CKCollectionViewDataSource Class Reference

Inherits from NSObject
Declared in CKCollectionViewDataSource.h

Overview

This class is an implementation of a UICollectionViewDataSource that can be used along with components. For each set of changes (i.e insertion/deletion/update of items and/or insertion/deletion of sections) the datasource will compute asynchronously on a background thread the corresponding component trees and then apply the corresponding UI changes to the collection view leveraging automatically view reuse.

Doing so this reverses the traditional approach for a UICollectionViewDataSource. Usually the controller layer will tell the UICollectionView to update and then the UICollectionView ask the datasource for the data. Here the model is more Reactive, from an external prospective, the datasource is told what changes to apply and then tell the collection view to apply the corresponding changes.

– initWithCollectionView:supplementaryViewDataSource:componentProvider:context:cellConfigurationFunction:

Designated initializer

- (instancetype)initWithCollectionView:(UICollectionView *)collectionView supplementaryViewDataSource:(id<CKSupplementaryViewDataSource>)supplementaryViewDataSource componentProvider:(Class<CKComponentProvider>)componentProvider context:(id<NSObject>)context cellConfigurationFunction:(CKCellConfigurationFunction)cellConfigurationFunction

Parameters

supplementaryViewDataSource

@see the supplementaryViewDataSource property. Will be held weakly, pass nil if you don’t need supplementary views.

componentProvider

Class implementing the pure function turning a model into components.@see CKComponentProvider.

context

Will be passed to your componentProvider. @see CKComponentProvider.

cellConfigurationFunction

Pointer to a function applying custom configuration to the UICollectionViewCell where the component tree is mounted. We use a function pointer and not a block to enforce the purity of said function.

Discussion

Warning: Reuse won’t be handled for you when modifying view parameters through this function, reserve it for small configurations.

Declared In

CKCollectionViewDataSource.h

– enqueueChangeset:constrainedSize:

Method to enqueue commands in the datasource.

- (void)enqueueChangeset:(const CKArrayControllerInputChangeset &)changeset constrainedSize:(const CKSizeRange &)constrainedSize

Parameters

changeset

The set of commands to apply to the collection view, e.g : ` CKArrayControllerSections sections; CKArrayControllerInputItems items; sections.insert(1); // Insert section at index 1 items.insert({1,0}, modelX); // Insert a row at index 0 in section 1 containing the UI corresponding to modelX item.update({0,0}, modelY); // Update row at index 0 in section 0 using modelY [_dataSource enqueueChangeset:{sections, items} constrainedSize:{{0,0},{50,50}}];

constrainedSize

The constrained size {{minWidth, minHeight},{maxWidth, maxHeight}} that will be used to compute your component tree.

Discussion

Warning: In a batch update: - deletes are applied first relatively to the index space before the batch update - inserts are then applied relatively to the “post deletion” index space: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UICollectionView_class/#//apple_ref/occ/instm/UICollectionView/performBatchUpdates:completion: `

Declared In

CKCollectionViewDataSource.h

– updateContextAndEnqueueReload:

Updates context to the new value and enqueues update changeset in order to rebuild component tree.

- (void)updateContextAndEnqueueReload:(id)newContext

Declared In

CKCollectionViewDataSource.h

– modelForItemAtIndexPath:

The model associated with a certain index path in the collectionView.

- (id<NSObject>)modelForItemAtIndexPath:(NSIndexPath *)indexPath

Return Value

The model associated with a certain index path in the collectionView.

As stated above components are generated asynchronously and on a backgorund thread. This means that a changeset is enqueued and applied asynchronously when the corresponding component tree is generated. For this reason always use this method when you want to retrieve the model associated to a certain index path in the table view (e.g in didSelectRowAtIndexPath: )

Declared In

CKCollectionViewDataSource.h

– sizeForItemAtIndexPath:

The layout size of the component tree at a certain indexPath. Use this to access the component sizes for instance in a UICollectionViewLayout(s) or in a UICollectionViewDelegateFlowLayout.

- (CGSize)sizeForItemAtIndexPath:(NSIndexPath *)indexPath

Return Value

The layout size of the component tree at a certain indexPath. Use this to access the component sizes for instance in a UICollectionViewLayout(s) or in a UICollectionViewDelegateFlowLayout.

Declared In

CKCollectionViewDataSource.h

– announceWillAppearForItemInCell:

Sends -componentTreeWillAppear to all CKComponentControllers for the given cell. If needed, call this from -collectionView:willDisplayCell:forItemAtIndexPath:

- (void)announceWillAppearForItemInCell:(UICollectionViewCell *)cell

Declared In

CKCollectionViewDataSource.h

– announceDidDisappearForItemInCell:

Sends -componentTreeDidDisappear to all CKComponentControllers for the given cell. If needed, call this from -collectionView:didEndDisplayingCell:forItemAtIndexPath:

- (void)announceDidDisappearForItemInCell:(UICollectionViewCell *)cell

Declared In

CKCollectionViewDataSource.h

  supplementaryViewDataSource

Supplementary views are not handled with components; the datasource will forward any call to collectionView:viewForSupplementaryElementOfKind:atIndexPath to this object.

@property (readonly, nonatomic, weak) id<CKSupplementaryViewDataSource> supplementaryViewDataSource

Declared In

CKCollectionViewDataSource.h