AsyncDisplayKit/_docs/containers-ascollectionnode.md

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ASCollectionNode is equivalent to UIKit's UICollectionView and can be used in place of any UICollectionView.

ASCollectionNode replaces UICollectionView's required method

collectionView:cellForItemAtIndexPath:

with your choice of one of the following methods

- (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForItemAtIndexPath:(NSIndexPath *)indexPath

or

- (ASCellNodeBlock)collectionView:(ASCollectionView *)collectionView nodeBlockForItemAtIndexPath:(NSIndexPath *)indexPath (recommended)

Note that these are the same methods as the `ASTableNode`! Please read the previous `ASTableNode` section as most of the details here are identical and so we will gloss over them quickly.

As noted in the previous section

• both of these ASCollectionView methods should not implement reuse (they will be called once per row)
• `collectionView:nodeBlockForRowAtIndexPath:` is preferred to `collectionView:nodeForItemAtIndexPath:` for its concurrent processing
• it is very important that node blocks be thread-safe
• ASCellNodes are used by ASTableNode, ASCollectionNod and ASPagerNode

##Replace UICollectionViewController with ASViewController##

AsyncDisplayKit does not offer an equivalent to UICollectionViewController. Instead, use an ASViewController initialized with an ASCollectionNode.

Consider, the ASViewController subclass - LocationCollectionNodeController - from the ASDKgram sample app that uses a collection node as its managed node.

An ASCollectionNode is assigned to be managed by an ASViewController in its initWithNode: designated initializer method.

- (instancetype)initWithCoordinates:(CLLocationCoordinate2D)coordinates
{
  _flowLayout     = [[UICollectionViewFlowLayout alloc] init];
  _collectionNode = [[ASCollectionNode alloc] initWithCollectionViewLayout:_flowLayout];
  
  self = [super initWithNode:_collectionNode];
  if (self) {
    _flowLayout.minimumInteritemSpacing  = 1;
    _flowLayout.minimumLineSpacing       = 1;
  }
  
  return self;
}

##Accessing the ASCollectionView## If you've used previous versions of ASDK, you'll notice that ASCollectionView has been removed in favor of ASCollectionNode.

`ASCollectionView` (an actual UICollectionView subclass) is still used as an internal property of `ASCollectionNode`. While it should not be created directly, it can still be used directly by accessing the .view property of an `ASCollectionNode`.

Do not forget that anything that accesses a view using AsyncDisplayKit's node containers or nodes should be done in viewDidLoad or didLoad, respectively.

The LocationCollectionNodeController above accesses the ASCollectionView directly in viewDidLoad

- (void)loadView
{
  [super loadView];
  
  _collectionNode.view.asyncDelegate   = self;
  _collectionNode.view.asyncDataSource = self;
  _collectionNode.view.allowsSelection = NO;
  _collectionNode.view.backgroundColor = [UIColor whiteColor];
}

##Table Row Height##

As discussed in the previous ASTableNode section, ASCollectionNodes and ASTableNodes do not need to keep track of the height of their ASCellNodes.

***constrainedSizeForNode (also in table, but more important for collection) - check that (0,0) min and (infinity, infinity) max

• example sample photo grid
  • popover, rotated -> how to get size constraint (USE constrainedSizeForNode to do simple divide by 3 width thing)
• document itemSize (check what happens in ASDKgram)

##Sample Apps with ASCollectionNodes##

• ASDKgram
• CatDealsCollectionView
• ASCollectionView