Enum Factories And Generic Data Sources

Presented at CocoaHeads Montreal on November 16th, 2017.

Transcript

1. ENUM FACTORIES AND GENERIC DATA SOURCES OLIVIER COLLET. COCOAHEADS MONTREAL. 16.11.2017
2. PHOTOS, PHOTOS, MORE PHOTOS • SEARCH • NEW FEED • COLLECTION • PHOTOGRAPHER
3. SAME THING DIFFERENT SOURCE
4. IT STARTS WITH A PAGED REQUEST I’ll spare you the details. The most important thing is this: struct Cursor { let page: Int let perPage: Int let parameters: [String: Any]? }
5. THEN SUBCLASSES • For each API endpoint that uses paging • For photos and collections
6. LET’S MOVE TO THE STUFF THE DATA SOURCE • It uses generics to handle photos and collections • It uses a factory to generate cursors and requests protocol PagedDataSourceFactory { func initialCursor() -> Cursor func request(with cursor: Cursor) -> PagedRequest }
7. SO WHAT ABOUT THE FACTORY? THAT’S WHERE IT GETS REALLY enum PhotosDataSourceFactory: PagedDataSourceFactory { case photos(order: GetPhotosRequest.Order) case trending case search(query: String) case collection(identifier: String, curated: Bool) }
8. WHAT ABOUT THAT PROTOCOL? IT’S GETTING func initialCursor() -> PagedRequest.Cursor { switch self { case .photos(let order): return GetPhotosRequest.cursor(with: order, page: 1, perPage: 20) case .trending: return GetHomePhotosRequest.cursor(with: nil) case .search(let query): return SearchPhotosRequest.cursor(with: query, page: 1, perPage: 20) ... } func request(with cursor: PagedRequest.Cursor) -> PagedRequest { switch self { case .photos(let order): return GetPhotosRequest(orderBy: order, page: cursor.page, perPage: cursor.perPage) case .trending: return GetHomePhotosRequest(with: cursor) case .search(let query): return SearchPhotosRequest(with: query, page: cursor.page, perPage: cursor.perPage) ... }
9. FACTORY BONUS IT CREATES THE DATA SOURCE var dataSource: PagedDataSource<Photo> { return PagedDataSource<Photo>(with: self) }
10. OK, BUT HOW TO USE THIS? The PhotosViewController uses a data source: var dataSource: PagedDataSource<Photo> Which is set as easily as this: photosViewController.dataSource = PhotosDataSourceFactory.search(query:”summer").dataSource
11. HOPE YOU ENJOYED QUESTIONS?
12. Olivier Collet 1-man wolf pack building all the native apps at Unsplash @ocollet