CollectionView Delegate

func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool

func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool

func collectionView(_ collectionView: UICollectionView, shouldDeselectItemAt indexPath: IndexPath) -> Bool 

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, willDisplaySupplementaryView view: UICollectionReusableView, forElementKind elementKind: String, at indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, didEndDisplayingSupplementaryView view: UICollectionReusableView, forElementOfKind elementKind: String, at indexPath: IndexPath)

func collectionView(_ collectionView: UICollectionView, shouldShowMenuForItemAt indexPath: IndexPath) -> Bool

func collectionView(_ collectionView: UICollectionView, canPerformAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) -> Bool

func collectionView(_ collectionView: UICollectionView, performAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?)

func collectionView(_ collectionView: UICollectionView, transitionLayoutForOldLayout fromLayout: UICollectionViewLayout, newLayout toLayout: UICollectionViewLayout) -> UICollectionViewTransitionLayout

func collectionView(_ collectionView: UICollectionView, canFocusItemAt indexPath: IndexPath) -> Bool

func collectionView(_ collectionView: UICollectionView, shouldUpdateFocusIn context: UICollectionViewFocusUpdateContext) -> Bool

func collectionView(_ collectionView: UICollectionView, didUpdateFocusIn context: UICollectionViewFocusUpdateContext, with coordinator: UIFocusAnimationCoordinator)

func indexPathForPreferredFocusedView(in collectionView: UICollectionView) -> IndexPath?

func collectionView(_ collectionView: UICollectionView, targetIndexPathForMoveFromItemAt originalIndexPath: IndexPath, toProposedIndexPath proposedIndexPath: IndexPath) -> IndexPath

func collectionView(_ collectionView: UICollectionView, targetContentOffsetForProposedContentOffset proposedContentOffset: CGPoint) -> CGPoint 

func collectionView(_ collectionView: UICollectionView, shouldSpringLoadItemAt indexPath: IndexPath, with context: UISpringLoadedInteractionContext) -> Bool

func collectionView(_ collectionView: UICollectionView, shouldBeginMultipleSelectionInteractionAt indexPath: IndexPath) -> Bool

func collectionView(_ collectionView: UICollectionView, didBeginMultipleSelectionInteractionAt indexPath: IndexPath)

func collectionViewDidEndMultipleSelectionInteraction(_ collectionView: UICollectionView)

func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration?
    
func collectionView(_ collectionView: UICollectionView, previewForHighlightingContextMenuWithConfiguration configuration: UIContextMenuConfiguration) -> UITargetedPreview?

func collectionView(_ collectionView: UICollectionView, previewForDismissingContextMenuWithConfiguration configuration: UIContextMenuConfiguration) -> UITargetedPreview?

func collectionView(_ collectionView: UICollectionView, willPerformPreviewActionForMenuWith configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionCommitAnimating)

func collectionView(_ collectionView: UICollectionView, willDisplayContextMenu configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionAnimating?)

func collectionView(_ collectionView: UICollectionView, willEndContextMenuInteraction configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionAnimating?)

DelegateFlowLayout protocol

// cell의 사이즈를 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize

//섹션의 inset(margin)을 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets

//특정 섹션의 row나 column들간의 spacing을 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat

//특정 섹션의 item들간의 spacing을 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat

//특정 섹션의 Header View의 사이즈를 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize

//특정 섹션의 Footer View의 사이즈를 어떻게 할까?
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize