DataSource

DataSource is a Swift framework that helps you specify, display and manipulate sectioned collections of items in UITableview and UICollectionView in an MVVM (Model-View-ViewModel) fashion without having to deal with index mapping or writing repetitive and error-prone code to handle and display changes of those collections.

DataSource framework introduces a DataSource protocol that specifies a provider of items grouped into sections just like a UITableViewDataSource is a provider of UITableViewCells or a UICollectionViewDataSource is a provider of UICollectionViewCells. A data source for a UITableView or a UICollectionView can be constructed by combining a DataSource with a common routine that provides a cell for each item.

Requirements

• iOS 8.0+
• Xcode 10.2+
• ReactiveSwift

Installation

The recommended way to add DataSource to your project is with Carthage. Add github "Fueled/DataSource" line to your Cartfile and proceed with your favorite way to update and integrate your Carthage dependencies.

Example Project

You will find examples of using DataSource framework in DataSourceExample project.

Rationale

DataSource is decoupled from any view-layer logic and contains only model or view-model items that in turn serve as view-models for corresponding cells. Such decoupling allows usage of same DataSource for both table and collection views as well as compositing several DataSources into a single CompositeDataSource object without having to deal with view-related logic.

DataSource composition

CompositeDataSource is one of the implementations of DataSource protocol. It is initialized with an array of inner DataSources. The sections of a CompositeDataSource are sections of the first inner DataSource, followed by sections of the second inner DataSource, etc.

Propagating changes

DataSource protocol exposes a Signal of DataChanges that can be subscribed for in order to update associated UITableView or UICollectionView when the underlying data changes.

DataChange is a simple protocol that comes with a set of implementations for insertion, deletion and reloading of items and sections as well as DataChangeReloadData and DataChangeBatch for handling multiple DataChanges at once.

CompositeDataSource automatically merges changes from inner DataSources and properly maps the indices of all DataChanges. This means that corresponding sections of UITableView or UICollectionView are updated whenever any of the inner DataSources emit changes.

Populating UITableView

DataSource framework contains a TableViewDataSource class that implements UITableViewDataSource protocol and can be used to populate an associated UITableView with data from any DataSource. TableViewDataSource receives and handles all DataChanges automatically.

TableViewDataSource expects your instances of UITableViewCell and UITableViewHeaderFooterView to conform to DataSourceItemReceiver protocol. This protocol contains ds_setItem: function that is used to populate those views with corresponding data source items. TableViewCell is a subclass of UITableViewCell that already implements DataSourceItemReceiver protocol by populating its MutableProperty called cellModel. Cells and views implemented in Objective-C can alternatively conform to @objc protocol DataSourceObjectItemReceiver with the restriction that items must be objects (of AnyObject type).

Just make TableViewDataSource instance a dataSource of your UITableView, connect the UITableView to tableView outlet of TableViewDataSource and assing your DataSource instance to TableViewDataSource’s dataSource.innerDataSource property.

If you have only one cell prototype in your UITableView you can use ”DefaultCell” for its reuseIdentifier. Otherwise, set TableViewDataSource’s reuseIdentifierForItem property to a block that returns an appropriate reuse identifier of a given item at a given index path.

TableViewDataSourceWithHeaderFooterTitles and TableViewDataSourceWithHeaderFooterViews subclasses can be used to provide either titles or views for section headers and footers.

You can subclass TableViewDataSource or any of its sublcasses to extend or override any UITableViewDataSource-related logic.

Populating UICollectionView

UICollectionView can be populated from a DataSource instance by using CollectionViewDataSource class in the same way UITableView is populated from a TableViewDataSource.

Implementations for other collection-displaying views (e.g. map views with annotations) can be crafted in a similar fashion.

Using with CoreData, KVO and others

DataSource protocol can be used to wrap any API that provides a collection of items and notifies of any changes of that collection.

DataSource framework provides implementations for two such collection-based APIs:

1. FetchedResultsDataSource class implements DataSource protocol using NSFetchedResultsController for CoreData models. FetchedResultsDataSource can be used just as any other DataSource without the need to manually implement NSFetchedResultsControllerDelegate protocol.
2. KVODataSource implements Key-Value Observing (KVO) for ordered to-many relationships.

In case you need to handle data changes provided by other sources e.g. Photos framework or the new Contacts framework, similar DataSource implementations can be easily crafted.