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
   

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2. PHOTOS, PHOTOS, MORE PHOTOS
   • SEARCH
   • NEW FEED
   • COLLECTION
   • PHOTOGRAPHER
   

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3. SAME THING
   DIFFERENT SOURCE
   

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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]?
   }
   

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5. THEN
   SUBCLASSES
   • For each API endpoint that uses paging
   • For photos and collections
   

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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
   }
   

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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)
   }
   

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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)
   ...
   }
   

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9. FACTORY BONUS
   IT CREATES THE DATA SOURCE
   var dataSource: PagedDataSource {
   return PagedDataSource(with: self)
   }
   

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10. OK, BUT HOW TO USE THIS?
    The PhotosViewController uses a data source:
    var dataSource: PagedDataSource
    Which is set as easily as this:
    photosViewController.dataSource =
    PhotosDataSourceFactory.search(query:”summer").dataSource
    

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11. HOPE YOU ENJOYED
    QUESTIONS?
    

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12. 
    Olivier Collet
    1-man wolf pack building all the native apps at Unsplash
    @ocollet
    

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