: String, for sectionController: IGListSectionController, nibName: String, bundle: Bundle?, at index: Int) -> UICollectionReusableView

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.


                    
                    
                    -invalidateLayoutForSectionController:completion:

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;

Swift

func invalidateLayout(for sectionController: IGListSectionController) async -> Bool

Parameters

`sectionController`	The section controller that needs invalidating.
`completion`	An optional completion block to execute when the updates are finished.


                    
                    
                    -performBatchAnimated:updates:completion:

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;

Swift

func performBatch(animated: Bool, updates: @escaping (any ListBatchContext) -> Void) async -> Bool

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.


                    
                    
                    -scrollToSectionController:atIndex:scrollPosition:animated:

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;

Swift

func scroll(to sectionController: IGListSectionController, at index: Int, scrollPosition: UICollectionView.ScrollPosition, animated: Bool)

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.