swift3 - iOS 10 中的 UICollectionView 预取数据源？

Question

prefetchDataSources的目的是什么在 iOS 10 中引入？

我刚刚在 XCode 8 GM Seed 中运行了一个项目并开始出现错误:

MessagesExtension[17902:1238603] *** Assertion failure in -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:applyAttributes:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit_Sim/UIKit-3599.6/UICollectionView.m:2161

Answer 1

UICollectionView gains a new property this year called prefetchDataSource. Just like the existing delegate and dataSource properties, we can simply set it to some object that implements the new UICollectionViewDataSourcePrefetching protocol.

这个协议(protocol)在 iOS 10 中是全新的，只需要我们实现一个新功能:

public func collectionView(_ collectionView: UICollectionView, prefetchItemsAt indexPaths: [IndexPath])

When this function is called, we can examine the indexPaths array we're passed in to know which cells are "coming up soon" and thus which cells we should probably begin loading the data for.

有关示例的详细理解，请参阅链接
UICollectionViewDataSourcePrefetching