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Sauce

Sauce allows you to write simple, reusable collection view data sources. It is a work in progress. I use it in a production app, but the API is quite quirky and has some limitations. When used correctly, it makes complex collection view sources easy to build. Use with care.

Usage

Subclass SauceFlowLayoutController for your controller. Create data sources by either implementing DataSource or subclassing one of the existing sources (probably ArrayDataSource). Other sources can be used to alter or compose existing sources.

Implement registerReusableViewsWith(_:) to register your sources cell types with the collection view. Implement metricsForSection(_:collectionView:layout:) and metricsForItemAt(_:collectionView:layout:) to provide layout information. Be aware that currently, these two can be called many times, so they should be cheap (cache calculated sizes if necessary).

Sources

  • ArrayDataSource: Backed by an array. One cell per item. Implement loadInitialItems() and collectionView(_:cellForItem:atIndexPath:).
  • ComposedDataSource: Concatenates multiple sources. Use as is or subclass.
  • FilteredDataSource: Filters cells of a wrapped source. Implement and pass a Filter.

Pitfalls

Index paths passed into your sources methods are local to you index source. If you put multiple sources into a ComposedDataSource, each one will still get IndexPath(0, 0) for its first item.

If you need to pass index paths to the collection view (e.g. for dequeueing cells), pass them through globalIndexPath(_:) first. If it returns nil, the cell is not actually visible to the collection view (e.g. it may be filtered out).